Construction Updates (basic)

BITUMEN

2012-02-25T17:29:00.001-08:00

· DEFINITION:

A non-crystalline solid or viscous material having adhesive properties derived from petroleum either by natural or refinery processes, and substantially soluble in carbon disulphide. Bitumen is black or brown in colour. This may occur naturally but are usually made as end products from distillation of, or extracts from, selected petroleum oils.

· NOMENCLATURE:

Bitumen and asphalt are both generic terms. In USA, the word asphalt is used as synonymous with bitumen- the refinery product which has now largely replaced the natural asphalts that occur in Trinidad, Venezuela, Cuba etc. Outside USA however, the word asphalt is generally taken to mean a mixture of refinery bitumen with a substantial proportion of solid mineral matter.

· SOURCES:

· Bitumen does occur naturally, but for all intents and purposes it is petroleum on which the world relies for its supplies of bitumen today. The bitumen content of crude can vary between 15% and 80%, but the more normal range is 25% to 40%.

· In fact the three broad classifications for crude oils are:

1) Bitumen based

2) Paraffin based

3) Bitumen and paraffin based

· Depending on the type of crude, bitumen is present either in the form of colloidally dispersed particles or in a true solution. During the refining process, as petroleum oils are taken away by distillation, the proportion of oil to bitumen particles changes. Instead of being dispersed and relatively few in number, the particles become closer to one another and the size of the particles increases.

· At the point when the distillation process is usually stopped, the petroleum bitumen is a colloidal dispersion of black solids (hydrocarbons), known as asphaltenes, in a dispersion medium, which is an oily brown yellow liquid known as malthene fraction. Also present to act as a stabilizing agent to keep the asphaltenes in suspension are another group of hydrocarbons known as resins.

· Bitumen is found in nature in several forms, from the hard, easily crumbled bitumen in rock asphalt to the softer, more viscous material found in tar sands and asphalt 'lakes'. It is commonly mixed with varying proportions of mineral or vegetable impurities that need to be extracted before it can be used effectively as an engineering material.

· However it may be found as an asphaltite, natural bitumen without impurities that varies in the extent to which it is soluble in carbon disulphide. Natural bitumen occurs, as does petroleum, as the result of the special decomposition of marine debris. It will have been moved over many thousands of years through porous rocks such as limestone or sandstone, often by volcanic action. In some areas notable for their petroleum resources, for example the Middle East, semi-fluid bitumen can be found oozing out of fissures near hot springs or seeping out of the ground.

· Rock asphalt, with its variable and relatively low content of bitumen, tends to be found away from the places where bitumen is needed. It is costly to move around and to process. It is important to draw the distinction between bitumen and coal tar. The latter is obtained from the carbonization of coal and, although it is black and viscous in appearance,it has very different chemical properties.

· Engineering projects in every part of the world, from the construction of transcontinental highways to the waterproofing of flat roof surfaces, rely on the particular properties of bitumen. Crude oil processed by the petroleum industry provides all but a small percentage of this vital material.

· FIRST USE OF BITUMEN:

· The first recorded uses of asphalt as a road-building material in Bbylon.The ancient Greeks were also familiar with asphalt. The asphalt comes from the Greek “asphaltos” meaning “secure”. The Romans used it to seal their baths, reservoirs and aqueducts.

· But Main Contribution from U.S and Canada.

· COMPOSITION:

· On average, Bitumen is composed of:

Carbon - 83.2%

Hydrogen - 10.4%

Oxygen - 0.94%

Nitrogen - 0.36%

Sulphur - 4.8%

· The remaining content is made up of small quantities of methane and hydrogen sulphide, along with traces of nickel, iron and vanadium.

· TYPES OF BITUMEN:

· There are five major classifications of petroleum bitumen produced by the refining and manufacturing process:

1) Paving grade bitumen

2) Cutback bitumen

3) Bitumen emulsions

4) Industrial bitumen

5) Modified bitumen

6) Bitumen Binder Modifiers

· Paving Grade Bitumen:

It’s also called as Asphalt Cement & is refined and blended to meet road engineering and industrial specifications that take into account different climatic conditions. As a product it is the most widely used bitumen. It may also be considered as the parent bitumen from which the other types, listed below, are produced.

· Cutback Bitumen:

They consist basically of bitumen that has been diluted in order to make it more fluid for application, mainly in road making. Their fluidity depends on the degree of hardness of the bitumen base and the proportion of diluent (or flux) to bitumen. They are classified according to the time it takes them to become solid, as rapid curing (RC), medium curing (MC) or slow curing (SC) cutbacks. The cutback varies according to the flux, white spirit commonly being used for RC grades, kerosene for MC and diesel for SC. They set as the flux evaporates. This evaporation is currently regarded as a potentially undesirable characteristic from the point of view of the environment and health and safety, so cutback bitumen’s are looked upon less favorably than the more modem bitumen emulsions.

· Bitumen Emulsion:

§ The basic bitumen has also been diluted in order to facilitate application. Hot bitumen, water and emulsifier are processed in a high-speed colloid mill that disperses the bitumen in the water in the form of globules that are normally in the 5-10 micrometer size range but may be even smaller. The emulsifier produces a system in which fine droplets of bitumen, of between 30% and 80% of the volume, are held in suspension. If they separate in storage, the emulsion can easily be restored by agitation.

§ Bitumen emulsions have a low viscosity and can be workable at ambient temperatures, which makes them ideal for use in road building. This application requires controlled breaking and setting. The emulsion must not break before it is laid on the road surface but, once in place, it should break quickly so that the road can be in service again without delay. Particles of bitumen are dispersed in water to make bitumen emulsions are usually between 5 and 10 micrometers in size. This diagram gives an indication of relative size.

§ The mechanical performance of bitumen emulsions can be tailored like that of other construction materials.

And Bitumen emulsions are divided into three categories:

1) Anionic with negatively charged globules

2) Cationic with positively charged globules

3) Non-ionic with neutral globules.

The main grades for bitumen emulsions are classified as follows:

Anionic	Cationic
ARS	CRS	Rapid setting
AMS	CMS	Medium setting
ASS	CSS	Slow setting

§ The development of bitumen emulsions is an area where technological progress is still being made to meet engineering demands. The first emulsions were the anionics. They are currently less favoured than the cationics because the positively charged globules of bitumen coat the aggregates more thoroughly and have greater adhesion. Use of cationic emulsions is therefore increasing.

· Industrial bitumen:

These are also called as Oxidized Bitumen’s and these are made by blowing air through hot paving grade bitumen. The result is a product that softens at a higher temperature than that at which paving grade bitumen softens. It also has more rubber like properties and its viscosity is much less affected by changes in temperature than is the case with paving grade bitumen.

· Modified bitumen’s:

These are formulated with additives to improve their service performance by changing such properties as their durability, resistance to ageing, elasticity and/or plasticity. As well as natural rubbers, polymers such as styrene butadiene styrene (SBS), thermoplastic rubbers and ethylene vinyl acetate (EVA) are commonly used to modify bitumen and some companies, including BP, have their own proprietary technology using special polymers or polymer blends. This is an exciting development of growing importance due to the ability of modem technology to satisfy the demands of the bitumen market internationally. For example, polymers that extend the range of temperatures at which bitumen is worked will enable road builders to work effectively for more months of the year. A modified bitumen that increases the extent to which a road 'bounces back' after being subjected to heavy traffic, in terms of weight and volume, will contribute towards a longer road life and lower maintenance costs.

· Bitumen Binder Modifiers:

Some asphalt cements require modification in order to meet specifications. Asphalt cement modification has been practiced for over 50 years but has received added attention in the past decade or so. There are numerous binder additives available on the market today. The benefits of modified asphalt cement can only be realized by a judicious selection of the modifier(s); not all modifiers are appropriate for all applications. In general, asphalt cement should be modified to achieve the following types of improvements (Roberts et al., 1996):

· Lower stiffness (or viscosity) at the high temperatures associated with construction. This facilitates pumping of the liquid asphalt binder as well as mixing and compaction of HMA.

· Higher stiffness at high service temperatures. This will reduce rutting and shoving.

· Lower stiffness and faster relaxation properties at low service temperatures. This will reduce thermal cracking.

· Increased adhesion between the asphalt binder and the aggregate in the presence of moisture. This will reduce the likelihood of stripping. Figure 4 shows two aggregate samples from the same source after they have been coated with asphalt binder. The asphalt binder used with the sample on the left contain no anti-stripping modifier, which resulted in almost no aggregate-asphalt binder adhesion. The asphalt binder used with the sample on the right contains 0.5% (by weight of asphalt binder) of an anti-stripping modifier, which results in good aggregate-asphalt binder adhesion.

Figure 4: Effects of an Antistripping Modifier

· OTHER FORMS OF ASPHALT/BITUMEN USED IN PAVING:

Besides asphalt cement, three other forms of asphalt are used prominently in the paving industry:

· Emulsified asphalt. Emulsified asphalt is a suspension of small asphalt cement globules in water, which is assisted by an emulsifying agent (such as soap). Emulsions have lower viscosities than neat (plain) asphalt and can thus be used in low temperature applications. After an emulsion is applied the water evaporates away and only the asphalt cement is left. Emulsions are often used as prime coats and tack coats.

Cutback asphalt. A cutback asphalt is a combination of asphalt cement and petroleum solvent. Like emulsions, cutbacks are used because their viscosity is lower than that of neat asphalt and can thus be used in low temperature applications. After a cutback is applied the solvent evaporates away and only the asphalt cement is left. Cutbacks are much less common today because the petroleum solvent is more expensive than water and can be an environmental concern. Cutbacks are typically used as prime coats and tack coats.

Foamed asphalt. Foamed asphalt is formed by combining hot asphalt binder with small amounts of cold water. When the cold water comes in contact with the hot asphalt binder it turns to steam, which becomes trapped in tiny asphalt binder bubbles (World Highways, 2001). The result is a thin-film, high volume asphalt foam. This high volume foam state only lasts for a few minutes, after which the asphalt binder resumes its original properties. Foamed asphalt can be used as a binder in soil or base course stabilization, and is often used as the stabilizing agent in cold in-place recycling (CIPR).

· There is another type of Oxidized Bitumen Mainly Existing and Using in U.S,that is TIKI Bitumen

· In this too many varieties are there.

· Detailed explanation is as follows.

· Tiki Oxidized bitumen comply with International Standards. Tiki Oxidized bitumen has got a range of uses. It can be used in industries as an adhesive, protective coating, bonding agent, electric insulator and structures below ground. Because of their softening point, it shows excellent physical stability, no exudation or bleeding in contact with highly absorptive material and a remarkable resistance against atmospheric corrosion.

· Grades of Oxidized TIKI Bitumen:

85/25, 85/40, 90/15, 115/15, 135/10, 155/6

· Tiki Anti Stripping Agent:

Tiki Anti Stripping Agent is a highly stable anti stripping agent for increasing adhesion between asphalt and aggregates. It has been specifically designed for use in the manufacture of high performance emulsions, Cutbacks and hot mix. It may be used in polymer asphalt systems. It is NOT an amine and so is also useful as a bitumen additive.

Anti Stripping agent is ‘Heat Stable’ for 10 days at 1600C It have No smell, Non flammable, and contain no volatile solvents. It is liquid in nature and easy to use. It’s USE is recommended to avoid stripping even under submergence in water.

· Tiki Cut Back:

Tiki Cut Back Bitumen is a low viscosity, cold applied bituminous primer. Cutback Bitumen is produced by fluxing bitumen with distillates of petroleum for use in road construction. A bituminous prime coat is an initial application of low viscosity liquid material to an absorbent surface preparatory to any super-imposed treatment or construction. The object of priming is to promote adhesion between the existing surface and super-imposed treatment or construction. The choice of a bituminous primer shall depend upon the porosity characteristics of the surface to be primed. Cutback bitumen Primer is classified into Rapid Curing (RC), Medium Curing (MC) & Slow Curing (SC) based on viscosity.

· Tiki Bitumen(Paving Grade: 60/70 & 30/40):

Paving Bitumen shall be prepared by the distillation of suitable crude, petroleum oil without subsequent blending with other grades. The material shall be homogenous and shall not foam when heated to 175 deg C. No mineral matter other than naturally contained in the material shall be present.

Paving Bitumen (Straight Grade) used in construction and maintenance of Roads, Airfields & Allied Constructions.

· TIKI CRMB(Crumb Rubber Modified Bitumen):

TIKI CRMB is a blend of selected grades of bitumen and crumb rubber modifier. The modifier restores the required visco-elastic balance of the Bitumen binder, which improves binder resistance to any form of permanent deformation while maintaining high resistance to fatigue, thermal and low temperature cracking. When using TIKI CRMB, the maintenance free life of pavement will increase one and half to two times as compared to roads built using unmodified neat bitumen binders. TIKI CRMB has good adhesion to different types of aggregates which therefore reduce, rutting, cracking, deformations, etc. TIKI CRMB meets the performance- based specification of IRC: SP 53-2002.

· Advantages of TIKI CRMB:

· Excellent Resistance to Thermal and low temperature cracking.

· Superior resistance to any form to permanent deformation.

· Better adhesion between aggregate and binder.

· Overall improved performance in extreme climatic conditions.

· Higher fatigue life of mixes.

· Highly flexible and stability

· Cost effective.

· TIKI PMB(Polymer Modified Bitumen):

This invention relates to the process for the preparation of a polymer and rubber based modified binder which is useful for the construction of roads catering to heavy traffic and also for the formation of airfields and surfacings, besides its use as binder for stress absorbing membrane (SAM) and stress absorbing membrane interlayer (SAMI) for sealing of cracks, preventive maintenance of flexible pavement and delaying reflective cracking. Modified Bitumen performs better than ordinary Bitumen in high rain fall area and in situation where the aggregates are prone to stripping.

· Advantages of TIKI PMB:

· Improves resistance in cracking resulting in stronger and more durable overlays even in extreme climatic conditions.

· Reduces deformation on the roads even at temperatures of ( 50-70 degrees C)

· Polymer and Rubber based modifer binder extend life of pavement by 50-70% compared to conventional bitumen.

· PMB act as a multigrade bitumen and are economical when life cycle cost is taken into consideration.

· PROPERTIES OF ASPHALT OR BITUMEN:

“Asphalt" is a dark brown to black, highly viscous, hydrocarbon produced from petroleum distillation residue. This distillation can occur naturally, resulting in asphalt lakes, or occur in a petroleum refinery using crude oil. In 2001, the U.S. produced almost 35 million tons of asphalt at a rough value of around $6 billion. Roads and highways constitute the largest single use of asphalt at 85 percent of the total (Asphalt Institute, 2002). In HMA, asphalt functions as a waterproof, thermoplastic, viscoelastic adhesive. By weight, asphalt generally accounts for between 4 and 8 percent of HMA and makes up about 25 - 30 percent of the cost of an HMA pavement structure depending upon the type and quantity. The paving industry also uses asphalt emulsions, asphalt cutbacks and foamed asphalt.

“Asphalt cement" refers to asphalt that has been prepared for use in HMA and other paving applications. This section uses the generic term, "asphalt binder", to represent the principal binding agent in HMA because "asphalt binder" includes asphalt cement as well as any material added to modify the original asphalt cement properties.


Figure 1: Trinidad Lake Asphalt	Figure 2: Chevron Hawai'i Refinery

· PHYSICAL PROPERTIES OF ASPHALT

Bitumen's main property is that of a very strong and durable adhesive that binds together a very wide variety of other materials without affecting their properties. Its durability is essential to major engineering projects such as roads and waterways where it must do its job for 20 years or more.

Bitumen is insoluble in water but is soluble in numerous organic solvents. As it is highly waterproof, it can act as an effective sealant. It also resists action by most acids, alkalis and salts. It does not contaminate water so it can be used to line watercourses.

It is a thermoplastic material: it softens and becomes liquid with the application of heat and hardens as it cools. Bitumen can be spread relatively easily in the areas where it is required because it can readily be liquefied by one of three methods:

1) Applying beat

2) Dissolving it in petroleum solvents

3) Dispersing with water (emulsification).

Bitumen gives controlled flexibility to mixtures of mineral aggregates which is why so much of the total annual production is used in road building. It is available at an economic cost virtually all over the world.

Asphalt can be classified by its chemical composition and physical properties. The pavement industry typically relies on physical properties for performance characterization although an asphalt's physical properties are a direct result of its chemical composition. Typically, the most important physical properties are:

· Durability. Durability is a measure of how asphalt binder physical properties change with age (sometimes called age hardening). In general, as an asphalt binder ages, its viscosity increases and it becomes more stiff and brittle.

· Rheology. Rheology is the study of deformation and flow of matter. Deformation and flow of the asphalt binder in HMA is important in HMA pavement performance. HMA pavements that deform and flow too much may be susceptible to rutting and bleeding, while those that are too stiff may be susceptible to fatigue cracking.

Safety. Asphalt cement like most other materials, volatilizes (gives off vapor) when heated. At extremely high temperatures (well above those experienced in the manufacture and construction of HMA) asphalt cement can release enough vapor to increase the volatile concentration immediately above the asphalt cement to a point where it will ignite (flash) when exposed to a spark or open flame. This is called the flash point. For safety reasons, the flash point of asphalt cement is tested and controlled.

Purity. Asphalt cement, as used in HMA paving, should consist of almost pure bitumen. Impurities are not active cementing constituents and may be detrimental to asphalt performance.

· GRADING SYSTEM OF BITUMEN(US PROCEDURE):

Asphalt binders are typically categorized by one or more shorthand grading systems according to their physical characteristics. These systems range from simple to complex and represent an evolution in the ability to characterize asphalt binder. Today, most state agencies use or are planning to switch to the Super pave performance grading (PG) system.

· Penetration Grading:

Based on the depth a standard needle will penetrate an asphalt binder sample when placed under a 100 g load for 5 seconds (see Figure 3). The test is simple and easy to perform but it does not measure any fundamental parameter and can only characterize asphalt binder at one temperature (77°F). Penetration grades are listed as a range of penetration units (one penetration unit = 0.1 mm of penetration by the standard needle). Typical asphalt binders used in the U.S. are 65-70 pen and 85-100 pen. This system is not used in Hawai'i, although the current asphalt used would meet 805-100 pen specifications.

Figure 3: Penetration Needle

· Viscosity Grading:

Measures penetration (as in penetration grading) but also measures an asphalt binder's viscosity at 140°F and 275°F. Testing can be done on virgin (AC) or aged (AR) asphalt binder. Grades are listed in poises (cm-g-s = dyne-second/cm²) or poises divided by 10. Typical asphalt binders used in the U.S. are AC-10, AC-20, AC-30, AR-4000 and AR-8000. Viscosity grading is a better grading system but it does not test low temperature asphalt binder rheology.

· Superpave Performance Grading (PG) System:

The Superpave PG system was developed as part of the Superpave research effort to more accurately and fully characterize asphalt binders for use in HMA pavements. The PG system is based on the idea that an HMA asphalt binder’s properties should be related to the conditions under which it is used. For asphalt binders, this involves expected climatic conditions as well as aging considerations. Therefore, the PG system uses a common battery of tests (as the older penetration and viscosity grading systems do) but specifies that a particular asphalt binder must pass these tests at specific temperatures that are dependant upon the specific climatic conditions in the area of intended use. Therefore, a binder used in Hawai'i would be different than one used in, say, Alaska.

Superpave performance grading is reported using two numbers – the first being the average seven-day maximum pavement temperature (in °C) and the second being the minimum pavement design temperature likely to be experienced (in °C). Thus, a PG 64-16 is intended for use where the average seven-day maximum pavement temperature is 64°C and the expected minimum pavement temperature is -16°C. Notice that these numbers are pavement temperatures and not air temperatures. The typical PG grade used in Hawai'i is a PG 64-16. Realistically, pavement temperatures in Hawai'i will never dip down to -16°C, but the typical asphalt binder used will meet this standard so it is graded as such.

· SPECIFICATIONS OF DIFFERENT GRADES OF BITUMEN:

Sr.No.	Characteristics	80/100	60/70	30/40	10/20
1	Specific Gravity at 27 ⁰C min	0.98	0.99	0.99	1.00-1.05
2	Water percent by wt.max	0.2	0.2	0.2	-
3	Flash point, ⁰C	175	175	175	225
4	Softening point ⁰C	35-50	40-55	50-65	65-80
5	Penetration at 25 ⁰C, 100 g 5 sec in 1/100 cm	80-100	60-70	30-40	10-20
6	Ductility at 27 ⁰C, in cm. min	75	75	50	2.5
7	Loss on heating, percentage by wt.Max	1	1	1	0.10
8	Penetration of residue	60	60	60	-
9	Percent by wt. soluble in carbon di- sulphide, min	99	99	99	99

· TEST PROCEDURES:

All Test procedures Depends on

1. Characteristics

2. Test Development

3. Specifying Authorities

4. Cutback Bitumen’s

5. Bitumen Emulsions

Characteristics:

The main characteristics that bitumen must have are as follows:

Consistency: the degree of fluidity or viscosity of the bitumen at a standard temperature. As the viscosity of bitumen varies according to its temperature, when comparing grades of bitumen it is essential to carry out the tests at a standard temperature.

Safety: to ensure that bitumen may be used safely, it is essential that its flash point occurs at a much greater temperature than that at which road construction work is carried out. The flash point is the temperature at which the heated bitumen will release fumes that will ignite (flash) in the presence of a naked flame or a spark.

Test Development:

Experience in using bitumen in engineering projects has led to the adoption of certain test procedures that are indicative of the characteristics that identify adequate performance levels.

However, there are two important points to be taken into account when considering these test procedures.

First, some of the tests have evolved with the development of the industry and are empirical methods. Consequently it is essential that they are carried out in strict compliance with the recommended procedures if they are to be accurate measurements of the bitumen's properties. Modem technology is continually being employed by major bitumen manufacturers at their research centers and in industry sponsored university research projects to find new ways of measuring the physical properties of bitumen, and translating these into specifications relating to 'road performance'. Specifying Authorities Second, various organizations representing bitumen manufacturers and users have laid down standard test procedures. Major internationally used methods are:

IRC Indian Road Congress

ASTM American Society for Testing and Materials (USA)

AASHO American Association of State Highway Officials (USA)

DIN Deutsche Industrie Norm (Germany)

IP Institute of Petroleum (UK)

LCPC Laboratoire Centrale des Ponts at Chaussées (France)

SA Standards Australia (Australia)

Paving Grade Bitumens:

The test procedures used for paving grades of bitumen are as follows:

Penetration test

Viscosity

Flash Point

Ductility

Solubility

Effect of Heat and Air

Softening Point

Solubility: indicates the degree of contamination of the bitumen by other matter and therefore the presence of pure bitumen, the active adhesive or binding element. The test measures the percentage of matter that is insoluble in toluene.

Effect of heat and Air: is determined to simulate the conditions obtained when the bitumen is used to manufacture hot-mix. In the Rolling Thin Film Oven Test a movi ng film of bitumen is heated in an oven at 163°C for 60 minutes. The viscosity is measured before and after treatment. Also, the ductility is measured after treatment.

Cutback Bitumens:

For cutback bitumen’s, in addition to the viscosity and flash point tests, the following test is included in specifications:

Distillation test

Bitumen Emulsions:

Bitumen emulsions are subject to their own test procedures. Some of the tests used for determining their properties are as follows:

Consistency (Engler Viscosity test)

Water Content test

Sedimentation test

Stone Coating Ability and Water Resistance test

Particle Charge test

Sieve Residue test

Residue from Evaporation test

· USES AND MIXTURES:

1) Road Construction and Maintenance

2) Variable Factors

3) Hot Mix

4) Mixture Specifications

5) Road Recycling

6) Industrial Usage

Road Construction and Maintenance:

For many years well over 80% of world consumption of bitumen, which is estimated at 100 million tonnes, has been used for paving applications, the construction and maintenance of roads. The rest is used for various purposes. The use of bitumen in road maintenance can be up to four times its use in road construction. An understanding of how roads are built is necessary for an appreciation of the importance of the role played by bitumen. Modern road design and construction techniques are aimed at

building flexible road layers or courses so that the tensile and compressive stresses imposed by passing traffic are distributed evenly through these layers according to their relative strengths. Therefore, neither the ground supporting the road nor the individual layers are permanently deformed by these concentrated stresses.

The courses must also be made weather resistant and durable. Bitumen plays a major part in meeting this requirement because it strongly binds the aggregate particles and seals and fills

in the voids between them. its effectiveness depends on the aggregate specification, the size and number of voids and the type of bitumen. By sealing the gaps, bitumen makes it difficult

for water to penetrate the road courses and damage the natural foundation of the road. In the contact of roadbuilding, the entire road structure is called the pavement. The lowest layer of a road is the natural soil of the subgrade. For a new road it is carefully

prepared by modern machinery but for an old road this layer consists of whatever has been left by generations of traffic.

The rest of the road is made up of layers of aggregates and bitumen, each designed to do a specific job.

Aggregates is the term used to describe a mixture of hard non-metallic minerals such as crushed rock, gravel, sand and slag. Aggregates must meet engineering specifications as regards shape, strength, surface characteristics and size. The sub-base is the first layer put down by the roadbuilder and consists of compacted stone,

gravel or sand. Its function is to contribute towards the strength of the road and give the roadbuilding machinery an operating platform.

The roadbase is the main working layer of the road that gives it strength and flexibility. it is

made up of graded mineral aggregates. When roads have to carry a great deal of traffic, the roadbase mixture also contains bitumen because the load bearing performance is twice that of a non-treated granular base. The base course is a mixture of aggregates and bitumen. It adds to the strength of the road and is an even surface foundation for the top layer.

The wearing course is the top layer normally consisting of a more finely textured mixture of aggregate and bitumen. It has not only to act as a smooth running surface for the traffic but must also be as weather-proof as possible and resist the continual action of the abrasive forces imposed by the vehicles as they pass along it. The wearing course should also disperse surface water effectively to minimise the danger of skidding. Where appropriate, a tack coat of bitumen may be applied between courses to ensure adhesion of the layers. The combined depth of the bituminous layers is usually between 20 and 200 millimetres.

Variable factors:

The exact make-up of a road will depend on several variable factors such as the weight and volume of traffic it has been designed to carry, local climatic conditions and the availability of

mineral aggregates. In most cases bitumen will be needed for its properties of waterproofing and durability and as the cheapest adhesive generally available.

A minor secondary road may use bitumen only for its top two courses, at the rate of 7 tones per kilometer. A highway engineer may call for bitumen to be applied to three courses, with tack coats in between, because of the mixture's superior load bearing properties. In this case bitumen consumption can amount to 1000 tones per kilometer. The bitumen percentage in an aggregate/bitumen mixture is usually between 4-8%.

Hot Mix:

The mixing of aggregates and bitumen to produce asphalt may take place at a purpose-built plant located away from the road construction site or it may be done at the site itself. Controlled amounts of aggregates, which have been carefully graded to meet the specification, are dried and heated before being mixed with a measured quantity of hot bitumen. All this takes place in a purpose-built plant. The hot mixture, at a temperature of up

to 160°C, is carried to the construction site and laid while still hot.

This describes in simple terms a process in which skill and experience are combined with computerized control systems to carry out a complex series of operations. Various sizes of aggregates dry out gain and retain heat at different rates.

Their temperature must be controlled so that the bitumen does not cool when it is mixed with the aggregates. The supply of aggregates is continuously weighed by scales linked to the pump metering the supply of bitumen, so that a constant ratio of aggregate to bitumen is maintained. The mixing time should be no longer than is necessary for the uniform distribution of the bitumen as a coating for the aggregate particles; otherwise the bitumen film will harden as it is exposed to air. If the mixing process takes too long the durability of the mixture will be impaired. To provide consistent high quality mixtures, continuous operation of the plant is required which in turn means that all parts of the operation must be integrated so there are no hold-ups as the drying, screening, mixing, transporting and laying processes are carried out.

Bitumen supplies are ordered daily to meet the production schedules based on the road gangs' programmes for the following day. As bitumen storage capacity is usually limited, delivery has to be made on a ‘when required’ basis, often within thirty minutes of a target time based on the moment when the aggregates have been heated to the right temperature for mixing with bitumen. Any delay means that expensive fuel is wasted in keeping the aggregate

at the right temperature. This precision in delivery calls for a high degree of commitment on the part of the supplier in terms of capital equipment, logistics and technical expertise. With cutbacks and bitumen emulsions, lower aggregate (stone) temperatures (30-100°C) can be used: mixing may be carried out on site or by using mobile mixing plants. This is one of the significant advantages of using these bitumen’s when the design of the road allows them to be specified.

Mixture Specifications:

Asphalts have been classified into a number of different types, which may be simply stated as:

Asphaltic Concrete: a dense, continuously graded mixture of coarse and fine aggregates, mineral filler and bitumen produced hot in a mixing plant. It is delivered, spread and compacted while hot.

Bituminous Macadam: a road with a graded aggregate and bituminous coating, in which the mechanical interlock of the aggregate particles contributes significantly to its strength.

Open-graded Asphalt: an asphaltic mix using aggregates containing only small amounts of fine material and providing a high percentage of air voids.

Stone Mastic Asphalt: a gap-graded wearing course mix with a high proportion of coarse aggregate content which interlocks to form a stone-on stone skeleton to resist permanent deformation. The mix is filled with mastic of bitumen and filler.

Tack coat: a thin layer of emulsified or cutback bitumen that bonds a layer of road to the layer beneath. Current practice is to favour the more modem bitumen emulsions in place of cutbacks.

Surface treatments: including dressings and coats, involve spraying a coating of bitumen onto the surface of a wearing course. It can be sprayed as an emulsion, a cutback or paving grade bitumen. Either a single or double coating of fine aggregates or stone chippings is applied. These treatments are applied to renovate and waterproof old roads that require maintenance. An example of such a treatment is a fog seal which is a coat of bitumen emulsion applied to an existing surface to seal cracks as maintenance

treatment.

Bituminous Slurry Surfacing: an important maintenance treatment for the surface in which a mixture of fine aggregates and filler and emulsified bitumen is applied to a structurally sound road surface for minor shape corrections and to improve skid resistance. It has the advantage that it can be applied rapidly at a relatively low cost by a truck-mounted mixing plant.

Road Recycling:

The techniques of road recycling reclaim the materials used to build roads. They offer benefits in terms of reduced demands for aggregates and energy. The layers of road surface are ripped up, crushed and reprocessed with varying proportions of fresh aggregate, new bitumen or emulsions and, if necessary, a recycling agent. The process may be carried out on site (in situ), or the reclaimed material can be transported to and from the site to be mixed in a dedicated, static plant.

Industrial Usage:

The use of bitumen in industry accounts for less, than 20% of world bitumen production. It is nevertheless important to those manufacturers and engineers who rely on its particular properties as an economical binder and protector. In many parts of the world it is used extensively to waterproof the roofs of houses, often in the form of shingles which are strips of felt first impregnated with bitumen and then covered on both sides with harder bitumen and a

coating of mineral granules. A similar construction technique involves sheets of bitumen saturated felt laid onto a flat roof with layers of bitumen below, between and above them. In more complex roofing projects, bitumen is to be found holding in place a protective coating of chippings on the cantilevered roof of a sports stadium. By contrast, bitumen is also used in damp proofing and floor composition tiles. Other materials, particularly felts and papers, are impregnated with bitumen to improve their performance as regards insulation. Packaging papers, printing inks, linoleum, sound deadening felts hidden inside car bodies and the under sealing compounds beneath them, electrical insulating compounds and battery boxes are some of the hundreds of industrial and domestic products likely to contain bitumen.

· RATE ANALYSIS OF BITUMEN:

A) Take 1 km road, then what is the quantity of bitumen required?

B) For that first we have to know the crust details of general section of road.

C) Generally Bitumen mixes which are using for Base and Surface(Black Topping) layers are

1) B.C (Bituminous Concrete)

2) D.B.M (Dense Bitumen Macadam)

3) B.U.S.G (Built Up Spray Grout)

D) Out of this we are taking B.C for estimating the rate of Bitumen Concrete

E) Here we have to observe that we can’t find only bitumen quantity as well as bitumen rate for 1 km.

F) Instead of that we can take some particular quantity of B.C mix then we can estimate the cost of B.C only but not bitumen.

G) So we are taking 205 cumec standard quantity for calculating B.C, then we will find rate per cumec of B.C

The calculation is follows like this.

Bituminous Macadam

Providing and laying bituminous macadam with 100-120 TPH hot mix plant producing an average output of 75 tonnes per hour using crushed aggregates of specified grading premixed with bituminous binder, transported to site, laid over a previously prepared surface with paver finisher to the required grade, level and alignment and rolled as per clauses 501.6 and 501.7 to achieve the desired compaction

Unit = cum

Taking output = 205 cum (450 tonnes)

a) Labour

Mate

day

0.840

209.00

175.56

Mazdoor working with HMP, mechanical broom, paver, roller, asphalt cutter and assistance for setting out lines, levels and layout of construction

day

16.000

140.00

2240.00

Skilled mazdoor for checking line & levels

day

5.000

140.00

700.00

b) Machinery

Batch mix HMP 100-120 TPH @ 75 tonne per hour actual output

hour

6.000

17613.00

105678.00

Mechanical broom hydraulic @ 1250 sqm per hour

hour

2.200

268.00

589.60

Air compressor 250 cfm

hour

2.200

240.00

528.00

Paver finisher hydrostatic with sensor control @ 75 cum per hour

hour

6.000

2012.00

12072.00

Generator 250 KVA

hour

6.000

900.00

5400.00

Front end loader 1 cum bucket capacity

hour

6.000

607.00

3642.00

Tipper 10 tonne capacity

tonne.km

450 x L

2.00

2700.00

Add 10 per cent of cost of carriage to cover cost of loading and unloading

270.00

Smooth wheeled roller 8-10 tonnes for initial break down rolling.

hour

6.00x0.65*

346.00

1349.40

Vibratory roller 8 tonnes for intermediate rolling.

hour

6.00x0.65*

1159.00

4520.10

Finish rolling with 6-8 tonnes smooth wheeled tandem roller.

hour

6.00x0.65*

861.00

3357.90

c) Material

i) Bitumen@ 3.3 per cent of mix

tonne

14.850

23739.00

352524.15

weight of mix = 205 x 2.2 = 450 tonne

ii) Aggregate

Total weight of mix = 450 tonnes

Weight of bitumen = 14.85 tonnes

Weight of aggregate = 450 -14.85 = 435.15 tonnes

Taking density of aggregate = 1.5 ton/cum

Volume of aggregate = 290.1 cum

*Grading I ( 40 mm nominal size )

37.5 - 25 mm 15 per cent

cum

43.510

371.70

16172.72

25 - 10 mm 45 per cent

cum

130.550

389.16

50804.41

10 - 5 mm 25 per cent

cum

72.530

467.71

33922.79

5 mm and below15 per cent

cum

43.510

467.71

20349.93

GradingII(19 mm nominal size)

25 - 10 mm 40 per cent

cum

116.040

389.16

45157.75

10 - 5 mm 40 per cent

cum

116.040

467.71

54272.72

5 mm and below 20 per cent

cum

58.020

467.71

27136.36

* Any one of the alternative may be adopted as per approved design

for Grading I ( 40 mm nominal size )

d) Overhead charges @ 08 % on (a+b+c)

49359.72

e) Contractor's profit @ 10 % on (a+b+c+d)

66635.63

Cost for 205 cum = a+b+c+d+e

732991.91

Rate per cum = (a+b+c+d+e)/205 (For Grading I)

3575.57

say

3576.00

for GradingII(19 mm nominal size)

d) Overhead charges @ 08 % on (a+b+c)

49785.08

e) Contractor's profit @ 10 % on (a+b+c+d)

67209.86

Cost for 205 cum = a+b+c+d+e

739308.49

Rate per cum = (a+b+c+d+e)/205 (For Grading-II)

3606.38

say

3606.00

FLY ASH BRICKS

2012-02-25T17:29:00.000-08:00

Bitumen is defined in the Oxford English Reference Dictionary as 'a tar like mixture of hydrocarbons derived from petroleum naturally or by distillation, and used for road surfacing and roofing'.

It is widely believed that the term 'bitumen' originated in the ancient and sacred language of Hindus in India, Sanskrit, in which 'jatu' means pitch and 'jatu-krit'means pitch creating. These terms referred to the pitch produced by some resinous trees. The Latin equivalent is claimed by some originally 'gwitu-men' (pertaining to pitch) and by others to be 'pixtu-men' (bubbling pitch) which was subsequently shortened to 'bitumen' then passing via French into English.

There are several references to bitumen in the bible, although the terminology used is confusing. In Genesis, Noah's ark is "pitched within and without with pitch', and Moses' juvenile adventure is in 'an ark of bulrushes, daubed with slime and with pitch'. Even more perplexing are the descriptions of the building of the tower of Babel. The Authorised Version of the Bible says 'they had brick for stone, and slime had they for mortar'; the New International Version states that 'they used bricks instead of stone and tar instead of mortar'; Moffat's 1935 translation says 'they ha bricks for stone and asphalt for mortar'; but the New English Bible states that 'they had used bricks for stone and bitumen for mortar'. Even today, the meanings of the words bitumen, tar, asphalt and pitch vary between users.

THE EARLIEST USE OF BITUMINOUS BINDERS

Surface seepage may occur at geological faults in the vicinity of subterranean crude oil deposits. The amount and constitution of this naturally occurring material depends on a number of processes that modify the properties of the substance. This product may be considered to be a 'natural' bitumen, often being accompanied by mineral matter, the amount and nature of which will depend upon the circumstances which caused such an admixture to occur.

There are of course extensive crude oil deposits in the Middle East and for thousands of years there has been corresponding surface seepage of 'natural' bitumen. The ancient inhabitants of these parts were quick to appreciate the excellent waterproofing, adhesive and preservative properties of the material which was so readily placed at their disposal. For over 5000 years, bitumen, in one form or another, has been used as a water proofing and /or bonding agent; the earliest recorded use was by the Sumerians whose empire existed from around 3500 BC to approximately 2000BC. At Mohanjo Daro, in the Indus Valley, there is particularly well preserved water tank which dates back to around 3000 BC. In the walls of these tanks, not only are the stone blocks bonded with a natural bitumen but there is also a vertical bituminous core in the centre of the wall. This same principle is used in modern dam design. It is believed that Nebuchadnezzar was an able exponent of the use of bitumen because there is evidence that he used the product for waterproofing the masonry of his palace and as a grout for stone roads. Bituminous materials have had wide application in the building industry for a great many years. As early as 3800 B.C. they were used in construction because of their adhesive and waterproofing properties. Obtained from naturally occurring deposits these bitumens were used by the rulers of the Assyrian, Sumerian and Chaldean empires to waterproof their palace walls. The process of mummification used by the ancient Egyptians also testifies to the preservative qualities of bitumen.

The ancient uses of natural bitumen undoubtedly continued in those inhabited parts of the world where deposits were readily available. However, there seems to have been little development of usage elsewhere. In the UK, none of the present major uses of bitumen was introduced until the end of the nineteenth century. However, there would appear to have been some knowledge of alternate binders in early days as it is recorded that Sir Walter Raleigh in 1595, proclaimed the lake asphalt he founded in Trinidad to be most excellent good fir caulking ( waterproofing) the seems of ships. In the middle of the nineteenth century, attempts were made to use rock asphalt from European deposits for road surfacing and from this there was a slow development of the use of natural products for this purpose , followed by the advent of coal tar and the later of bitumen manufactured from crude oil.

In spite of the passage of many centuries, bituminous materials are still used extensively in construction; they retain their excellent adhesive and waterproofing properties although it is recognized that they can be adversely affected if the materials are improperly used. For example, under the influence of water, excessive temperature and solar radiation, bitumens can be slowly broken down to carbon dioxide and water. Their service life, however, can be greatly extended if they are given a measure of protection. It is the purpose of this Digest to discuss the properties of bituminous materials and the manner in which they should be handled to derive the maximum benefit from their use.

WHAT ARE BITUMENS?

VARIOUS DEFINATION AVAILABLE OF BITUMEN

Sci-Tech Encyclopedia: Bitumen

A term used to designate naturally occurring or pyrolytically obtained substances of dark to black color consisting almost entirely of carbon and hydrogen with very little oxygen, nitrogen, and sulfur. Bitumen may be of variable hardness and volatility, ranging from crude oil to asphaltites, and is largely soluble in carbon disulfide.

Britannica Concise Encyclopedia: bitumen

Mixture of tarlike hydrocarbons derived from petroleum. Black or brown, it varies from viscous to solid; the solid form is usually called asphalt. Bitumen occurs in nearly every part of the world and in nearly the whole range of geologic strata. The term may also refer to synthetic hydrocarbon compound.

Architecture: bitumen

A semisolid mixture of complex hydrocarbons derived from coal or petroleum, as coal-tar pitch or asphalt; before application, usually dissolved in a solvent, emulsified, or heated to a liquid state.
Columbia Encyclopedia: bitumen

(bĭtyū'mən) a generic term referring to flammable, brown or black mixtures of tarlike hydrocarbons, derived naturally or by distillation from petroleum. It can be in the form of a viscous oil to a brittle solid, including asphalt, tars, and natural mineral waxes. Substances containing bitumens are called bituminous, e.g., bituminous coal, tar, or pitch.

Occultism & Parapsychology Encyclopedia: Bitumen

Bitumen was greatly used in magical practices. Images for the purpose of sympathetic magic were often made of this sub-stance, and it was also used in ceremonies for the cleansing of houses in which any uncleanness had appeared—being spread on the floor like clay.

Veterinary Dictionary: bitumen

A series of natural and artificial dry petroleum products. When combined with pitch and used as a flooring it may contain sufficient phenol to cause poisoning in pigs fed on the floors.

Many terms and definitions of terms are used to describe bitumens. "Bitumen" itself is a generic name applied to mixtures of hydrocarbons, which can be gaseous, liquid, semi-solid or solid and are completely soluble in carbon disulphide. Within this class of materials there are many substances, the most common of which are tars, pitches and asphalts.

Tars are dark brown condensates produced by the destructive distillation of materials such as wood, peat, shale, bone and coal. Fractional distillation or partial evaporation of tar results in a solid or semi-solid residue known as pitch. Coal-tar pitch is the most common material of this type that is used in construction.

Asphalts are dark brown to black solids or semi-solids that gradually liquefy when heated. They are found in the natural state but may also be obtained from petroleum. Essentially, the origin of natural asphalt is the same as that of asphalt produced by the refining of petroleum, except that the latter process is accomplished at higher temperatures in a much shorter time.

The largest commercially exploited natural asphalt is a lake over 300 feet deep and covering an area of 100 acres on the island of Trinidad. Other natural asphalts occur as rock asphalt in Kentucky and as very hard asphalts such as Gilsonite in Utah and Colorado.

The removal of gasolines, oils and other volatile products from crude oil results in a residual asphalt often called a straight-run asphalt. The properties of this product depend upon the nature of the crude source and the conditions of refining. Residual material is often used directly, but on occasion further refining is necessary to produce a harder material. This can be achieved by an air-blowing or oxidation process in which air is blown through heated residual asphalt, control of the process producing various degrees of hardness. The actual chemical and physical process is not fully understood, owing to, the complex nature of the bituminous materials; they are thought to be colloidal and to consist of a dispersion of high molecular weight material in a fluid having a lower molecular weight. The bitumen is changed physically if this colloid system is disturbed, as may be seen when a bitumen is overheated. Some of the lower molecular weight material is distilled off so that some of the flexibility and adhesive qualities are lost. Consistency can also be increased by using pulverized mineral filler whose chief function is to increase viscosity. This achieves the same result as oxidation without sacrificing the serviceability expected from soft asphalts.

PROPERTIES OF BITUMEN

Adhesiveness of bitumen to a surface depends upon both the nature of the surface and the state of the bitumen. For an adhesive to act it must be able to wet a surface. In a fluid state bitumens can wet a dry solid surface and good adhesion will result, but the presence of water will prevent adhesion. The temperatures of the solid and the bitumen also influence the bond, as will any dust on the surface of the solid and the nature of the solid itself. Even after a bitumen bas been successfully applied, the bond can be decreased or even destroyed by the entrance of water into the bitumen-solid interface.

A number of additives to improve adhesion of bitumens to solid surfaces have been proposed. These compounds have a powerful wetting and adhesive action, and when present in small amounts in bitumens they displace water from the solid surface and permit a good bond. They also prevent any deterioration of the bond should water ever reach the interface. The creation and maintenance of a good adhesive bond between bitumen and a solid is an essential requirement for satisfactory performance.

The water resistance properties of bitumens depend upon the degree of impermeability and water absorption inherent in them. Even a very thin layer (1/64 inch) in a continuous film provides an excellent water barrier. In practical applications the degree of impermeability will be affected by the nature of the filling materials and the continuity of the bituminous coating. For waterproofing and roofing applications, fabrics or felts are used to build up a membrane to provide and maintain continuous waterproofing films.

Under certain conditions water may be absorbed by the bitumen itself or by minute quantities of inorganic salts or fillers in it. The normal solubility of water in bitumen is in the order of 0.001 to 0.01 per cent by weight and is so small as to be negligible. The presence of water soluble salts in any quantity will result in a large capacity for water absorption by osmosis. For this reason oil refineries de-salt the crude oil before refining it. Fillers also can absorb certain quantities of water, the amount varying with the composition and granular size of the material. As a result it bas been found that bitumens in permanent contact with water absorb it in varying amounts, and various claims as to the relative water absorption properties of coal-tar pitch and asphalt have been made.

Results of recent tests on asphalt and coal-tar pitch have reported water absorptions of 0.5 to 2.4 grams/sq ft for commercial coal-tar pitches and 2.0 to 3.9 grams/sq ft for commercial asphalts after one year. This rate of absorption is very low and there is very little difference between the two. It is more significant that the rate of water penetration into the bitumen is also very low.

The viscous or flow properties of bitumens are of importance, both at the high temperatures encountered in processing and application and at the low temperatures to which bitumens are subjected in service. Flow properties are complex and are further confused by changes in the colloidal nature of the bitumens that occur with heating. When the temperature is high enough for the bitumen to be liquid, the rate of shear is directly proportional to the shearing stress. As the temperature drops, how ever, these flow properties are complicated by elasticity and other effects. This has necessitated empirical tests, which. are used by the producer and consumer to measure the consistency of the bituminous materials at temperatures comparable to those encountered in the service life of the bitumen. Among the most common of these tests are the penetration and softening point tests and various indices using them.

The penetration test measures the depth of penetration in tenths of millimetres that a weighted needle achieves in a bitumen after a known time at a known temperature. The most common combination of factors is a weight of 100 grams applied for 5 seconds at a temperature of 77°F. The penetration is a measure of hardness, and typical values obtained are approximately 10 for hard coating grade asphalts, 15 to 40 for roofing asphalts, and up to 100 or more for certain waterproofing materials.

The softening point test measures the temperature in degrees Fahrenheit at which a steel ball falls a known distance through the bitumen when the test assembly is heated at a known rate. The usual combination of factors is a ¾-inch diameter steel ball weighing 3.5 grams sinking 1 inch through a 5/8-inch diameter ¼-inch thick disc of bitumen held in a brass ring, with the whole assembly heated at a rate of 9F degrees per minute. The resulting measured temperature is not the melting point, but merely gives a measure of flow under controlled conditions. The softening point value is used to grade bitumens into groups. Typical values would be up to 240°F for coating grade asphalts, from 140°F to 220°F for roofing asphalts, and down to approximately 115°F for certain waterproofing materials.

When chilled sufficiently all bitumens lose their viscous properties and behave as brittle elastic solids. The interval between the softening point temperature and the temperature at which a brittle condition is reached gives a measure of the temperature susceptibility of the material. This can vary a great deal, depending on the crude oil source and the bitumen processing. Successful use of bitumen usually results if a material has been chosen that will be subjected in service to temperatures well within the limits defined by its brittle condition and softening point.

Lack of compatibility between different bitumens is also of importance, and exhibits itself by staining and the appearance of oil spots or large cracks. If a coal-tar pitch and an asphalt are incompatible, one will be softened and the other hardened, the nature and extent of incompatibility depending upon the chemical composition and internal physical structure of the bitumens. The reaction of asphalt towards pitch can be manifested in two ways:

1. If asphalt is applied over pitch it can soften and flow off, leaving exposed pitch that will weather rapidly.

2. If pitch is applied over asphalt, the pitch may harden and crack.

These reactions do not always occur and sometimes asphalt can be applied over pitch, or vice versa, with no ill effects. It is considered advisable, however, to avoid contact of the two bitumens if possible, and for this reason asphalt should not be used with tar-saturated felt, nor should tar be used with asphalt-saturated felt. If any doubt exists on the compatibility of bituminous materials, a test bas been devised to establish it (ASTM D1370-58).

To enable bitumens to wet the surface that is to be protected, they are often applied in the hot liquid state. The temperature to which they should be heated depends upon both the consistency of the bitumen and the temperature of the surface to, which it is applied. As a maximum temperature exists, however, above which chemical degradation of the bitumen occurs, it is not advisable to, heat asphalts above 450°F and coal-tar pitches above 400°F. Coal-tar pitches and one grade of asphalt for built-up roofing have a softening point of about 140°F; it is thus possible, by heating these materials even to 350°F or lower, to obtain a liquid that will wet a dry solid surface and enable the bitumen to be applied so that it can act as a waterproofing agent.

It is occasionally desirable to avoid the use of a hot material. At such times bituminous products are used in so-called cold applications, with the bitumen in liquid form as a cutback or an emulsion. (A cutback material is a solution of the bitumen in a suitable solvent.) After application of the bituminous solution to the solid surface, the solvent evaporates leaving the bituminous film to act as a coating. Numerous solvents are sufficiently volatile and are good solvents for bitumens, but many are either too expensive or too hazardous. To control the drying times of the solution, care must be taken in the selection of the bitumen and solvent.

Emulsions are dispersions of very small drops of bitumen in water. A satisfactory emulsion is smooth in appearance, usually brown In colour, and can be made from bitumens having a wide range of consistencies. Emulsions usually contain a mineral material and are often called clay emulsions, although the mineral can also be coal, shale, metallic oxides, portland cement or asbestos. The most widely used is a special clay known as bentonite. An obvious advantage of emulsions over other bituminous products is that they are easy to handle, addition of water being all that is necessary to decrease their viscosity. Curing involves, primarily, a loss of water by evaporation; its stability, however, depends upon many factors such as asphalt concentration, size and distribution of asphalt droplets, freezing of the water and the nature of the stabilizing agent.

DURABILITY OF BITUMEN

Mention bas been made of the changes that bitumens undergo when they are overheated; this is but one of the peculiarities encountered in their handling and service. Among the other factors to be considered are water absorption and photo-oxidation. Bitumens are readily oxidized when subjected to ultra-violet radiation, a process that forms water soluble products and results in a material that is harder and less flexible than it was originally. If it continues until the bitumen can no longer withstand the strains imposed by thermal and structural movement, the material cracks. The loss of volatile materials also causes contractions that frequently cause shrinkage cracks. In the absence of light and heat, however, the rate of oxidation is low and the useful life of the materials can be extended. Light-coloured gravel in built-up roofing construction provides the protection required for satisfactory durability.

GENERAL USES OF BITUMENS

Bitumen is primarily used for paving roads. Its other uses are for general waterproofing products, including the use of bitumen in the production of roofing felt and for sealing flat roofs. It is also the prime feed stock for petroleum production from tar sands currently under development in Alberta, Canada. Bitumen from tar sands is projected to account for 80% of Canadian oil production by 2020.

In the past, bitumen was used to waterproof boats, and even as a coating for buildings. The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon. It is also possible that the city of Carthage was easily burnt due to extensive use of bitumen in construction.

Vessels for the heating of bitumen or bituminous compounds are usually excluded from public liability insurance policies.

Most geologists believe that naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae and other once-living things. These organisms died and their remains were deposited in the mud on the bottom of the ocean or lake where they lived. Under the heat and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum. Bitumens are found also in meteorites, archean rocks, copper, zinc mineralizations, and caves. It is possible that bitumens are primordial material formed during accretion of the earth and reworked by bacteria that consume hydrocarbons.

Bitumen was also used in early photography technology. It was most notably used by French scientist Joseph Nicephore Nipce in the first picture ever taken. The bitumen used in his experiments were smeared on pweter plates and then exposed to light thus making a black and white image.

USES OF BITUMENS AS WATER PROOFING

The desirable qualities of bitumens control the uses to which they may be put; the limitations of the materials control the methods of application and their performance in service. Adhesiveness and waterproofing qualities, combined with low cost, make them useful as a protective agent in both built-up and prepared roofing and in prepared siding. They have wide use also as sealants and adhesives. Combined with other materials, bitumens may be used as vapour barriers and as agents to waterproof and damp-proof structures.

Bitumen is used in many forms depending upon the characteristics and properties desired. Saturated felts, used in built-up roofing as a base for prepared roofing and siding, as underlays for floors, and as a membrane for waterproofing, require a particular grade of bitumen that bas a low viscosity at the saturation temperature. The flash-point should be above the saturating temperature, however, and a reasonably low temperature susceptibility is desirable. In the preparation of asphalt-saturated felt an asphalt having a softening point of approximately 140°F and penetration value of 50 is used.

Prepared roofing products such as shingles and roll roofing consist of saturated felts coated with asphalt. The coating grade asphalts used for this application are high softening point (200 to 240°F) air-blown products with high penetration values of 18 to 30 at 77°F; they have low temperatures susceptibility. Care is taken during manufacture to ensure that the coating asphalt is compatible with the saturant.

Bitumens are widely used to provide a waterproof coating to walls and to construct waterproof membranes in buildings and engineering structures. Hot applied bitumens used below grade, where they are not subjected to high temperatures, are of a type having a low softening point (115 to 145°F) and a high penetration value (up to 85). Where the bitumen is to be used above grade and may be applied to vertical surfaces exposed to direct solar radiation, a type having a higher softening point (200 to 220°F) and a lower penetration value (15 to 25) should be selected. Emulsions and cutbacks that are applied cold are being used to an ever-increasing extent for damp-proofing and waterproofing. They may be used alone or with felts to build up a membrane.

Asphaltic cutbacks and emulsions have their greatest use in road construction and maintenance. With roofing it accounts for about 95 per cent of the asphalt produced in North America. There are still, however, large quantities of asphalt modified by the addition of mineral matter used in the building industry as sealants, acoustical coatings and paints.

SPECIFICATION FOR MODIFIED BITUMINOUS SHEET WATERPROOFING

PART 1 ‑ GENERAL

1.1 DESCRIPTION:

This section specifies modified bituminous sheet material used for exterior below grade waterproofing and split slab waterproofing.

1.2 MANUFACTURER'S QUALIFICATIONS:

A. Approval by Contracting Officer is required of products and services of proposed manufacturers, and installers, and will be based upon submission by Contractor that:

1. Manufacturer regularly and presently manufactures bituminous sheet waterproofing as one of its principal products.

2. Installer has technical qualifications, experience, trained personnel and facilities to install specified items.

3. Manufacturer's product submitted has been in satisfactory and efficient operation on three similar installations for at least three years.

4. Submit list of installations, include name and location of project and name of owner.

1.3 SUBMITTALS:

A. Submit in accordance with Section 01 33 23, SHOP DRAWINGS, PRODUCT DATA, AND SAMPLES.

B. Manufacturer's Literature and Data:

1. Bituminous sheet.

2. Primer.

3. Mastic.

4. Protection material, temporary and permanent.

5. Printed installation instructions for conditions specified.

C. Certificates:

1. Indicating bituminous sheet manufacturer's approval of primer, and roof cement.

2. Indicating bituminous sheet waterproofing manufacturer's qualifications as specified.

3. Approval of installer by bituminous sheet manufacturers.

4. Water test report.

1.4 PRODUCT DELIVERY, STORAGE AND HANDLING:

A. Deliver materials to job in manufacturer's original unopened container.

B. Do not store material in areas where temperature is lower than 10 degrees C (50 degrees F,) or where prolonged temperature is above 32 degrees C (90 degrees F).

1.5 ENVIRONMENTAL REQUIREMENTS:

Ambient Surface and Material Temperature: Not less than 4 degrees C (40 degrees F), during application of waterproofing.

1.6 warranty:

Warrant bituminous sheet waterproofing installation against moisture leaks and subject to terms of "Warranty of Construction", FAR clause 52.246-21, except that warranty period is two years.

1.7 APPLICABLE PUBLICATIONS:

A. Publications listed below form a part of this specification to the extent referenced. Publications are referenced by basic designation only.

B. Federal Specifications (Fed. Spec.):

UU‑B‑790A............... Building Paper, Vegetable Fiber: (Kraft, Water‑

INT AMD 1 Proof, Water Repellent and Fire Resistant)

C. American Society for Testing and Materials (ASTM):

C578-07..................... Rigid Cellular Polystyrene Thermal Insulation

D41-05....................... Asphalt Primer Used in Roofing, Dampproofing and Waterproofing

D2822-05................... Asphalt Roof Cement

D6380-03................... Asphalt Roll Roofing (Organic Felt)

D. American Hardboard Association (AHA):

A135.4-1995.............. Basic Hardboard

PART 2 ‑ PRODUCTS

2.1 BITUMINOUS SHEET:

A. Cold applied waterproofing membrane composed primarily of modified bituminous material prefabricated in sheet form designed for below grade exterior and split slab waterproofing. Sheet reinforced with fibers at manufacturer's option.

B. Thickness of Bituminous Sheet: 1.5 mm (60 mils), plus or minus 0.13 mm (5 mils), and bonded to a 0.1 mm (4 mil) thick plastic sheet.

C. Provide with a release sheet to prevent bonding of bituminous sheet to itself.

2.2 PRIMER AND ROOF CEMENT:

A. Furnished by manufacturer of bituminous sheet as required for particular application in accordance with sheet manufacturer's instructions.

B. Primer: ASTM D41.

C. Roof Cement: ASTM D4586.

2.3 PROTECTION MATERIAL:

A. Polystyrene: ASTM C578, Type I or VIII, 13 mm (1/2-inch) minimum thickness.

B. Hardboard: PS-58, Service Type, 6 mm (1/4‑inch) thick.

C. Waterproofed Building Paper: Fed. Spec. UU-B-790.

D. Roll Roofing: ASTM D6380, Class S (smooth), Type III with minimum net mass per unit area of roofing, 2495 g/m² (51 lb/100 ft²).

2.4 PATCHING COMPOUND:

A factory prepared, non‑shrinking, fast setting, cementitious adhesive compound containing no ferrous metal or oxide.

PART 3 ‑ EXECUTION

3.1 PREPARATION:

A. Surface Condition:

1. Before applying waterproofing materials, ensure concrete and masonry surfaces are fully cured, smooth, clean, dry, and free from high spots, depressions, loose and foreign particles and other deterrents to adhesion.

2. Fill voids, joints, and cracks with patching compound.

B. Concrete surfaces cured a minimum of seven days, free from release agents, concrete curing agents, and other contaminates.

3.2 APPLICATION:

A. Priming:

1. Prime concrete and masonry surfaces.

2. Application method, amount of primer and condition or primer before installation of bituminous sheet as recommended by primer manufacturer.

3. Reprime when required in accordance with manufacturer's instructions.

B. Bituminous Sheet Installation:

1. Remove release sheet prior to application.

2. Lay bituminous sheet from low point to high point so that laps shed water.

3. Treat expansion, construction and control joints and evident working cracks as expansion joints. Apply bituminous sheet in double thickness over joint by first applying a strip of bituminous sheet not less than 200 mm (8 inches) wide, centered over joint.

4. Lap seams not less than 50 mm (2 inches).

5. Lay succeeding sheet with laps, and roll or press into place.

6. Repair misaligned or inadequately lapped seams in accordance with manufacturer's instructions.

7. Seal seams and terminations in accordance with sheet manufacturer's instructions.

C. Corner Treatment:

1. At inside and outside corners apply double cover using an initial strip not less than 280 mm (11 inches) wide, centered along axis of corner.

2. Cover each strip completely by the regular application of bituminous sheet.

3. Provide a fillet or cant on inside corners.

4. Form cants using patching compound

5. Do not use wood, fiber, and insulating materials for cants.

D. Projection Treatment:

1. Apply a double layer of bituminous sheet around pipes and similar projections at least 150 mm (6 inches) wide.

2. At drains, apply a bead of roof cement over a double layer of bituminous sheet under clamping rings.

3.3 PROTECTION:

A. Protect bituminous sheet before backfill or wearing courses are placed.

B. Install protection material and hold in place in accordance with instructions of manufacturer of waterproofing materials.

C. Permanent Protection:

1. Vertical Surfaces:

a. Install hardboard, polystyrene, or roll roofing protection material.

b. Extend protection full height from footing to top of backfill.

c. If graded backfill is used, use roll roofing or hardboard.

D. Horizontal Surfaces:

1. Install roll roofing protection under concrete wearing courses.

2. Install roll roofing, hardboard, or polystyrene under earth backfill.

3. Where no concrete wearing course occurs or when surfaces will bear heavy traffic and will not immediately be covered with a wearing course, use protection specified for vertical surfaces.

E. Temporary Protection:

When waterproofing materials are subjected to damage by sunlight and can not be immediately protected as specified, protect waterproofing materials by waterproof building paper or suitable coating approved by manufacturer of waterproofing system used.

3.4 PATCHING:

Repair tears, punctures, air blisters, and inadequately lapped seams, in accordance with manufacturer's instructions before protection course is applied.

3.5 TESTING:

A. Before any protection or wearing course is applied, test all horizontal applications of waterproofing with a minimum of 25 mm (1-inch) head of water above highest point and leave for 24 hours.

B. Mark leaks and repair when waterproofing is dry.

C. Certify, to Resident Engineer, that water tests have been made and that areas tested were found watertight.

3.6 INSPECTION:

Do not cover waterproofed surfaces by other materials or backfill until work is approved by Resident Engineer.

ALTERNATIVES OF BITUMEN

The world has become increasingly concerned over the global climate change thought to be caused by greenhouse gases, chief among them anthropogenic carbon dioxide which is released into the atmosphere from burning fossil fuels. This has led to the introduction of bitumen alternatives that are more environmentally friendly and non toxic. Bitumen can now be made from non-petroleum based renewable resources such as sugar, molasses and rice, corn and potato starches. Bitumen can also be made from waste material by fractional distillation of used motor oils, which is sometimes disposed by burning or dumping into land fills.

Non-petroleum based bitumen binders can be made light-colored. Roads made with lighter-colored pitch absorb less heat from solar radiation, and become less hot than darker surfaces, reducing their contribution to the urban heat island effect.

SUMMARY

Some of the more important properties of bitumens have been examined in this Digest. Particular mention has been made of the adhesive, waterproofing and flow characteristics that control the use to which bitumens are placed in construction. An outline has also been given of the various bitumens and the manner in which they are used. Recent studies have produced much information to justify even more research into the properties of bituminous materials. As more becomes available on composition, internal structure, mechanisms of flow, degradation and adhesiveness, a more widespread and even more successful use of this material in construction can be anticipate

WATERPROOFING OF BUILDINGS

2012-02-25T16:56:00.000-08:00

Waterproof or water-resistant describes objects unaffected by water or resisting water passage, or which are covered with a material that resists or does not allow water passage. Such items may be used in wet environments or under water. Waterproofing describes making an object waterproof or water-resistant.

Waterproofing is a method by which an item is made resistant to damage by water. Waterproofing is the formation of an impervious barrier which is designed to prevent water entering or escaping from various sections of building structures. Internal areas that are waterproofed include bathrooms, shower recesses, laundries and toilets. Whilst an External area waterproofed extends to roofs, planter boxes, podiums, balconies, retaining walls and swimming pools.

Waterproofing is the combination of materials or systems that prevent water intrusion into structural elements of the buildings or its finished spaces. Basic waterproofing and envelope design incorporates 3 steps to ensure a watertight and environmentally sound interior :

1. Understanding water sources likely to be encountered

2. Designing systems to prevent leakage from these sources.

3. Finalizing the design by properly detailing each individual envelope component into adjacent components.

CAUSES OF LEAKAGE

For leakage to occur, 3 conditions must be present

· Water in any of its forms must be present.

· Water must be moved along by some type of force, including wind, gravity for above-grade envelope components and hydrostatic pressure or capillary action for below-grade components.

· Finally and the most important, there must be a breach (hole, brak, or some type of opening) in the envelope to facilitate the entry of water into the protected spaces

Available water is moved into the interior of a structure by numerous forces that include:

· Natural gravity

· Surface tension

· Wind/Air currents

· Capillary action

· Hydrostatic pressure

The first 3 typically are encountered on above-grade portions of the envelope, whereas the last 2 are recognized at grade or below-grade areas of buildings or structures

WATERPROOFING IN CONSTRUCTION

In construction, a building or structure is waterproofed with the use of membranes to protect contents underneath or within as well as protecting structural integrity. The waterproofing of the building envelope in construction specifications is under '07 - Thermal and Moisture' protection and includes roofing material as well as waterproofing materials.

A building or structure needs waterproofing as concrete itself will not be watertight on its own. The conventional system of waterproofing involves 'membranes'. This relies on the application of one or more layers of membrane (available in various materials: e.g., bitumen, silicate, PVC, HDPE, etc.) that act as a barrier between the water and the building structure, preventing the passage of water. However, the membrane system relies on exacting application, presenting difficulties. Problems with application or adherence to the substrate can lead to leakage.

Over the past two decades, the construction industry has had technological advances in waterproofing materials, including integral waterproofing systems as well as more advanced membrane materials.

Integral systems work within the matrix of a concrete structure, giving the concrete itself a waterproof quality. There are two main types of integral waterproofing systems: the hydrophilic and the hydrophobic systems. A hydrophilic system typically uses a crystallization technology that replaces the water in the concrete with insoluble crystals. Various brands available in the market claim similar properties, but not all can react with a wide range of cement hydration by-products, and thus require caution. Hydrophobic systems use fatty acids to block pores within the concrete, preventing water passage.

New membrane materials include

Hydrotech’s Monolithic Membrane 6125 (MM6125) and

Re-New’s Turbo Seal.

These new materials seek to overcome shortcomings in older methods like PVC and HDPE. Generally, new technology in waterproof membranes relies on polymer based materials that are extremely adhesive to create a seamless barrier around the outside of a structure.

If we bifurcate a structure in to different categories with respect to waterproofing perhaps we can classify the structure in to following: -

1. Waterproofing of foundations

2. Waterproofing of basements

3. Waterproofing of bathrooms and toilets,

4. Waterproofing of terraces

Waterproofing of the above mentioned areas needs a detailed site investigation in case of old construction but in new construction if the proper methodology and proper materials are used the structure can be made waterproof for period of five years extended to twenty years depending on the materials used for waterproofing. In this project, we will try to understand different techniques used to waterproof foundations and basements only but before that we will try to understand what are the methods used in waterproofing any part of structure with the help of an flowchart.

DAMPNESS AND ITS EFFECTS

A wet cellar can dramatically reduce the value of your home. Studies show that most people won't even consider buying a home with water leakage. Selling a home with water leaks can easily result in as much as a 25% reduction in the sale price.

Even if you rarely have problems with dampness or flooding, it's best to solve the problem completely before doing any remodeling work. Permanent solutions can take time to implement. A good place to start is to talk to an independent home inspector who specializes in waterproofing problems.

Proper insulation is critical to creating a comfortable, dry basement. Besides keeping out the cold, basement insulation prevents condensation. The ground stays cool year round. It in turn keeps basement walls cool. When the warmer air in the room comes in contact with all those cool walls, it has to give up some of its moisture in the form of condensation. In fact, condensation is the primary source of the moisture that causes mold and mildew problems in basements. Effective insulation separates the warm air of the room from the cool walls, thereby preventing the moisture problems that stem from condensation. (see below the top-10 most common insulation mistakes in basements)

1. DEFECTS CAUSED BY DAMPNESS:-

The various defects caused by dampness in buildings may be summarized as under:

1. It causes efflorescence which may ultimately result in disintegration of bricks, stone, tiles, etc.

2. It may result in softening and crumbling of plaster.

3. It may cause bleaching and flaking of paint with the information of colored patches.

4. It may result in warping, buckling and rotting of timber.

5. It may lead to corrosion of metal

6. It may deteriorate electrical fittings.

7. It promotes growth of termites.

8. It breeds mosquitoes and creates unhealthy living conditions for the occupants.

2. CAUSES OF DAMPNESS

Absorption of moisture by the building materials is one of the chief cause of dampness. On account of granular nature of materials, moisture finds an easy access through the voids and this aided by capillary action assists the moisture to travel in different directions. Thus, either on account of faulty design of structure or bad workmanship or by use of defective materials, moisture may find its way to interior of the building either through the foundation and plinth, walls, chhajjas, floors or the roof.

3. SOURCES OF DAMPNESS

The important sources of dampness may be summarized as below:-

1. Dampness rising through the foundation walling. Moisture from wet ground may rise well above ground level on account of capillary action.

2. Splashing rain water which rebounds after hitting the wall surface may also cause dampness.

3. Penetration of rain-water through unprotected tops of walls, parapets, compound walls etc. may cause dampness.

4. In case of slope roofs rain-water may percolates through defective roof covering. In addition, faulty eaves course and eaves or valley gutter may allow the rain-water to descend through the top of supporting wall and cause dampness.

5. On condensation, the moisture present in the atmosphere gets deposited on the components of the building which may cause dampness.

6. In case of flats roofs, inadequate roof slopes, improper rain-water pipe connections and defective junction between roof slab and parapet wall may prove to be the sources of dampness.

Dampness caused due to leakages in wet areas of a building which include kitchen, bathroom, water closet etc. The leakages could be on account of use of sub-standard plumbing fittings and fixtures as well as faulty execution of work and bad work-man ship.

4. SURFACE TREATMENT

The moisture finds its way through the pores of materials used in finishing. In order to check the entry of the moisture into the pores, they must be filled up. Surface treatment consists in filling up the pores of the surface subjected to dampness. The use of water repellent metallic soaps such as calcium and aluminum oleates and stearates is much effective in protecting the building against the ravages of heavy rain. Bituminous solution, cement coating, transparent coating, paints and varnishes fall under this category. In addition to other surface treatments given to walls, the commonly used is lime cement plaster. The wall plaster with cement, lime and sand mixed in proportion of 1:1:6 are found to serve the purpose of preventing dampness in wall due to rain effectively.

5. MATERIAL USED FOR WATER PROOFING

An effective damp proofing material should have the following properties:

1. It should be impervious.

2. It should be strong and durable be capable of withstanding both dead as well as live loads without damage.

3. It should be dimensionally stable.

4. It should be free from deliquescent salts like sulphates, chlorides and nitrates.

The material commonly used to check dampness can be divided into the following four categories:

1. Flexible material:- material like bitumen felts ( which may be Hessian –base or fibre/glass fibre-based) , plastic sheeting ( polythene sheet) etc.

2. Semi-rigid material: - Material like mastic asphalt or combination of material or layers.

3. Rigid material:- Material like first class bricks, stones, slates, cement concrete etc.

4. Grout consisting of cement slurry and acrylic based chemicals/polymers.

6. SIGNS THAT YOU HAVE WATERPROOFING PROBLEMS IN YOUR BASEMENT

Mold and Mildew
Fungus that grows in damp and dark areas, and cause discoloration, or musty odors.

Moldy Odors
This is the result of the decay process from mold, and dry rot.

Peeling Paint
Peeling paint is a sign that you have moisture problems and waterproofing issues.

Damp Spots on Walls
Water has absorbed through your walls.

White Substance on Basement Walls
This is a chemical breakdown of the bonding agent that holds your walls together. This white substance is a sign of possible structural deterioration.

Cracked Walls
Should be inspected to determine the exact cause.

Rust on Appliances or Furniture
Like furnaces. Rust is caused by a wet environment and is the sign of waterproofing issues.

Dry Rot
Black fungus grows mostly on walls or wooden surfaces, causing wood to decay.

Basement Waterproofing

Water may enter a basement through various means including through joints, walls, or floors. Various basement waterproofing systems address these problems. There are many systems available of varying cost, effectiveness, and installation invasiveness.

We shall now discuss few methods of waterproofing basements.

7. WATER PROOFING TREATMENT BY USING GROUT CONSISTING OF CEMENT MORTAR ADMIXED WITH ACRYLIC BASED CHEMICALS ALONG WITH ROUGH STONE SLABS:-

This treatment is presently being commonly adopted for ensuring water tightness of basement in damp soil or at site where sub soil water table is high. The treatment consists in enclosing the entire basement with in a water proof box constructed by use of rough stone slabs and cement mortar admixed with acrylic based chemical.

The steps are as followed:-

Step 1:- The excavation of the ground for the basement is carried out in such a way that a working space of at least 750 mm is available around the periphery of the external walls of the proposed basement. The excavated area is kept dry by continuous pumping using well-point equipment or by adopting any other suitable method. Over the dry leveled ground a 75 to 100 mm thick layer of lean concrete 1:3:6 is laid to serve as mud mat or leveling course for the raft slab. This layer of lean concrete should project by 150 mm beyond the external wall. Over the layer of lean concrete a layer of 15 to 20 mm thick rough quarry-finished stone slabs is laid over 20 mm thick cement mortar (1:4) admixed with acrylic based chemical. The stone slabs are laid side by side leaving a gap of about 15 to 20 mm between them. The joints thus left are raked open and ground with cement slurry admixed with acrylic based chemical. A 20 mm thick layer of cement mortar (1:4) admixed with acrylic based compound is laid over the stone slabs stone chips 12 mm & down are embedded at random in this layer of mortar.

The total maximum thickness of the above water proofing layer should be around 6 60 mm. This layer should cover the entire area of lean concrete i.e. it should be extended 150 mm beyond the external face of raft slab/walls.

Step 2:- The R.C.C. raft slab suitably designed to with stand the highest applicable water pressure during monsoon is laid over the water proofing layer in step 1. The R.C.C. walls of the basement are constructed monolithically with the R.C.C. raft. After the curing of the R.C.C. wall is over, the water proofing treatment is continued unbroken on the external sides of the walls, so as to form an external box of the water proofing level.

Step 3:- To continue the treatment along the vertical plane, a groove about 30 to 40 mm deep is made in top mortar layer or bottom layer of the water proofing treatment [laid in step (1) ]at a clear distance of about 18 mm from the external face of the wall all along the periphery of the basement. Rough quarry-finished stone slabs 15 mm to 20 mm in thickness are fixed vertically in the above groove.

The stone slabs are fixed side by side without leaving any gap between the edges. Maximum of two to three horizontal layers of stone are laid at a time one over the other vertically up. A coat of very rough cement plaster (1:4) is applied to the external face of the rough stones. After the layer is set, the gap between the wall and stone layer is filled with a grout made up of cement slurry admixed with acrylic based chemical, which on gellation forms an impermeable layer, monolithic with the external face of the wall.

A final coat of 15 mm cement mortar plaster (1:4) is applied over the rough external cement plaster and finished smoothly. This treatment to external face of walls is continued up to 300 mm above ground level. The acrylic based chemical is normally added @ 1 % i.e. 1 kg of chemical to be mixed with 100kg of cement.

8. WATERPROOFING USING FLEXIBLE PVC WATERBARS

Description: - Waterbars are flexible PVC water stops to seal construction and expansion joints in concrete structures.

Uses: - Waterbars are used in concrete for the sealing of construction and expansion joints. It is installed in a specified position, allowing concrete to be poured around it. The material takes up it’s function as a joint sealant once the concrete has hardened and a joint has been formed. Depending on the type of Waterbar, it can be used for construction or expansion joints.

Advantages: -

· Multi-rib sections provide a tortuous path and impenetrable water check.

· Easy to fix using tie-clips (See below photo)

· Easy on-site welding.

· High strength PVC material.

Specifications: - Waterbars comply with: U.S. Corporation of Engineers Specification. CRD-C572-74. Requirements of BS2571 and BS2782.

Application: -

SURFACE WATERBARS: Installed into the face of the concrete structure. The waterbar is typically fixed on the water side of the concrete wall or floor, by attaching it temporarily to the formwork using fixing wire. The protruding ribs become cast into the concrete to provide an excellent watertight seal as well as securely anchoring the waterbar to the structure.

INTERNAL WATERBARS: The waterbar is fitted into split formwork or shuttering for casting centrally into the concrete. Use fixing wire or tie-clips to attach waterbar to internal reinforcement.

WELDING: Waterbars are made from thermoplastic PVC and cantherefore be welded. The ends are heated with on-site welding equipment until the PVC becomes plastic and is then immediately pressed together. Waterbars allow easy on-site welding, including the prefabrication of cross, T, L and corner pieces.

Profiles: -

Centerstop: - Centrally placed Waterbars O type section is used in expansion, contraction and construction joints. The bulb in the centre allows for movement in the structure to be accommodated for. The waterstops are easily anchored to the steel reinforcement using special tie-clips.

Rearguard Construction: - The externally placed rearguard Waterbars AR sections are used in construction and contraction joints. The centrally placed fin assists with shutter locations.

Rearguard Expansion: - The externally placed rearguard Waterbars DR sections are designed with a flat top box section, with a protruding fin, to assist with positioning and to provide a chair to support the joint filler. The section is used in expansion joints to accommodate movement.

Intersection: - A wide range of standard intersection pieces are available. All have a minimum 200mm free leg, allowing easy butt-welding on site. For nonstandard types, drawings must be provided, giving exact details of angles and length of legs. Standard intersection pieces include: X, T and L pieces both flat and on edge.

Technical Data: -

Basis : Polyvinyl Chloride

Colour : Yellow

Density : 1.3kg/litre

Service Temperature : -35°C to 55°C

Hydrostatic Head : Up to 60 metres

Joint Movement : Up to 10 mm (expansion joint

profiles only)

Tensile Strength (ASTM-D412-75) : longitudinal > 13 N/mm² transverse

> 12.5² N/mm²

Elongation at Break (ASTM-D412-75) : longitudinal > 310% transverse >

260%

Alkali Resistance (CRD-C572-65) : Passed

Important: - Good placement practice must be followed to ensure that concrete is well placed and compacted around the Waterbar during installation. In the case of factory made junctions, where angles are not 90°C, drawing must be provided giving exact joint details. Other profile types and widths are available upon request (depending on volume).

9. WATERPROOFING USING LIQUID APPLIED CEMENTITIOUS MEMBRANE

Description: - Liquid Applied Cementitious Membrane is the materials which are available in two components and sometimes three components depending on the manufacturer. The two components consist of Liquid and Powder. The Liquid is a mixture of polymers and water, these polymers acts as strength providing material when mixed with Powder which is generally a cement based material. Is a high performance two component flexible acrylic polymers modified cement based waterproof coating for concrete and masonry surfaces. The system consists of a powder and a liquid, is grey in colour and easily applied by brush.

Features and Benefits: -

· Provides excellent impermeable coating

· Heavy duty waterproof coating

· Good adhesion with cementitious surfaces

· Applied for Positive & negative sides of waterproofing

· Easily Brush applied

· Flexible enough to take care of minor cracks in concrete & plaster

· Durable & economical

· Non-flammable

· Application tools easily washed in water

· Available in pre-packed, ready-to-use containers

Method of Application: -

· The RCC walls and the base slab of basement must be cured for 28 days minimum before applying liquid applied cementitious membrane. The condition of walls and base slab must be assessed carefully for any irregularities and cavities. All the cold joints must be inspected for its water tightness. If required, inject cement slurry admixed with expansive grouts should be injected into the cold joints.

· Prepare the surface carefully to receive the first coat of the material. All the loose particles and debris must be removed with the help of wire brush. The grouting holes must be finished to level and ensure that they are properly sealed with suitable material.

· The entire area must be thoroughly wetted with water to a state where it is saturated. But extra care must be taken to see that there is no stagnant or standing water. Any such water must be mopped off. As such, the concrete substrate to receive the treatment must be in a Saturated Surface Dry Condition.

· Mix both the parts i.e. Liquid and Powder with a slow speed (100 - 150 RPM) forced action mixer for big quantity of 15 kg, to achieve an even consistency.

· All the powder lumps formed during mixed must be hand crushed completely. PLEASE DO NOT ADD WATER during mixing. For large application areas, take up a quantity that can be mixed and applied in 20 - 30 minutes.

· ALWAYS ADD the POWDER component into the LIQUID and NOT the LIQUID into the powder.

· Over the properly pre-wetted surface, apply first coat at a thickness of 500-600 microns and allow it dry for 5-6 hours. Apply the 2 coats at the same thickness. The total applied thickness should be of minimum 1.5 mm in three coats.

· Allow each coat to dry sufficiently before applying next coat.

· Allow Dr. Fixit Pidifin 2K film to air cure for atleast 72 hours.

Precautions and Limitations: -

· Must be protected from foot traffic & other physical abuse

· Do not pond with water immediately after the 2nd coat. Allow it air to cure for atleast 72 hours

· Pre-wetting of the substrate is essential before coating

· Film thickness of 1 to 1.2 mm must be achieved in 2 coats. For a critical areas 1.5 mm thick film is recommended to be achieved in 3 coats

· Must be applied on totally cured surface

· Do not undertake application in hot sun (above 300C) and below 100C

· Do not dilute product with water at site.

10. WATERPROOFING OF BASEMENTS USING TORCH – ON MEMBRANES

These membranes are perhaps the best for waterproofing of terraces having large spans, also when the concept of terrace garden or roof swimming pools is used. It is entirely a bituminous product and requires a primer and the membrane for application on to the surface. The membrane is slightly melted with the heat which is shown in the pictures and thus the best waterproofing can be achieved for atleast 25 years. The finished membrane is over coated with a paint of aluminum to give heat proofing.

Primer application: -

Apply solvent-based bitumen primer on cleaned & leveled surface @ 3-5 sq.mtr/ltr. The priming will enhance the adhesion of the membrane to the substrate. Allow the primer coat to dry. The drying will generally depend on the ambient temperature.

Membrane Application

Starting from one end, unroll the TORCHSHIELD roll once the priming coat is dried. Align the TORCHSHIELD roll correctly & re-roll it half in alignment before torching. Avoid shifting of the membrane while torching Use gas burner to heat substrate & underside to softening points. When the embossing disappears, roll forward & press firmly against substrate. Ensure sufficient bleed on side & end over laps. Once the half of the roll is torched properly to the substrate, unroll the balance roll and repeat the process. An overlap of 100-mm shall be maintained for all the continuing sides. Heating shall be done on both the membranes to be overlapped and pressed firmly with the help of round shape trowel. The care shall be taken to leave no gap at any point in the overlapped area. If noticed, reheating shall be done to seal it. The Torchshield must be laid over the entire PCC area with a minimum of 150 mm over hang from the size of raft on all sides.

Protection

The Torchshield membranes shall be protected against damage by laying sand cement mortar in 1:4 ratio at 15 to 20 mm thickness. Cure the surface for 7 days before starting the work for laying RCC raft or column footings.

Method of Application

The entire external surface of the wall shall be prepared properly and made ready to receive the waterproofing treatment. All the honeycomb areas, undulations, cracks shall be filled with polymer modified mortar. For which Dr. Fixit Polymer Mortar PX shall be used as per the standard material specification.

Primer Application

Bitumen based primer shall be applied as explained above over the entire surface and shall be allowed to dry.

Membrane Application

Torchshield shall be applied as per the standard installation practices as explained above over the dried primer. Before the application of Torchshield begins over the wall, a corner rounding / angle fillet shall be made at the junction of PCC and Raft to avoid the right angle bend of membrane.
The application of membrane shall begin from the edge of PCC with a sufficient lap of 100 mm minimum with the bottom membrane (over PCC) and to be taken over raft thickness and then over the wall. An overlapping of 100 mm must be ensured with the subsequent membrane with all sides. The fixing shall be done from the PCC level moving horizontally first and then vertically. All the lap joints and termination shall be done as per standard specifications as explained earlier.


Clean & remove dust, dirt, loose particles and unsound substrate	Apply primer coat with solvent based bitumen primer	Unroll the TORCHSHIELD roll


Align the Torchshield Roll	Use gas burner to heat substrate & underside to softening points	Keep overlap margin for minimum 100 mm


Heat both the overlaps & use round tipped trowel to seal overlap	Seal the edges well and protect with a Polysulphide sealant	Torchshield applied all over the terrace

Protection

The back filling can start simultaneously as one move upward. Before back filling begins, the membrane shall be protected either with plaster or with a protection board.
For plaster, sand shall be sprinkled over the membranes as soon as it is fixed after torching. The plastering shall be done in 1:3 sand cement mortar at 15 mm thickness. Thermocol in 20 mm thickness can be used as a protection board. The cold bitumen (mastic) can be used for fixing the Thermocol over the Torchshield. Once the Thermocol is fixed, back filling can start in layers. This will allow people to work comfortably as it will create the platform to work as one move upwards.

11. WATERPROOFING USING CRYSTALLIZATION

Crystallization is the (natural or artificial) process of formation of solid crystals precipitating from a uniform solution or melt, or more rarely deposited directly from a gas. Crystallization is also a chemical solid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.

Process: -

The crystallization process consists of two major events, nucleation and crystal growth. Nucleation is the step where the solute molecules dispersed in the solvent start to gather into clusters, on the nanometer scale (elevating solute concentration in a small region), that becomes stable under the current operating conditions. These stable clusters constitute the nuclei. However when the clusters are not stable, they redissolve. Therefore, the clusters need to reach a critical size in order to become stable nuclei. Such critical size is dictated by the operating conditions (temperature, supersaturation, etc.). It is at the stage of nucleation that the atoms arrange in a defined and periodic manner that defines the crystal structure — note that "crystal structure" is a special term that refers to the relative arrangement of the atoms, not the macroscopic properties of the crystal (size and shape), although those are a result of the internal crystal structure.

The crystal growth is the subsequent growth of the nuclei that succeed in achieving the critical cluster size. Nucleation and growth continue to occur simultaneously while the supersaturation exists. Supersaturation is the driving force of the crystallization, hence the rate of nucleation and growth is driven by the existing supersaturation in the solution. Depending upon the conditions, either nucleation or growth may be predominant over the other, and as a result, crystals with different sizes and shapes are obtained (control of crystal size and shape constitutes one of the main challenges in industrial manufacturing, such as for pharmaceuticals). Once the supersaturation is exhausted, the solid-liquid system reaches equilibrium and the crystallization is complete, unless the operating conditions are modified from equilibrium so as to supersaturate the solution again.

Many compounds have the ability to crystallize with different crystal structures, a phenomenon called polymorphism. Each polymorph is in fact a different thermodynamic solid state and crystal polymorphs of the same compound exhibit different physical properties, such as dissolution rate, shape (angles between facets and facet growth rates), melting point, etc. For this reason, polymorphism is of major importance in industrial manufacture of crystalline products.

Description: -

It is a unique chemical treatment for the waterproofing and protection of concrete that is suitable for the following applications:

· Foundation walls

· Basement walls

· Manholes

· Parking decks

· Reservoirs

· Sewage and water treatment tanks

· Tunnels

· Underground vaults

It can be used on either poured-in-place concrete or concrete block and can be applied to either the interior or exterior surface with equal results.

Characteristics: -

It waterproofs underground structures from the inside against hydrostatic pressure. By the process of diffusion and the materials have an affinity with water, the crystalline formation migrates throughout the pores and capillary tracts of concrete even against strong hydrostatic pressure. When mixed with water and applied as a cementitious coating, the active chemicals cause a catalytic reaction which generates a nonsoluble crystalline formation of dendritic fibers within the pores and capillary tracts of concrete. Thus, the concrete itself becomes permanently sealed against the penetration of water or liquids from any direction.

It protects concrete and reinforcing steel. This treatment is highly resistant to most aggressive substances, pH 3 - 11 constant contact and pH 2 - 12 periodic contact. By preventing the intrusion of chemicals, salt water, sewage and other harmful materials, It protects concrete and reinforcing steel from deterioration and oxidation. The concrete is also protected against spalling, efflorescence, popouts and other damages caused by weathering, bleeding of the salts and internal expansion and contraction during the freeze/thaw cycle.

Crystallization permits concrete to breathe. The crystalline formation has fixed-size air spaces so small that water cannot pass through. It does allow the passage of air and vapor; thus the concrete is able to breathe and become thoroughly dry, preventing moisture vapor buildup. These products are nontoxic. They have been approved by NSF International (National Sanitation Foundation), U.S. Environmental Protection Agency, Agriculture Canada and many other governmental health agencies throughout the world for use on concrete structures that hold potable water or are in contact with foodstuffs.

Advantages: -

· Not just a surface coating – Not dependent upon continuity of membrane for waterproofing action.

· Seals hairline cracks upto 0.4 mm.

· No surface priming or leveling required.

· Cannot puncture, tear or come apart at the seams.

· Does not require protection during backfilling or during placement of steel, wire mesh or other materials.

· Can be applied to moist or green concrete

· Less costly to apply than most other waterproofing methods.

Types: -

Crystalline waterproofing technology is available in 3 forms:

· As a coating – For new or existing structures.

· As a dry shake material – For new horizontal surfaces.

· As an admixture – Included in the concrete mix at the time of batching.

Concentrate: -

Used as a single coating on above- or below grade concrete, or as the first of a 2-coat application where 2 coats are required. Also used as a Dry-Pac for sealing construction joints and for repair of cracks, faulty construction joints and honeycombing. Concentrate is the most chemically potent of the crystalline waterproofing materials.

Modified: -

Used as a second coat to reinforce Concentrate where 2-coats are required and as a single coat for exterior damp proofing.

Concentrate DS1 and DS2: -

Dry shake formulations designed for application on fresh horizontal concrete prior to finishing operations.

Admix: -

Used as an integral waterproofing admixture which is included in the concrete mix at the time of batching.

Patch’n Plug: -

Fast-setting, nonshrink, high bond strength hydraulic cement compound for concrete repairs. Stops flowing water in seconds. Patch’n Plug seals cracks and tie holes. It is also used for the general repair or patching of concrete. Patch’n Plug can be used in conjunction with Admix to increase the compressive strength and bond strength of existing concrete.

Acrylic Admix: -

An acrylic polymer formulation specifically designed for use as an admix to fortify Portland cement mixes. Acrylic Admix increases hardness, durability, bonding capability and chemical resistance.

Gamma-Cure: -

Can be used as an alternative to water curing for certain applications.

Installation

Surface Preparation: -

· Concrete surfaces to be treated must be clean and free of laitance, dirt, films, paint, coatings or other foreign matter.

· Surfaces must also have an open capillary system so as to provide tooth and suction for treatment. If surfaces are too smooth, the concrete should be acid etched, lightly sandblasted or water blasted.

· Structural defects such as cracks, faulty construction joints and honeycombing should be routed out to sound concrete and repaired.

· Horizontal surfaces should have a rough wood float or broom finish. On fresh horizontal concrete Concentrate DS1 or DS2 powder can be power troweled into the surface while it is still in plastic state.

Wetting Concrete: -

Prior to the application, concrete surfaces must be thoroughly wetted with clean water to control surface suction, aid the proper curing of the treatment and ensure the growth of the crystalline formation deep within the pores of the concrete. Excess surface water should be removed before the application.

Methods: -

To mix the product for slurry coat application, the Xypex powder is mixed with clean water to a creamy consistency in the following proportions by volume:

Mixing for Brush Application: -

· Mix 5 parts powder to 2 parts of water (0.8 kg/m²).

· Mix 3 parts powder to 1 part of water (1.0 kg/m²).

Mixing for Spray Application: -

· Mix 5 parts powder to 3 parts water (0.8 kg/m²). The mix may vary with equipment type.

Mixing for Dry – Pac: -

· Mix 6 parts Concentrate powder with 1 part clean water by volume. Do not mix too wet, other wise, mix may crack and spall at it dries.

Application: -

The treatment should be applied with a semi-stiff bristle brush, a janitor’s broom for large horizontal applications, or with specialized spray equipment. The treatment must be uniformly applied under the conditions and quantities specified. One coat should have a thickness of 1/16" (1.6 mm). When a second coat is required, it should be applied after the first coat has reached an initial set but is still green (less than 48 hours). Light pre-watering between coats may be required due to drying. The treatment cannot be applied in rain or during freezing conditions.

Spray Application of Crystalline

Brush Application of Crystalline

Curing: -

· A misty for spray of water must be used for curing the treatment.

· Curing must begin as soon as the coating has hardened sufficiently so that it is not damaged by a fine spray.

· Under most conditions, it is sufficient to spray the material treated surfaces 3 times a day for 2 – 3 days.

· In hot, dry weather, spraying may be required more frequently.

· During the curing period, the treatment must be protected from rainfall, frost and puddling of water.

WATERPROOFING MATERIALS

1. PIDIPROOF LW (Specifications conforms to IS-2645) - Its an Integral liquid waterproofing compound for plaster and concrete.

Features / Benefits

· Being a liquid, dispersible in concrete/mortar mixes.

· Makes concrete/mortar more cohesive

· Increases durability, by increase in impermeability.

· Economical in application

· Does not affect the setting time and strength.

· Reduces shrinkage cracks in plaster and concrete

· Shelf life : 1 year

Typical applications

For waterproofing of concrete and sand-cement mortar used in basements, roof slabs and screeds, water retaining structures, external plastering,

Technical information

· Base : Fatty acid

· Total solid content : 13+0.5%

· pH : High alkali

Dosage/Coverage

200 ml per 50 kg bag of cement. Just add gauging water that is to be mixed with mortar/concrete.

2. TONIC (Cement additive)

Features / Benefits

· Delays corrosion by minimising chloride penetration

· Increases workability for easy placement.

· Increases strength and durability, by reducing water cement ratio.

· Produces waterproof concrete/mortar by blocking capillaries/pores in the concrete

· Shelf life : 1 year

Typical applications

Dr. Fixit TONIC shall be added to all types of concrete and mortar to achieve water proof and durable concrete/mortar e.g. RCC column, beam, slab, water retaining structures, external plastering, screeds, water tanks, sumps and drains, etc.

Technical information

· Base : Polymer modified Fatty acid

· Total solid content : 13.50+0.5%

· Specific gravity: 1.05+0.02

· pH : High alkali

Dosage/Coverage

200 ml per 50 kg bag of cement. Just add to gauging water that is to be mixed with mortar/concrete.

3. PIDIFIN 2K(Certification by CFTRI, Mysore, for Portable water contact) – It is brush applied waterproofing coating for balconies, small terraces, wet areas & ledges

Features / Benefits

· Provides excellent impermeable coating.

· Good adhesion with cementaitious surfaces

· Applied for positive & negative sides of waterproofing

· Flexible enough to take care of minor cracks in concrete & plaster.

· Durable and economical

· Available in pre-packed, ready-to-use containers.

· Shelf life : 6 months

Typical applications

· Bathrooms and wet areas

· Small terraces upto 1000 sq.ft.

· Internal walls for prevention from seepage due to rain lash

· Small water tanks interior surfaces (upto 30,000 ltrs. capacity)

Technical information

· Appearance : Grey powder + white liquid

· Mix ratio (Powder:Liquid) = 2:1(by weight)

1.5:1(by volume)

· Pot life at 30 degree Celsius : Approx. 30 mins.

· Application temp : Between 10-30 degree Celsius

Dosage/Coverage

6-7 sq.ft./kg for 2 coats for total minimum thickness of 1 mm approximately. For protection against physical damage, a mortar screed of 15-25 mm thickness may be provided.

4. PIDICRETE URP(SBR Latex for waterproofing and repairs)

Features / Benefits

· White liquid, easily brush applied.

· Useful as waterproofing coat.

· Useful as a bonding agent between old and new concrete surfaces.

· Excellent as a cement modifier.

· Repair mortar modified with Dr.FIXIT Pidicrete URP suitable for repairing of RCC beams, columns, slabs and other RCC members

· Shelf life : 1 year

Typical applications

· Waterproofing of terraces, toilets, edge, masonary walls, sloping RCC roofs etc.

· Repairs to RCC members

· Waterproofing mortars/concretes.

· As an additive in plasters at 5-6% by weight of cement content

Technical information

· Total active solid content: 34+2%

· pH : 8-9

· Pot life : 30-45 minutes, when mixed with cement at 30 degree celsius

Dosage/Coverage

20-22 sq.ft./kg for 2 coats(URP + cement in proportion 1:1.5)

5. SUPER LATEX (SBR Latex for waterproofing and repairs)

Features / Benefits

· Excellent coverage 70-80 sq.ft./kg in 2 coats, hence economical

· Less material wastage: material does not fall back/rebound, when used as bonding agent.

· High bond strength.

· Prevents leakage and dampness.

· Enhances strength of a repair mortar & provides durability.

· Shelf life : 1 year

Typical applications

· As a bond coat : Plaster to plaster, Concrete to concrete, for plaster over brick masonry.

· As waterproof repair plaster.

· Crack repair : Plaster cracks more than 5mm in gaps developed between masonry and RCC members

· As coating for prevention of corrosion in rebars.

· Efflorescence(salt petre/damp surfaces)

Technical information

· Type : Styrene butadiene rubber polymer liquid

· Colour : white

· Storage condition : free from frost

· Active solid content : 44+1%

Dosage/Coverage

Mix (S.Latex:Water:Cement) = 1:4:7, 70-80 sq.ft./kg for 2 coats as a waterproof coating.

PRESTRESSING METHOD IN MULTI-STORIED BUILDING FRAME

2012-02-19T21:13:00.000-08:00

History of Pre-stressing

The art of pre-stressing concrete evolved over many decades and from many sources, but we can point to a few select instances in history that brought about this technology.

In the United States, engineer John Roebling established a factory in 1841 for making rope out of iron wire, which he initially sold to replace the hempen rope used for hoisting cars over the portage railway in central Pennsylvania. Later, Roebling used wire ropes as suspension cables for bridges, and he developed the technique for spinning the cables in place.

During the 19th century, low-cost production of iron and steel, when added to the invention of portland cement in 1824, led to the development of reinforced concrete. In 1867, Joseph Monier, a French gardener, patented a method of strengthening thin concrete flowerpots by embedding iron wire mesh into the concrete. Monier later applied his ideas to patents for buildings and bridges.

Swiss engineer Robert Maillart’s use of reinforced concrete, beginning in 1901, effected a revolution in structural art. Maillart, all of whose main bridges are located in Switzerland , was the first designer to break completely with the masonry tradition by putting concrete into forms technically appropriate to its properties – yet visually surprising. His radical use of reinforced concrete revolutionized masonry arch bridge design.

The idea of pre-stressing concrete was first applied by Eugene Freyssinet, a French structural and civil engineer, in 1928 as a method for overcoming concrete’s natural weakness in tension. Pre-stressed concrete can now be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforced concrete.

PRE-STRESSED CONCRETE

Pre stressed concrete, like reinforced concrete, is a composite material which uses to advantage the compressive strength of concrete, whilst circumventing its weakness in tension. Pre stressed concrete is made from structural concrete, usually of high strength, and high strength steel tendons which may or may not be grouped together. Prior to external loading the tendons are tensioned in one of two ways. With pretensioning the tendon are tensioned prior to the casting of the concrete and using post tensioning techniques the tendons are tensioned after the concrete has hardened. Some ordinary reinforcing steel is also often included both as subsidiary longitudinal reinforcement and as transverse stirrups to resist shear.

Pre-stressed concrete is a method for overcoming concrete's natural weakness in tension. It can be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforced concrete. Pre-stressing tendons (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a compressive stress that offsets the tensile stress that the concrete compression member would otherwise experience due to a bending load. Traditional reinforced concrete is based on the use of steel reinforcement bars, inside poured concrete. The basic purpose of pre-stressing is to improve the performance of concrete members and this is achieved by inducing in the beam initial deformation and stresses which tend to counteract those produced by the service loads.

Since concrete is weak in tension in normal reinforced concrete construction cracks develop in the tension zone at working loads and therefore all concrete in tension is ignored in design.

Pre-stressing involves inducing compressive stresses in the zone, which will tend to become tensile under external loads. This compressive stress neutralizes the tensile stress so that no resultant tension exists, (or only very small values, within the tensile strength of the concrete). Cracking is therefore eliminated under working load and all of the concrete may be assumed effective in carrying load. Therefore lighter sections may be used to carry a given bending moment, and pre-stressed concrete may be used for longer span than reinforced concrete.

The pre-stressing force also reduces the magnitude of the principal tensile stress in the web so that thin-webbed I - sections may be used without the risk of diagonal tension failures and with further savings in self-weight.

The pre-stressing force has to be produced by a high tensile steel, and it is necessary to use high quality concrete to resist the higher compressive stresses that are developed. As the name itself suggests pre-stressing is the technique of stressing a structural member prior to loading to resist excessive tensile stresses.

The advantages of pre-stressed concrete as a construction material in multi storied frame can be listed as follows:

· Maximum utilization of provided section of the member.

· Provision of slender member for long span beams as compared to RCC.

· Use of high strength materials contribute to the durability of the structure.

· Pre-stresses concrete has considerable resilience and impact resistance.

· Proves to be economical only in long span beam-column frames compared to other materials.

· The intermediate distance between the columns can be in increased by using pre-stressed concrete as compared to reinforced cement concrete.

· Architectural design provisions and specifications can be achieved using pre-stressed concrete.

· Dead weight of concrete is reduced to a higher rate using pre-stressed concrete.

PRINCIPLE OF PRESTRESSING

The function of pre-stressing is to place the concrete structure under compression in those regions where load causes tensile stress. Tension caused by the load will first have to cancel the compression induced by the pre-stressing before it can crack the concrete.

Pre-stressing can be applied to concrete members in two ways, by pre-tensioning or post-tensioning. In pre-tensioned members the pre-stressing strands are tensioned against restraining bulkheads before the concrete is cast. After the concrete has been placed, allowed to harden and attain sufficient strength, the strands are released and their force is transferred to the concrete member. Pre-stressing by post-tensioning involves installing and stressing pre-stressing strand or bar tendons only after the concrete has been placed, hardened and attained a minimum compressive strength for that transfer.

METHODS AND SYSTEM OF PRE-STRESSING

There are two methods of pre-stressing concrete: -

1) Pre-cast Pre-tensioned

2) Pre-cast Post-tensioned

Both methods involve tensioning cables inside a concrete beam and then anchoring the stressed cables to the concrete.

Pre-cast Pre-tensioned: -

Pre-tensioning is a method of pre-stressing in which the steel tendons are tensioned before the casting of the member. In this method the tendons are tensioned using hydraulic jacks, which bear on strong abutments between which the moulds are placed. After the concrete attains full strength the tendons are released and the stress is transferred to the concrete by bond action.

Procedure of precast pre-tensioned concreting

Stage 1

Tendons and reinforcement are positioned in the beam mould.

Stage 2
Tendons are stressed to about 70% of their ultimate strength.

Stage 3
Concrete is cast into the beam mould and allowed to cure to the required initial strength.

Stage 4
When the concrete has cured the stressing force is released and the tendons anchor themselves in the concrete.

Pre-cast Post-tensioned: -

Post-tensioning is a method of pre-stressing in which the steel tendons are tensioned after the casting of the member. In this method ducts or sheaths are placed in the required profile in the mould and the tendons are passed through the ducts. After the concrete had attained sufficient strength the tendons are tensioned using hydraulic jacks which bear on the member itself. The stress is transferred to the concrete by bearing action of tendons which are anchored using suitable anchorages. Finally the ducts are grouted and the anchor plates concealed by cement mortar.

Procedure of precast post-tensioned concreting

Stage 1
Cable ducts and reinforcement are positioned in the beam mould. The ducts are usually raised towards the neutral axis at the ends to reduce the eccentricity of the stressing force.

Stage 2
Concrete is cast into the beam mould and allowed to cure to the required initial strength.

Stage 3
Tendons are threaded through the cable ducts and tensioned to about 70% of their ultimate strength.

Stage 4

Wedges are inserted into the end anchorages and the tensioning force on the tendons is released. Grout is then pumped into the ducts to protect the tendons.

TYPES OF POST TENSIONED CONCRETING METHODS

1. BONDED POST-TENSIONED CONCRETE METHOD

2. UNBONDED POST-TENSIONED CONCRETE METHOD

BONDED POST-TENSIONED CONCRETE

Bonded post-tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and the curing process (in situ). The concrete is cast around a plastic, steel or aluminium curved duct, to follow the area where otherwise tension would occur in the concrete element. A set of tendons are fished through the duct and the concrete is poured. Once the concrete has hardened, the tendons are tensioned by hydraulic jacks that react against the concrete member itself. When the tendons have stretched sufficiently, according to the design specifications, they are wedged in position and maintain tension after the jacks are removed, transferring pressure to the concrete. The duct is then grouted to protect the tendons from corrosion. This method is commonly used to create monolithic slabs for house construction in locations where expansive soils (such as adobe clay) create problems for the typical perimeter foundation. All stresses from seasonal expansion and contraction of the underlying soil are taken into the entire tensioned slab, which supports the building without significant flexure. Post-stressing is also used in the construction of various bridges, both after concrete is cured after support by falsework and by the assembly of prefabricated sections, as in the bridge. The advantages of this system over unbonded post-tensioning are.

1. Large reduction in traditional reinforcement requirements as tendons cannot destress in accidents.

2. Tendons can be easily 'weaved' allowing a more efficient design approach.

3. Higher ultimate strength due to bond generated between the strand and concrete.

4. No long term issues with maintaining the integrity of the anchor/dead end.

UNBONDED POST-TENSIONED CONCRETE

Unbonded post-tensioned concrete differs from bonded post-tensioning by providing each individual cable permanent freedom of movement relative to the concrete. To achieve this, each individual tendon is coated with a grease (generally lithium based) and covered by a plastic sheathing formed in an extrusion process. The transfer of tension to the concrete is achieved by the steel cable acting against steel anchors embedded in the perimeter of the slab. The main disadvantage over bonded post-tensioning is the fact that a cable can destress itself and burst out of the slab if damaged (such as during repair on the slab). The advantages of this system over bonded post-tensioning are:

1. The ability to individually adjust cables based on poor field conditions (For example: shifting a group of 4 cables around an opening by placing 2 to either side).

2. The procedure of post-stress grouting is eliminated.

3. The ability to de-stress the tendons before attempting repair work.

Picture number one shows rolls of post-tensioning (PT) cables with the holding end anchors displayed. The holding end anchors are fastened to rebar placed above and below the cable and buried in the concrete locking that end. Pictures numbered two, three and four shows a series of black pulling end anchors from the rear along the floor edge form. Rebar is placed above and below the cable both in front and behind the face of the pulling end anchor. The above and below placement of the rebar can be seen in picture number three and the placement of the rebar in front and behind can be seen in picture number four. The blue cable seen in picture number four is electrical conduit. Picture number five shows the plastic sheathing stripped from the ends of the post-tensioning cables before placement through the pulling end anchors. Picture number six shows the post-tensioning cables in place for concrete pouring. The plastic sheathing has been removed from the end of the cable and the cable has been pushed through the black pulling end anchor attached to the inside of the concrete floor side form. The greased cable can be seen protruding from the concrete floor side form. Pictures seven and eight show the post-tensioning cables protruding from the poured concrete floor. After the concrete floor has been poured and has set for about a week, the cable ends will be pulled with a hydraulic jack, shown in picture number nine, until it is stretched to achieve the specified tension.

The advantages of post-tensioning compared to pre-tensioning in the multi storied frame construction can be listed as follows

a) Tendons can be provided in any desired profile.

b) Stage pre-stressing can be adopted conveniently.

c) Costly factory equipments are not required.

d) Cast-in-situ construction procedure can be conveniently adopted.

e) It is possible to fabricate a beam with pre-cast and cast-in-situ elements, which are post-tensioned together to form a single structural unit.

f) Number of systems is available in this method.

Systems of pre-stressing are as given below

· Hoyer system – usually adopted for pre-tensioned members.

The system listed below are adopted for post-tensioning

· Freyssinet system

· Magnel Balton system

· Gifford Udall system

· PSC monowire system

· CLL standard system

· Lee -Macall system

ADVANTAGES OF PRECAST CONCRETE ELEMENTS IN BUILDING CONSTRUCTION

· Lower construction cost

· Thinner slabs, which are especially important in high-rise buildings where floor thickness savings can translate into additional floors for the same or lower cost

· Fewer joints since the distance that can be spanned by post-tensioned slabs exceeds that of reinforced construction with the same thickness

· Longer span lengths increase the usable unencumbered floorspace in buildings and parking structures

· Fewer joints lead to lower maintenance costs over the design life of the structure, since joints are the major locus of weakness in concrete buildings.

· One-stop shopping sources much of a building's shell in one efficient, precast contract.

· Fabrication of precast elements during permitting and/or site preparation saves time resulting in fast efficient construction regardless of weather conditions.

· Designing precast systems is easier.

· Precast components can be erected in winter conditions, maintaining tight schedules.

· With total precast systems, speedy erection allows the contractor to enclose the building quickly, giving interior trades faster access.

· Precast components are naturally fire protected, because they will not burn. Precast's inherent fire resistance eliminates the messy and time-consuming fireproofing required for a steel structure and subsequent repairs caused by other trades.

LOSS OF PRESTRESS

When the tensioning force is released and the tendons are anchored to the concrete a series of effects result in a loss of stress in the tendons. The effects are :

· Relaxation of the steel tendons

· Elastic deformation of the concrete

· Shrinkage and creep of the concrete

· Slip or movement of the tendons at the anchorages during anchoring

· Other causes in special circumstances, such as when steam curing is used with pre-tensioning.

Total losses in pre-stress can amount to about 30% of the initial tensioning stress.

Freyssinet system is the most widely adopted system in the construction of pre-stressed concrete structures. Pre-stressed Concrete is an architectural and structural material possessing great strength. The unique characteristics of pre-stressed concrete allow predetermined, engineering stresses to be placed in members to counteract stresses that occur when the unit is subjected to service loads. This is accomplished by combining the best properties of two quality materials: high strength concrete for compression and high tensile strength steel strands for tension.

REASONS FOR USING PRESTRESSED CONCRETE

Column-Free Long Spans

With fewer columns and more usable floor space, precast, prestressed concrete provides greater freedom for space utilization.

Conserves Energy

Pre-stressed concrete components can improve the thermal storage potential of a building. It effectively conserves energy required for heating and cooling.

Maintenance Free

Precast concrete does not require painting and is free from corrosion. Its durability extends building life.

Resists Fire

Durability and fire resistance mean low insurance premiums and greater personnel safety. Those who investigate life cycle costing will appreciate the precast concrete's excellent fire resistance characteristics.

Rapid Construction

Precast concrete construction gets the job done sooner. The manufacturing of prestressed members and site preparation can proceed simultaneously. Early occupancy provides obvious benefits to the client.

Versatility of Design

Precast concrete buildings are not only functional but beautiful as well. Numerous panel configuration design possibilities are available.

Sustainability
As with all concrete wall systems, precast offers high durability and strength as well as thermal mass, which contributes to increased energy efficiency. Precast systems use locally derived materials, and can incorporate recycled supplementary cementitious materials like fly ash and slag cement, one of the key reasons why they are often used in sustainable or “green” buildings.

Variety, Flexibility, Utility

One of the biggest benefits of precast systems is in their design: tight controls mean more efficient mix designs, resulting in smaller structural members and longer spans. Construction waste is reduced because the exact amount of necessary components is delivered to the site; any spare components can be recycled, and their materials used again in another structure. Precast systems can adopt almost any aesthetic, incorporating a variety of colours and textures, or emulating natural stone. By crafting systems that not only look great, but also act as structural walls and support floor loads, designers can reduce material redundancy—and project costs.

Quality in Manufacturing

Because components are precast at manufacturing facilities, quality control measures ensure that every piece is made to specifications. The components can be cast and transported to the job site while designs are still being finalized, helping to speed construction schedules. Evolutions in self-consolidating concrete also promise to offer new options and challenges for designers using precast.

Applications

Prestressed concrete is the predominating material for floors in high-rise buildings and concrete chambers in nuclear reactors, as well as in columns and shear walls in the buildings intended for a high degree of earthquake and blast protection.

Unbonded post-tensioning tendons are commonly used in parking garages as barrier cable. Also, due to its ability to be stressed and then de-stressed, it can be used to temporarily repair a damaged building by holding up a damaged wall or floor until permanent repairs can be made.

GENERAL PRECAUTIONS IN PRESTRESSED CONCRETING

Working platforms

To provide a safe working environment, working platforms need adequate working space, appropriate edge protection, and safe access and egress.

They must also be designed and constructed to safely support all expected loads, including impact loads. Factors that will determine the selection of an appropriate working platform include:

· The type and number of items of stressing equipment that may be in use,

· The number of people required, or likely to be, on the work platform at any one time, and the likely material storage on the platform.

The platform should be large enough to enable the operators to remain clear of anchorages during stressing, and it should be at a height which eliminates or minimises risk of injury from over-reaching or awkward postures.

Formwork
In the case of cast in-situ concrete constructions, working platforms may be built integrally with the formwork.

Formwork and propping systems should be designed by a structural engineer experienced in formwork design.

Assembled formwork and propping systems should be checked by a competent person for compliance with the formwork design drawings and documented proof of such on-site checks should be readily available.

Provisions for stressing

Anchorages for stressing should be set out and tendon spacing marked on the ends. Since the wedging forces at anchorages are high, anti-burst provisions, such as special reinforcement, need to be installed and secured into position.

Pre-stressing ducts should be laid in accordance with the specified profile and adequately secured. Inadequate cover to duct tubes can result in concrete blow-outs during grouting operations.

Pre-stressing safety considerations

Stressing operations and associated preparations for stressing involve a variety of tasks which if, appropriate precautions are taken, could endanger the health and safety of workers carrying them out and/or those in the vicinity.

· The area where preparations and stressing are intended to take place must be fully barricaded with solid panels and signage prominently posted to keep unauthorised personnel clear of this area.

· All personnel involved in the tasks should wear the personal protective equipment. This will generally include safety goggles, gloves, sturdy protective footwear and safety helmets.

· All personnel involved in the tasks should have adequate training in identifying the hazards of stressing and their associated risks.

Uncoiling, Cutting and Placing Strands

· Coils are very heavy, typically weighing 3 to 4 tonnes, and therefore the structural adequacy of the area where coils are to be placed must be verified. Manual handling issues associated with handling the coils should be controlled.

· Ensure that the coils are restrained with uncut restraining straps when placing them onto the strand frame. Uncontrolled release of the coil can result in whip-back with sufficiently high force to cause serious injury.

· Strands should not be cut by heat-type cutting equipment such as oxy-acetylene or LP gas torches, as this may compromise their load-bearing capacity under tension.

· When assembling tendons, thoroughly inspect each individual wire or strand for obvious flaws.

Pushing Strands into Ducts

· All strands for each of the tendons should be pushed into place in accordance with the drawings, making sure all personnel are kept clear of the direct line of ducting to prevent injury from strands exiting from the other end of the duct.

· Once the specified number of strands is in place, ensure that a "dead end" is created for each strand by securing them at the end of the element.

· In strand set-ups where ends will protrude above the face of the concrete element and may create a hazard, they should be boxed or barricaded to prevent injury.

Concrete Pour
Concreting may be placed with either pumps or kibbles.

When concreting is being pumped, "chairs" or other means to support concrete pump lines above the reinforcement and tendons should be in place and well secured.

Where kibbles are used to place concrete, avoid dropping concrete in one place as tendons could be displaced. Concrete should always be allowed to flow in a controlled manner.

During concrete pouring:

· Ensure that the ducts and strands are not damaged during the pour. All damage should be promptly notified to the contractor's supervisor for repair. However, concrete around the anchorages needs adequate vibration to ensure a safe and sound seating for the anchorage.

· Concrete test cylinders should be taken at agreed intervals for storing and curing on site under conditions similar to those applying to the element being poured.

Stressing operationsBefore stressing operations.

Prior to commencing stressing operations, the post-tensioning supervisor should verify that:

· Concrete around the anchorages has been examined. The principal contractor should be notified if the concrete is of poor quality.

· All concrete test cylinders have achieved the specified strength.

· The grips in the jacks on the stressing equipment are clean and free from dirt or grit and in good condition.

· The stressing equipment, i.e. jacks and their gauges, has appropriate service records and up-to-date calibration certificates. All jacks should have a durable tag securely attached which clearly shows the following information:

o Final stressing pressure

o Diameter and grade of the strand for which the jack is being used

o Jack number

o Corresponding gauge number

o Date calibration expires

· The operator of the stressing equipment has documented evidence of appropriate training.

· A "NO GO" area of at least 2 metres radius is in place around the anchorages at the dead and live ends, with barricades behind the line of jacks and "Stressing in Progress. Keep Clear" signage prominently displayed at all appropriate locations

During stressing operations

· Tendons should be stressed in order from the furthest to the closest reachable to ensure that no person is standing in direct line of the jack or previously stressed strands.

· Ensure stress is applied gradually and evenly to tendons.

· Ensure that the specified initial and final stressing levels are not exceeded.

After stressing operations

· Gain the design engineer's approval prior to cutting off excess tendons.

· Seal anchorage recesses following approval and prior to grouting the ducts.

· Do not perform tasks requiring impact, such as hammering, drilling or coring in the vicinity until the grouting of the ducts has been completed.

Grouting
Build-up of excessive pressure during grouting can result in "blow-outs" of the concrete, which could injure personnel in the vicinity.

To prevent blowouts

· Ducts should be blown through to ensure there are no blockages.

· Avoid non-continuous grouting to ensure no blockages or voids are in the tubes.

· Monitor the gauge of the equipment throughout grouting to ensure that excessive pressure does not develop.

· Retain barricades used during stressing operations and also barricade at a lower level if formwork has already been removed.

NEW MATERIALS IN CONSTRUCTION (CONCRETE)

2012-02-19T20:38:00.000-08:00

The development and application of new materials in construction continually adds to the choices and decisions facing clients, designers and all responsible for building and construction. They continually seek greater and more reliable information about the serviceability in order that they meet more stringent design, safety and economic criteria.

Ever since Thomas Edison patented portland cement in 1907, it has been used for a variety of different uses. Sidewalks, buildings, sinks, and furniture are but a few of the products made from cement in the form of concrete. Cement is the dry powder that when mixed with other additives and water makes concrete. Over the past decade, new types of concrete and cement have been formulated that do everything from bend, to grow plants, and let light through.

In 2005, researchers at the University of Michigan created a bendable form of concrete that is "500 times more resistant to cracking and 40 percent lighter in weight." This new type of concrete has substituted the gross aggregate normally used in the making of concrete, for thin fibers. Projects in Japan, Korea, Switzerland, and Australia have already used this new bendable concrete. Unfortunately, the country in which it was created has been slow to adopt its use.

BETÃO ORGÂNICO was created in 2005 by "Lisbon-based architects and designers e-studio." This organic concrete blends organic and inorganic material together to create a living surface. Concrete retains water, as such the concrete is used as a "battery" to provide water during dry spells for the plant life growing on it. Rather than having grass growing between concrete slabs, it is now possible to have the grass grow on the concrete slabs. These slabs could be added to outside walls to create living siding and provide plants to soak up CO2.

LiTraCon is a Hungarian concrete product developed seven years ago by architect Ron Losonczi. By impregnating the concrete with optical glass fibers, light can be transmitted from the outside in or inside out. This concrete has the same strength as regular concrete and will continue to transmit light through walls up to twenty meters (twenty-two feet) thick.

Finally, Tececo has developed an eco-cement that absorbs CO2 from the environment. By adding reactive magnesia to the cement, water and CO2 are absorbed and harden. Other waste products, such as "fly and bottom ash, slags, plastics, paper glass etc" can also be added to the cement without affecting the CO2 absorption.

These new types of cement and concrete give architects and designers more choices for creating truly different looks. Normally, you think of ugly concrete walls or slabs. Now concrete can not only be bent, but used as a basis for plants and light effects.

Development of new types of concrete with improved performance is a very important issue for the whole building industry. This development is based on the optimisation of the concrete mix design, with an emphasis not only to the workability and mechanical properties but also to the durability and the reliability of the concrete structures in general. Appearance of the new types of concrete requires a revision and improvement of existing structural systems and actual building technologies. The economical aspect are of importance as well.

TYPES OF CONCRETE

Ever since Thomas Edison patented Portland cement in 1907, it has been used for a variety of different uses. Sidewalks, buildings, sinks, and furniture are but a few of the products made from cement in the form of concrete. Cement is the dry powder that when mixed with other additives and water makes concrete. Over the past decade, new types of concrete and cement have been formulated that do everything from bend, to grow plants, and let light through.

BENDABLE CONCRETE :

The new concrete is 500 times more resistant to cracking and 40 percent lighter in weight. The materials in the concrete itself are designed for maximum flexibility. The Engineered Cement Composites technology has been used already on projects in Japan, Korea, Switzerland and Australia, but has had slow adoption in the US. Traditional concrete presents many problems: lack of durability and sustainability, failure under severe loading, and the resulting expenses of repair. ECC should address most of those problems. The ductile, or bendable, concrete is made mainly of the same ingredients in regular concrete minus the coarse aggregate. It looks exactly like regular concrete, but under excessive strain, the ECC concrete gives because the network of fibers veining the cement is allowed to slide within the cement, thus avoiding the inflexibility that causes brittleness and breakage.

The Michigan Department of Transportation (MDOT) used the ECC to replace part of a bridge that crosses Interstate 94. The slab eliminated the need for expansion joints, which are moveable steel teeth that separate sections of regular concrete. With the ECC, a longer continuous slab is possible.

The Mihara Bridge, a new structure in Hokkaido, Japan, has a deck of ECC that is a mere 2 inches (5 centimeters) thick.

Studies suggest ECC should last twice as long as regular concrete, but the researchers said more tests are needed to confirm that claim. Professor Victor Li estimates that over the course of 60 years, with servicing and replacement costs considered, a bridge made of ECC could be cost 37 percent less than a traditional span.

LITRACON :

LiTraCon ("light transmitting concrete") is a translucent concrete building material made of fine concrete embedded with 5% by weight of optical glass fibers. It was developed in 2001 by Hungarian architect Aron Losonczi working with scientists at the Technical University of Budapest.

The days of dull, grey concrete could be about to end. The Hungarian architect has combined the world's most popular building material with optical fibre from Schott to create a new type of concrete that transmits light.

A wall made of "LitraCon" allegedly has the strength of traditional concrete and an embedded array of glass fibers that can display a view of the outside world, such as the silhouette of a tree, for example. Thousands of optical glass fibres form a matrix and run parallel to each other between the two main surfaces of every block. Shadows on the lighter side will appear with sharp outlines on the darker one. Even the colours remain the same. This special effect creates the general impression that the thickness and weight of a concrete wall will disappear. The hope is that the new material will transform the interior appearance of concrete buildings by making them feel light and airy rather than dark and heavy.

In theory, a wall structure built out of the light-transmitting concrete can be a couple of meters thick as the fibers work without any loss in light up to 20 m. Load-bearing structures can also be built from the blocks as glass fibers do not have a negative effect on the well-known high compressive strength of concrete. The blocks can be produced in various sizes with embedded heat isolation too. Thousands of optical glass fibers form a matrix and run parallel to each other between the two main surfaces of each block. The proportion of the fibers is very small (4%) compared to the total volume of the blocks. Moreover, these fibres mingle in the concrete because of their insignificant size, and they become a structural component as a kind of modest aggregate. Therefore, the surface of blocks remains homogeneous concrete. It can be produced as prefabricated building blocks and panels. Due to the small size of the fibers, they blend into concrete becoming a component of the material like small pieces of aggregates. In this manner, the result is not only two materials- glass in concrete- mixed, but a third new material which is homogeneous in its inner structure and on its main surfaces as well.

The glass fibers lead light by points between the two sides of the blocks. Because of their parallel position, the light-information on the brighter side of such a wall appears unchanged on the darker side. The most interesting form of this phenomenon is probably the sharp display of shadows on the opposing side of the wall.

If more and more buildings begin using this technology, more natural light can be used to light offices and stores. This could lead to huge drops in the amount of electricity used to light buildings, since they'd be naturally lit during the day. Also, people who get exposure to the sun are generally happier and more productive, so that is another reason for businesses to use this light-transmitting concrete.

TECECO (porecocrete porous concrete) :

One particular eco-friendly product that is generating much attention is - Porecocrete Porous Concrete from Asset Rehabilitation / TecEco. By adding reactive magnesia to the cement, water and CO2 are absorbed and harden. Other waste products, such as "fly and bottom ash, slag, plastics, paper glass etc" can also be added to the cement without affecting the CO2 absorption. TecEco porecocretes represent a large-scale market for eco-cement. Porecocrete porous pavements mimic nature. Eco-cement sets by absorbing carbon dioxide, as by design it allows the entry of abundant quantities of the gas through what is an open pore structure. Using recycled aggregates, concrete cannot get much more sustainable. The main potential use for porecocretes is to make porous pavement in cities so that people are less affected by drought. These are pavements with lots of holes in them, and with subsurface drainage and usually a capacity to store water underneath or in a reservoir. Surface runoff water either soaks into an aquifer in suitable terrain or is captured above an impervious layer and drained preferably to underground storage for further use. Before infiltrating into the subsoil or sub-surface drainage the process improves water quality by providing surface area and aerobic conditions for cleansing. Some of the main advantages of Porecocrete Porous Concrete are that water penetrates through quickly leaving drier and safer surfaces with no standing water, and a reduction in noise pollution as porous pavements also absorb noise. Then it leads to less maintenance on nearby buildings and superstructure, as aquifers would be more regularly replenished resulting in less variable ground moisture content, reduced ground movement with wet dry cycles. Porous pavements made with TecEco Eco-Cements would not be attacked by salts and would last considerably longer than conventional binders such as bitumen (or asphalt) and Portland cement.

Heat is absorbed by pavements during hot, sunny days and due to the fact that we have paved all the ground, large cities just get hotter and hotter. The solution is to let the ground breathe and porous pavements do just that.

In Australia, some parts of the US and several other places in the world, it has been noted that subdivisions made with porous pavements that also have street trees can be several degrees cooler than surrounding suburbs.

How do Eco-Cements Work?

Eco-Cements are made by blending reactive magnesia with conventional hydraulic cements like Portland cement. It is not recommended that large amounts of pozzolan are added to an Eco-Cement as the pozzolan will compete with the carbonation reaction of lime and tend to block the carbonation affect slowing it down. Eco-Cements are environmentally friendly because in permeable substrates the magnesium oxide will first hydrate using mix water and then carbonate forming significant amounts of strength giving minerals in a low alkali matrix. Many different wastes can be used as aggregates and fillers without reaction problems. The reactive magnesium oxide used in Eco-Cements is currently made from magnesite (a carbonate compound of magnesium) found in abundance. In future TecEco hope to make it from abundant magnesium in sea water using the Greensols process.

When added to concrete magnesia hydrates to magnesium hydroxide, but only in permeable materials like bricks, blocks, pavers and pervious pavements will it absorb CO2 and carbonate. The greater proportion of the elongated minerals that form is water and carbon dioxide. These minerals bond aggregates such as sand and gravel and wastes such as saw dust, slag, bottom ash, plastics, paper etc. Eco-Cement can include more waste than other hydraulic cements like Portland cement because it is much less alkaline, reducing the incidence of delayed reactions that would reduce the strength of the concrete. Portland cement concretes on the other hand can't include large amounts of waste because the alkaline lime that forms causes delayed and disruptive reactions

Eco-Cement Carbonation

The more magnesia added to Eco-Cement and the more permeable it is, the more CO2 that is absorbed. The rate of absorption of CO2 varies with the degree of permeability. Carbonation occurs quickly at first and more slowly towards completion. A typical Eco-Cement concrete block would be expected to fully carbonate within a year. Eco-Cement also has the ability to be almost fully recycled back into cement, should the concrete structure become obsolete. .

Steps involved in making Eco-Cement

1. Magnesite (a compound of magnesium) is heated in a kiln to around 600 to 750 degrees C.

The lower firing temperature of the Tec-Kiln makes it easier to use free energy such as wind or solar or even waste energy and TecEco plan to make a kiln that does not use fossil fuels and in which the CO2 gases produced from the magnesium carbonate as it decomposes is captured and contained for further use or safe disposal.

2. Grinding in the hot area of the Tec-Kiln will result in increased efficiency.

3. The heating process produces reactive magnesium oxide (magnesia).

4. The reactive magnesia powder is added to a pre-determined, but variable amount of hydraulic cement such as Portland cement, and if desired, supplementary cementitious materials like fly ash.

5. The resulting blended powder is Eco-Cement.

6. When mixed with water and aggregates such as sand, gravel and wastes, Eco-Cement concretes are ready for pouring into concrete, pressing into blocks or other uses.

BETAO ORGANICO :

This type of concrete was created in 2005 by "Lisbon-based architects and designers e-studio." This organic concrete blends organic and inorganic material together to create a living surface. Concrete retains water, as such the concrete is used as a "battery" to provide water during dry spells for the plant life growing on it. Rather than having grass growing between concrete slabs, it is now possible to have the grass grow on the concrete slabs. These slabs could be added to outside walls to create living siding and provide plants to soak up CO2.

SPRAYED CONCRETE :

The technique of sprayed concrete has been in use for over 50 years in construction, structural repairs and a variety of other applications. The use of properly applied sprayed concrete is now recognised as being a technically sound and economic method of applying concrete both for effective repairs and for new constructions. The sprayed concrete forms and excellent bond with itself, concrete and masonry. The material is compacted onto the substrate under its own momentum, resulting in a strong, dense product with good resistance to abrasion and weathering. Sprayed concrete is extremely versatile and as a free forming material lends itself to use in the construction industry. This imperviousness and low water cement ratio gives a durable concrete with a host of proven applications. In many cases sprayed concrete will out-perform traditional concrete both in strength and permeability. The elimination of form work, the speed of application, the small access required and the ability to have the spraying machine and materials over 200 metres from the point of application, result in a large cost saving over other techniques. With the ever-increasing structural loadings, the technique has proven particularly suitable for the strengthening of bridges, tunnels and culverts.

The Phaeno Science Center, designed by Zaha Hadid, is the largest building in Europe constructed from self-consolidating concrete, which requires no vibration to eliminate air pockets and even out distribution of aggregates. SCC can be placed at a faster rate with no mechanical vibration and less screeding, allows shorter construction periods, permits structural and architectural shapes and surface, not achievable with conventional concrete.

Emmanuel Combarel and Dominique Marrec, two French architects, used Ductal, a high-performance concrete created by Lafarge in 2001, to build the RATP Bus Center in Thiais,

HIGH PERFORMANCE CONCRETE:

It is a relatively new term used to describe concrete that conforms to a set of standards above those of the most common applications, but not limited to strength. While all high-strength concrete is also high-performance, not all high-performance concrete is high-strength. Some examples of such standards currently used in relation to HPC are:

Ease of placement

Compaction without segregation

Early age strength

Long-term mechanical properties

Permeability

Density

Heat of hydration

Toughness

Volume stability

Long life in severe environments

SHOTCRETE :

Shotcrete uses compressed air to shoot (cast) concrete onto (or into) a frame or structure. Shotcrete is frequently used against vertical soil or rock surfaces, as it eliminates the need for formwork. It is sometimes used for rock support, especially in tunnelling. Today there are two application methods for shotcrete: the dry-mix and the wet-mix procedure. In dry-mix the dry mixture of cement and aggregates is filled into the machine and conveyed with compressed air through the hoses. The water needed for the hydration is added at the nozzle. In wet-mix, the mixes are prepared with all necessary water for hydration. The mixes are pumped through the hoses. At the nozzle compressed air is added for spraying. For both methods additives such as accelerators and fiber reinforcement may be used.

The term Gunite is occasionally used for shotcrete, but properly refers only to dry-mix shotcrete, and once was a proprietary name.

PERVIOUS CONCRETE:

Pervious concrete is sometimes specified by engineers and architects when porosity is required to allow some air movement or to facillitate the drainage and flow of water through structures. Pervious concrete is referred to as "no fines" concrete because it is manufactured by leaving out the sand or "fine aggregate". A pervious concrete mixture contains little or no sand (fines), creating a substantial void content. Using sufficient paste to coat and bind the aggregate particles together creates a system of highly permeable, interconnected voids that drains quickly. Typically, between 15% and 25% voids are achieved in the hardened concrete, and flow rates for water through pervious concrete are typically around 480 in./hr (0.34 cm/s, which is 5 gal/ft²/ min or 200 L/m²/min), although they can be much higher.

Both the low mortar content and high porosity also reduce strength compared to conventional concrete mixtures, but sufficient strength for many applications is readily achieved. Pervious concrete pavement is a unique and effective means to address important environmental issues and support sustainable growth. By capturing rainwater and allowing it to seep into the ground, porous concrete is instrumental in recharging groundwater, reducing stormwater runoff, and meeting US Environmental Protection Agency (EPA) stormwater regulations. The use of pervious concrete is among the Best Management Practices (BMPs) recommended by the EPA, and by other agencies and geotechnical engineers across the country, for the management of stormwater runoff on a regional and local basis. This pavement technology creates more efficient land use by eliminating the need for retention ponds, swales, and other stormwater management devices. In doing so, pervious concrete has the ability to lower overall project costs on a first-cost basis.

ROLLER-COMPACTED CONCRETE :

It is sometimes called rollcrete, is a low-cement-content stiff concrete placed using techniques borrowed from earthmoving and paving work. The concrete is placed on the surface to be covered, and is compacted in place using large heavy rollers typically used in earthwork. The concrete mix achieves a high density and cures over time into a strong monolithic block. Roller-compacted concrete is typically used for concrete pavement, but has also been used to build concrete dams, as the low cement content causes less heat to be generated while curing than typical for conventionally placed massive concrete pours.

GLASS CONCRETE:

The use of recycled glass as aggregate in concrete has become popular in modern times, with large scale research being carried out at Columbia University in New York. This greatly enhances the aesthetic appeal of the concrete.

ASPHALT CONCRETE

Strictly speaking, asphalt is a form of concrete as well, with bituminous materials replacing cement as the binder.

RAPID STRENGTH CONCRETE

This type of concrete is able to develop high resistance within few hours after been manufactured. This feature has advantages such as removing the formwork early and to move forward in the building process at record time, repair road surfaces that become fully operational in just few hours.

RUBBERIZED CONCRETE

While " rubberised concrete" is common, rubberized Portland cement concrete ("rubberized PCC") is still undergoing experimental tests, as of 2007 .

POLYMER CONCRETE

Polymer concrete is concrete which uses polymers to bind the aggregate. Polymer concrete can gain a lot of strength in a short amount of time. For example, a polymer mix may reach 5000 psi in only four hours. Polymer concrete is generally more expensive than conventional concretes.

High-Strength Concrete

A concrete of high strength can be made without admixtures provided it is mixed with low amounts of water and has desirable workability characteristics. At low water. cement ratios however, it is not easy to achieve good workability. As water reductions of about 25 to 30 per cent can be achieved by using superplasticizers without loss in workability characteristics, significantly higher initial and ultimate strengths are realized. Although high cement content may also be used to obtain high initial strengths in concrete, the higher heat developed by the chemical reactions produces undesirable cracks and shrinkage.

High early strength development, a characteristic of concrete made using superplasticizers at low water:cement ratios, is particularly advantageous in the production of precast units. For prestressed beams and units, which need overnight heat-curing, use of superplasticizers allows reduction in curing time and curing temperatures. High early strengths are particularly useful for placing concrete in traffic areas such as city roads and airport runways. Pumping at reduced water content is also facilitated by the use of superplasticizers.

In the early 1970s, experts predicted that the practical limit of ready-mixed concrete would be unlikely to exceed a compressive strength greater than 11,000 psi (76 MPa). Over the past two decades, the development of high-strength concrete has enabled builders to easily meet and surpass this estimate. Two buildings in Seattle, Washington, contain concrete with a compressive strength of 19,000 psi (131 MPa).

The primary difference between high-strength concrete and normal-strength concrete relates to the compressive strength that refers to the maximum resistance of a concrete sample to applied pressure. Although there is no precise point of separation between high-strength concrete and normal-strength concrete, the American Concrete Institute defines high-strength concrete as concrete with a compressive strength greater than 6000 psi (41 MPa).

Manufacture of high-strength concrete involves making optimal use of the basic ingredients that constitute normal-strength concrete. Producers of high-strength concrete know what factors affect compressive strength and know how to manipulate those factors to achieve the required strength. In addition to selecting a high-quality portland cement, producers optimize aggregates, then optimize the combination of materials by varying the proportions of cement, water, aggregates, and admixtures.

When selecting aggregates for high-strength concrete, producers consider the strength of the aggregate, the optimum size of the aggregate, the bond between the cement paste and the aggregate, and the surface characteristics of the aggregate. Any of these properties could limit the ultimate strength of high-strength concrete.

Admixtures

Pozzolans, such as fly ash and silica fume, are the most commonly used mineral admixtures in high-strength concrete. These materials impart additional strength to the concrete by reacting with portland cement hydration products to create additional C-S-H gel, the part of the paste responsible for concrete strength.

It would be difficult to produce high-strength concrete mixtures without using chemical admixtures. A common practice is to use a superplasticizer in combination with a water-reducing retarder. The superplasticizer gives the concrete adequate workability at low water-cement ratios, leading to concrete with greater strength. The water-reducing retarder slows the hydration of the cement and allows workers more time to place the concrete.

High-strength concrete is specified where reduced weight is important or where architectural considerations call for small support elements. By carrying loads more efficiently than normal-strength concrete, high-strength concrete also reduces the total amount of material placed and lowers the overall cost of the structure.

The most common use of high-strength concrete is for construction of high-rise buildings. At 969 ft (295 m), Chicago's 311 South Wacker Drive uses concrete with compressive strengths up to 12,000 psi (83 MPa) and is the tallest concrete building in the United States.

HIGH SRENGTH LIGHT WEIGHT CONCRETE

Lightweight concrete has been used successfully for many years for structural members in high-rise buildings. In addition to its lighter weight, which permits saving in dead load and this concrete provides better heat insulation than normal weight concrete. In recent years, the applications of high-strength concrete have increased, and high-strength concrete has now been used in many part of the world. However, not enough significant data of high-strength lightweight concrete with compressive strength in excess of 60 N/mm2 have been obtained. This report summarizes results of an experimental study of the properties of hardened high-strength lightweight concrete such as strength, drying shrinkage, durability and porosity, and provides important new information on the mix proportion and curing method of this concrete. These results are as follows; (a) In regard to porosity of lightweight aggregate, it was observed the tendency that expanded shale type has a lager radius than that of sintered fly ash type, it depends on aggregate characteristics, surface texture and void connection. (b) Different water content of lightweight aggregate gives influence to porosity of mortar matrix under drying condition. (c) Resistance of freezing and thawing or fire of light weight aggregate concrete is not necessary to advance under moisture condition, because of light weight aggregates, due to their cellular structure, capable of containing more water than normal weight aggregate. (d) As the consideration of the porosities and water content of hardened concrete, it was evaluated the properties of high-strength lightweight concrete. (author abst.)

Part of the results of an ongoing laboratory work carried out to design a structural lightweight high strength concrete ( SLWHSC ) made with and without mineral admixtures is presented. Basaltic-pumice ( scoria ) was used as lightweight aggregate.

A control lightweight concrete mixture made with lightweight basaltic-pumice (scoria) containing normal Portland cement as the binder was prepared. The control lightweight concrete mixture was modified by replacing 20% of the cement with fly ash and by replacing 10% of the cement with silica fume. A ternary lightweight concrete mixture was also prepared modifying the control lightweight concrete by replacing 20% of cement with fly ash and 10% of cement with silica fume. Two normal weight concretes (NWC) were also prepared for comparison purpose.

Fly ash and silica fume are used for economical and environmental concerns. Cylinder specimens were cast from the fresh mixtures to measure compressive and flexural tensile strength. The concrete samples were cured at 65% relative humidity with 20 °C temperature. The density and slump workability of fresh concrete mixtures were also measured.

Laboratory test results showed that structural lightweight concrete (SLWC) can be produced by the use of scoria. However, the use of mineral additives seems to be mandatory for production of SLWHSC. The use of ternary mixture was recommended due to its satisfactory strength development and environmental friendliness.

Future construction of concrete floating platforms for offshore oil exploration off the east coast of Canada will lead to a substantial increase in the use of high-strength lightweight (HSLW) concrete. HSLW concrete has been extensively used in Norway and other parts of Europe. HSLW concrete with its high durability and lightweight characteristics is a very much sought after material in the construction of concrete floating platforms.

SELF CONSOLIDATING CONCRETE

Self-consolidating concrete, also known as self-compacting concrete and SCC, is a highly flowable, non-segregating concrete that can spread into place, fill formwork and encapsulate even the most congested reinforcement, all without any mechanical vibration. As a high-performance concrete, SCC delivers these attractive benefits while maintaining all of concrete's customary mechanical properties and durability characteristics.

SCC is defined as a concrete mixture that can be placed purely by means of its own weight, with little or no vibration. Adjustments to traditional mix designs and the use of superplasticizers creates flowing concrete that meets tough performance requirements. If needed, low dosages of viscosity modifier can be used to eliminate unwanted bleeding and segregation.

Since its inception in the 1980s, the use of SCC has grown tremendously. The

development of high performance polycarboxylate polymers and viscosity modifiers have made it possible to create "flowing" concrete without compromising durability, cohesiveness, or compressive strength. The flowability of SCC is measured in terms of spread when using a modified version of the slump test (ASTM C 143). The spread (slump flow) of SCC typically ranges from 18 to 32 inches (455 to 810 mm) depending on the requirements for the project. The viscosity, as visually observed by the rate at which concrete spreads, is an important characteristic of plastic SCC and can be controlled when designing the mix to suit the type of application being constructed.

SCC's unique properties give it significant economic, constructability, aesthetic and engineering advantages. SCC is an increasingly attractive choice for optimizing site manpower (through reduction of labor and possibly skill level), lowering noise levels, and allowing for a safer working environment. SCC allows easier pumping (even from bottom up), flows into complex shapes, transitions through inaccessible spots, and minimizes voids around embedded items to produce a high degree of homogeneity and uniformity. That's why SCC allows for denser reinforcement, optimized concrete sections and shapes, and greater freedom of design while producing superior surface finishes and textures.

HIGH PERFORMANCE CONCRETE

In recent years, the terminology "High-Performance Concrete" has been introduced into the construction industry. This edition of Technical Talk explains high-performance concrete and how it differs from conventional concrete.

The American Concrete Institute (ACI) defines high-performance concrete as concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely when using conventional constituents and normal mixing, placing and curing practices. A commentary to the definition states that a high-performance concrete is one in which certain characteristics are developed for a particular application and environment. Examples of characteristics that may be considered critical for an application are:

* Ease of placement

* Compaction without segregation

* Early age strength

* Long-term mechanical properties

* Permeability

* Density

* Heat of hydration

* Toughness

* Volume stability

* Long life in severe environments

Because many characteristics of high-performance concrete are interrelated, a change in one usually results in changes in one or more of the other characteristics. Consequently, if several characteristics have to be taken into account in producing a concrete for the intended application, each must be clearly specified in the contract documents.

A high-performance concrete is something more than is achieved on a routine basis and involves a specification that often requires the concrete to meet several criteria. For example, on the Lacey V. Murrow floating bridge in Washington State, the concrete was specified to meet compressive strength, shrinkage and permeability requirements. The latter two requirements controlled the mix proportions so that the actual strength was well in excess of the specified strength. This occurred because of the interrelation between the three characteristics. Other recent commercial examples where more than one characteristic was required are given in Table 1.

High-strength concrete A high-strength concrete is always a high-performance concrete, but a high-performance concrete is not always a high-strength concrete. ACI defines a high-strength concrete as concrete that has a specified compressive strength for design of 6,000 psi (41 MPa) or greater. According to a paper(1) by Paul Zia of North Carolina State University, other countries use a higher compressive strength in their definitions of high-strength concrete with 7,000 psi (48 MPa) minimum. Other countries also specify a maximum compressive strength, whereas the ACI definition is open-ended.

The specification of high-strength concrete generally results in a true performance specification in which the performance is specified for the intended application, and the performance can be measured using a well-accepted standard test procedure. The same is not always true for a concrete whose primary requirement is durability.

Durable concrete Specifying a high-strength concrete does not ensure that a durable concrete will be achieved. In addition to requiring a minimum strength, concrete that needs to be durable must have other characteristics specified to ensure durability. In the past, durable concrete was obtained by specifying air content, minimum cement content and maximum water-cement ratio. Today, performance characteristics may include permeability, deicer scaling resistance, freeze-thaw resistance, abrasion resistance or any combination of these characteristics. Given that the required durability characteristics are more difficult to define than strength characteristics, specifications often use a combination of performance and prescriptive requirements, such as permeability and a maximum water-cementitious material ratio to achieve a durable concrete. The end result may be a high-strength concrete, but this only comes as a by-product of requiring a durable concrete.

Concrete materials Most high-performance concretes produced today contain materials in addition to portland cement to help achieve the compressive strength or durability performance. These materials include fly ash, silica fume and ground-granulated blast furnace slag used separately or in combination. At the same time, chemical admixtures such as high-range water-reducers are needed to ensure that the concrete is easy to transport, place and finish. For high-strength concretes, a combination of mineral and chemical admixtures is nearly always essential to ensure achievement of the required strength. Examples of concrete mixes for durable and high-strength concrete are shown in Table 2.

Most high-performance concretes have a high cementitious content and a water-cementitious material ratio of 0.40 or less. However, the proportions of the individual constituents vary depending on local preferences and local materials. Mix proportions developed in one part of the country do not necessarily work in a different location. Many trial batches are usually necessary before a successful mix is developed.

High-performance concretes are also more sensitive to changes in constituent material properties than conventional concretes. Variations in the chemical and physical properties of the cementitious materials and chemical admixtures need to be carefully monitored. Substitutions of alternate materials can result in changes in the performance characteristics that may not be acceptable for high-performance concrete. This means that a greater degree of quality control is required for the successful production of high-performance concrete.

HIGH VOLUME FLY ASH CONCRETE

What is fly ash?

Fly ash is a by-product from coal-fired electricity generating power plants. The coal used in these power plants is mainly composed of combustible elements such as carbon, hydrogen and oxygen (nitrogen and sulfur being minor elements), and non-combustible impurities (10 to 40%) usually present in the form of clay, shale, quartz, feldspar and limestone. As the coal travels through the high-temperature zone in the furnace, the combustible elements of the coal are burnt off, whereas the mineral impurities of the coal fuse and chemically recombine to produce various crystalline phases of the molten ash. The molten ash is entrained in the flue gas and cools rapidly, when leaving the combustion zone (e.g. from 1500°C to 200°C in few seconds), into spherical, glassy particles. Most of these particles fly out with the flue gas stream and are therefore called fly ash. The fly ash is then collected in electrostatic precipitators or bag houses and the fineness of the fly ash can be controlled by how and where the particles are collected.

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The use of fly ash in concrete

Fly ash can be used in concrete as a partial replacement for ordinary portland cement (opc). Fly ash can be introduced in concrete directly, as a separate ingredient at the concrete batch plant or, can be blended with the opc to produce blended cement, usually called portland-pozzolana cement (ppc) in India. Fly ash blended cements are produced by several cement companies in India.

Generally speaking, currently in the concrete industry, the percentage of fly ash as part of the total cementing materials in concrete normally ranges from 15 to 25%, although it can go up to 30-35% in some applications. The use of fly ash in concrete will improve some aspects of the performance of the concrete provided the concrete is properly designed. The main aspects of the concrete performance that will be improved by the use of fly ash are increased long-term strength and reduced permeability of the concrete resulting in potentially better durability. The use of fly ash in concrete can also address some specific durability issues such as sulphate attack and alkali silica reaction. However, a few additional precautions have to be taken to insure that the fly ash concrete will meet all the performance criteria.

The table given below is a paper presented by Dr Wilbert Langley and Dr Gordon Leaman at the sixth CANMET/ ACI / JCI International Conference, held May 31 - June 5, 1998. These are the actual mixes used in demonstration projects throughout Canada to prove the practicality of using high-volume fly ash concrete for a variety of projects. The Parklane Development in Halifax, Nova Scotia, Canada is a seven story structure and was built with 55% high-volume fly ash concrete (high strength mix given in the table below) . Cast-in-place columns and beams were poured with concrete specified to meet design strengths of between 4,350 psi at 28 days and 7,250 psi at 120 days. Actual strengths developed exceeded required strengths by 30%-40% on an average

HIGH VOLUME FLY ASH CONCRETE

All mixes contained air entraining admixtures and superplasticizers

	Conventional Mix	Low Strength 55% Replacement	Medium Strength 55% Replacement	High Strength 55% Replacement
Total Cementitious Content (c+fa) (lb/cu.yd)	483	374	566	660
Cement (lb)	483	166	250	300
Class F Fly Ash (lb)	0	208	316	360
Sand (lb)	1334	1467	1250	1266
Stone (lb)	1700	1834	1834	1850
Water (lb)	220	185	198	185
Water to Cement Ratio	0.46	0.49	0.35	0.28

Compressive Strength (psi)
3 day	4,600	1,250	2,320	3,190
7 day	5,000	1,750	3,040	4,900
28 day	6,500	3,350	5,500	8,300
91 day	7,100	4,050	7,700	10,900
365 day	7,550	7,400	10,000	-

Set Time (hours:minutes)
Initial	6:25	8:25	5:35	-
Final	7:50	11:15	7:40	-

In the US, the State of Wisconsin has been using a 60% Class F fly ash in concrete mix since 1989. HVFA concrete has now found a commercial niche in the Sydney construction market and is being trialed for the Sydney Olympic facilities. For the Crown Casino project, Connell Wagner required highly durable and low drying shrinkage concrete for the construction of the 55,000 square meter basement that was located below the water table

Another benefit of using fly ash in concrete is that fly ash makes beautiful, "architectural" concrete. Fly ash of today is light in color and its extreme workability ensures smoother finishes. That most famous of architecturally exposed concrete buildings, the Jonas Salk Institute, was built with fly ash concrete. I have seen the NCCBM building located at Ballabhgarh & it still looks beautiful even after having weathered so many years.

Addition of fly ash in plaster virtually eliminates defects like crazing, map cracking, drying shrinkage cracks, debonding, grinning, expansion & popping.

SHRINKAGE COMPENSATION CONCRETE

Use of Shrinkage Compensating Concrete (SCC) In Pre-Stressed Concrete

PRE-STRESSED CONCRETE:

There are characteristics of shrinkage compensating concrete (SCC) that are similar to the objectives and methodology behind pre-stressed concrete. Pre-stressed concrete is defined as a concrete member with a pre-determined compressive force, or moment, built into the member so that the internal stresses, designed as a result of the members intended use, will be equal to or less then the pre-stressing stresses built into the member. Post-tensioning and pre-tensioning are methods of achieving pre-stressed concrete.

The objectives and methodology of using SCC to enhance the properties of concrete is very similar to the objectives and methodology of using pre-stressed to accommodate structural loadings. Shrinkage cracking control, combined with the other inherent advantages of SCC, make SCC a better material for pre-stressed concrete members.

SHRINKAGE COMPENSATING COMPONENT

ACI recognizes two methods of achieving SCC, ettringite crystal development or calcium hydroxide platelet crystal development. The inherent characteristics of the calcium hydroxide platelet system, developed by the use of CONEX, is the better system of the two due to its inherent likeness of chemical action during hydration of the cement in use. The advantages of the platelet SCC method makes it well suited for use in pre-stressed concrete in general and in post-tensioned concrete in particular.

DESIGN CRITERIA:

The primary design objective of pre-stressed concrete is to place a compressive force in the concrete member that would prevent the concrete from going into tension and failing under design load conditions. Failure usually being defined as tension or stress cracking occurring in the concrete member. The primary objective for using pre-stressed concrete is economic. This is due to the fact that a pre-stressed member, of the same physical dimensions as a conventional reinforced concrete member, will have a greater load carrying capability. Conversely, for a given design loading, a pre-stressed member will be smaller in dimension and weight then a conventional concrete reinforced member.

SCC - HOW IT WORKS:

Shrinkage compensating concrete (SCC) has a case history of placements free of shrinkage cracks due to the "pre-stressing" action (restrained expansion or RE) created within the concrete during hydration and curing. During this period several phenomena are taking place simultaneously within the concrete. The most important being expansion of the concrete matrix due to the chemical reaction of CONEX creating development of calcium hydroxide crystals, and bonding of the concrete to the reinforcing. While this is occurring, the RE created causes the concrete to go into compression. The calcium hydroxide system of expansion, that is the formation of the platelets that create the expansion, is approximately at the same rate as the curing of the concrete. As long as compressive stresses within the concrete are greater then the tensile stresses the concrete will remain in compression, and tension cracks will not appear. This characteristic is taken advantage of by using SCC in the construction of cast in place slabs on grade (warehouse floors, pavements, secondary containment structures for hazardous materials) and structural members (bridge decks, primary containment structures, buildings, etc.). The benefit of SCC in slabs on grade is the ability to place larger sections (i.e. 20,000 ft2 / 2,000 m2) without contraction joints and with a reduction, and often elimination, of edge curling. The advantage of using SCC in bridge deck and containment structures is the increase in imperviousness of the concrete as well as the lack of shrinkage cracking.

SCC AS APPLIED TO PRE-STRESSED CONCRETE:

Currently the use of SCC is expanding into the pre-cast industry and also into pre-stressed concrete applications. While there are examples of cast in place pre-stressed applications of SCC, it is still a long way off from being in general use. This is perhaps due to the lack of published data detailing the use of SCC in post-tensioned applications. Tests should be done to establish the required expansion for desired results. These tests would establish the amount of compressive stress in the member resulting from different dosages of CONEX and related degrees of post-tensioning. This would allow other member characteristics to be adjusted accordingly. An obvious goal of using CONEX is to increase the quality of an existing concrete product and/or reduce the production cost of that concrete product. The addition of CONEX will increase the internal compressive stresses in the post-tensioned concrete member(s) if the proper restraint is provided. How this will impact the member design and/or production methods will need to be developed, but it presents a different look at the potential of shrinkage compensation in pre-stressed concrete.

In general, CONEX SCC is similar to and compatible with pre-stressed concrete, and acts interdependently with the cement in use, developing the following advantages:

1. A pre-stressed member with a higher degree of internal compression to assure greater crack control.
2. More impermeable concrete.
3. Better edge finishing.
4. Possibly a way to reduce production costs through less breakage and discard.

FIBER REINFORCEMENTS

NON-STEEL REINFORCEMENT :

Some construction cannot tolerate the use of steel. For example, MRI machines have huge magnets, and require nonmagnetic buildings. Another example are toll-booths that read radio tags, and need reinforced concrete that is transparent to radio.

In some instances, the lifetime of the concrete structure is more important than its strength. Since corrosion is the main cause of failure of reinforced concrete, a corrosion-proof reinforcement can extend a structure's life substantially.

For these purposes some structures have been constructed using fiber-reinforced plastic rebar, grids or fibers. The "plastic" reinforcement can be as strong as steel. Because it resists corrosion, it does not need a protective concrete cover of 30 to 50 mm or more as steel reinforcement does. This means that FRP-reinforced structures can be lighter, have longer lifetime and for some applications be price-competitive to steel-reinforced concrete.

The main barrier to use of FRP reinforcement is the fact that it is neither ductile nor fire resistant. Structures employing FRP rebars may therefore exhibit a less ductile structural response, and decreased fire resistance.

However, the addition of short monofilament polypropylene fibers to the concrete during mixing may have the beneficial effect of reducing spalling during a fire. In a severe fire, such as the Channel Tunnel fire, conventionally reinforced concrete can suffer severe spalling leading to failure. This is in part due to the pore water remaining within the concrete boiling explosively; the steam pressure then causes the spalling

HISTORICAL PERSPECTIVE:

The concept of using fibers as reinforcement is not new. Fibers have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mud bricks. In the early 1900s, asbestos fibers were used in concrete, and in the 1950s the concept of composite materials came into being and fiber reinforced concrete was one of the topics of interest. There was a need to find a replacement for the asbestos used in concrete and other building materials once the health risks associated with the substance were discovered. By the 1960s, steel, glass (GFRC), and synthetic fibers such as polypropylene fibers were used in concrete, and research into new fiber reinforced concretes continues today.

EFFECTS OF FIBER IN CONCRETE:

Fibers are usually used in concrete to control plastic shrinkage cracking and drying shrinkage cracking. They also lower the permeability of concrete and thus reduce bleeding of water. Some types of fibers produce greater impact, abrasion and shatter resistance in concrete. Generally fibers do not increase the flexural strength of concrete, so it can not replace moment resisting or structural steel reinforcement. Some fibers reduce the strength of concrete.

The amount of fibers added to a concrete mix is measured as a percentage of the total volume of the composite (concrete and fibers) termed volume fraction (V_f). V_f typically ranges from 0.1 to 3%. Aspect ratio (l/d) is calculated by dividing fiber length (l) by its diameter (d). Fibers with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the modulus of elasticity of the fiber is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increase in the aspect ratio of the fiber usually segments the flexural strength and toughness of the matrix. However, fibers which are too long tend to "ball" in the mix and create workability problems.

Some recent research indicated that using fibers in concrete has limited effect on the impact resistance of concrete materials. This finding is very important since traditionally people think the ductility increases when concrete is reinforced with fibers. The results also pointed out that the micro fibers is better in impact resistance compared with the longer fibers.

The High Speed tunnel linings incorporated concrete containing 1 kg/m³ of polypropylene fibers, of diameter 18 & 32 μm, giving the benefits noted below.

Polypropylene fibers can:

Improve mix cohesion, improving pumpability over long distances

Improve freeze-thaw resistance

Improve resistance to explosive spalling in case of a severe fire

Improve impact resistance

Increase resistance to plastic

DEVELOPMENTS IN FIBER REINFORCED CONCRETE:

A new kind of natural fiber reinforced concrete (NFRC) made of cellulose fibers processed from genetically modified slash pine trees is giving good results. The cellulose fibers are longer and greater in diameter than other timber sources. Some studies were performed using waste carpet fibers in concrete as an environmentally friendly use of recycled carpet waste. A carpet typically consists of two layers of backing (usually fabric from polypropylene tape yarns), joined by CaCO₃ filled styrene-butadiene latex rubber (SBR), and face fibers (majority being nylon 6 and nylon 66 textured yarns). Such nylon and polypropylene fibers can be used for concrete reinforcement

High performance fiber reinforced cementitious composites (HPFRCCs):

This particular class of concrete was developed with the goal of solving the structural problems inherent with today's typical concrete, such as its tendency to fail in a brittle manner under excessive loading and its lack of long term durability. The two important properties of HPFRCC's are

The remarkable ability to strain harden under excessive loading.

In layman's terms, this means they have the ability to flex or deform before fracturing, a behavior similar to that exhibited by most metals under tensile or bending stresses. Because of this capability, HPFRCCs are more resistant to cracking and last considerably longer than normal concrete.

Their low density.

A less dense, and hence lighter material means that HPFRCCs could eventually require much less energy to produce and handle, deeming them a more economic building material. Because of HPFRCCs' lightweight composition and ability to strain harden, it has been proposed that they could eventually become a more durable and efficient alternative to typical concrete.

HPFRCCs include the following ingredients: fine aggregates, a superplasticizer, polymeric or metallic fibers, cement, and water. Thus the principal difference between HPFRCC and typical concrete composition lies in HPFRCCs' lack of coarse aggregates. Typically, a fine aggregate such as silica sand is used in HPFRCCs.

One aspect of HPFRCC design involves preventing crack propagation, or the tendency of a crack to increase in length, ultimately leading to material fracture. This occurrence is hindered by the presence of fiber bridging, a property that most HPFRCCs are specifically designed to possess. Fiber bridging is the act of several fibers exerting a force across the width of a crack in an attempt to prevent the crack from developing further. This capability is what gives bendable concrete its ductile properties.

Proposed uses for HPFRCCs include bridge decks, concrete pipes, roads, structures subjected to seismic and non-seismic loads, and other applications where a lightweight, strong and durable building material is desired. Though HPFRCCs have been tested extensively in the lab and been employed in a few commercial building projects, further long term research and real world application is needed to prove the true benefits of this material.

The newly developed fiber reinforced concrete is named as Engineered Cementitious Composite (ECC).

It is 500 times more resistant to cracking

It is 40 percent lighter than traditional concrete

It can sustain strain-hardening up to several percent strain, resulting in a material ductility of at least two orders of magnitude higher when compared to normal concrete.

It has unique cracking behavior . When loaded to beyond the elastic range, ECC maintains crack width to below 100 µm, even when deformed to several percent tensile strains.

ECC's tensile strain hardening behavior has a capacity in the range of 3-7%,which means that unlike common concrete, which is brittle and breaks under that amount of strain, ECC will bend under the same stress, like a piece of sheet metal. The high ductility is achieved by optimizing the microstructure of the composite employing micromechanical models. ECC looks exactly like regular concrete, but under excessive strain, the ECC concrete bends because the distinctively coated matrix of fibers in the cement is allowed to slide within the cement. ECC is made using the same ingredients of regular concrete but without the use of coarse aggregate.

ECC has already been used by the Michigan Department of Transportation to patch a portion of the Grove Street Bridge deck over Interstate 94. The ECC patch was used as a replacement to the previously existent expansion joint that linked two deck slabs. Expansion joints, commonly used in bridges to allow for the seasonal expansion and contraction of the concrete decks, are an example of a ubiquitous construction practice that could eventually be eliminated through the use of bendable concrete. Other existent structures composed of ECC, include the Curtis Road Bridge in Ann Arbor, MI and the Mihara Bridge in Hokkaido, Japan. The deck of the Mihara Bridge, composed of bendable concrete, is only five centimeters thick and has an expected lifetime of one-hundred years.

NANOMATERIALS

NANOTUBES AND NANOWIRES AS REINFORCEMENT:

In developing nano-composite materials, nanotubes and nanowires are expected to greatly improve the properties of the composites. Silicon carbide nanowires have been regarded as an excellent reinforcement for composites due to the high intrinsic strength of the materials. However, the silicon carbide nanowires have a smooth surface and are easily pulled out when the composites break because of the weak adhesion between the nanowires and the matrix. Therefore, we need to fabricate a contoured surface of the silicon carbide nanowires in order to improve the adhesion.

This led to the invention of a new type of silicon carbide nanowires – periodically twinned SiC nanowires, which have a contoured surface on the nanoscale. The nanowires – with a hexagonal cross section, a diameter of 50–300 nm and a length of tens to hundreds of micrometers – feature a zigzag arrangement of periodically twinned segments with a uniform thickness along the entire growth length. Computer simulation demonstrates that the zigzag columnar structure is formed by the stacking of hexagonal discs of {111} planes of SiC. A minimum surface energy and strain energy argument explain the formation of periodic twins in the SiC nanowires.

The twinning structure has made the nanowires exhibit different luminescence and chemical stability. A Chinese group showed that the silicon carbide nanowires with beaded morphology can greatly enhance the tensile strength of an epoxy composite. Therefore, the new type of twinned SiC nanowires is expected to find important applications in nano-composites.

MODIFICATION OF GLASSS FIBER USING PLAZMA POLYMERIZATION TECHNIQUE :

The plasma treated E-glass fiber improves the mechanical properties of acrylic resin denture base material, polymethylmethacrlyate (PMMA). Plasma surface treatment of fibers is used as reinforcement in composite materials to modify the chemical and physical properties of their surfaces with tailored fiber–matrix bonding strength.

Three different types of monomer 2-hydroxyethyl methacrylate (HEMA), triethyleneglycoldimethylether (TEGDME) and ethylenediamine (EDA) were used in the plasma polymerization modification of glass fibers. A radiofrequency generator was used to sustain plasma in a glass vacuum chamber. Glass fibers were modified at the same glow-discharge power of 25W and exposure time of 30min for each monomer. Fibers were incorporated into the acrylic with 1% (w/w) loading except control group. Specimens were prepared using a standard mould of 3cm×0.5cm×0.8cm in dimension with eight specimens in each group. Samples were subjected to a flexural strength test set up at a crosshead speed of 5mm/min. Scanning electron microscopy (SEM) was used to examine the microstructure and X-ray photoelectron

Concluding Remarks

It has long been a concrete technologist's dream to discover a method of making concrete at the lowest possible water: cement ratio while maintaining high workability. To a considerable extent this dream may be fulfilled with the advent of superplasticizers. They have added a new dimension to the application of admixtures, and have made it possible to produce concrete with compressive strength of the order of 90 MPa.

Superplasticizers have other possible applications. Energy conservation and diminishing supplies of high quality raw materials will increasingly necessitate the use of marginal quality cements and aggregates. In such instances the use of superplasticizers may permit production of concrete at low water:cement ratios that will be strong enough to meet normal performance requirements. There are literally countless possible applications of superplasticizers, for example, in the production of fly ash concrete, blast furnace slag cement concrete, composites with various types of fibres and lightweight concrete. In addition, the dispersing effect of superplasticizers is not limited to portland cement and may find application in other cementitious systems.

The fact that superplasticizers show remarkable advantages in producing concrete should not imply that there are no problems associated with their use. A satisfactory solution to the high rate of slump loss in superplasticized concrete is yet to be found and the relative effects of materials, production methods and external conditions that influence this phenomenon are not completely understood. Further study will be necessary of the compatibility of other admixtures such as retarders, accelerators and air-entraining agents in combination with superplasticizers. Though surface area, tricalcium aluminate, and sulphate contents seem to influence slump, no definite trend has been established.

Most available data on superplasticized concrete have been obtained using SMF- and SNF-based superplasticizers. Even within a single type, variations in behaviour have occurred, possibly because of the differences in molecular weight and in the type of cation associated with the superplasticizer. Consequently it is difficult to predict exactly the properties and behaviour of superplasticized concrete. As more data become available, especially on the long-term behaviour of these concretes, it will be possible to formulate standards and codes of practice. The future use of superplasticizers will, however, be dictated by cost factors (of admixture and operating costs) and by acceptance by industry

Insulated Concrete Forms

2012-02-19T20:17:00.000-08:00

Concrete forms have taken a new shape-and purpose. Insulating concrete forms (ICFs) are rigid plastic foam forms that hold concrete in place during curing and remain in place afterwards to serve as thermal insulation for concrete walls. The foam sections are lightweight and result in energy-efficient, durable construction.

ICFs consist of insulating foam, commonly expanded polystyrene (EPS) or extruded polystyrene (XPS). The three basic form types are hollow foam blocks, foam planks held together with plastic ties, and 4 x 8 panels with integral foam or plastic ties. ICFs can be used to form various structural configurations, such as a standard wall, post and beam, or grid. They provide backing for interior and exterior finishes.

Insulation values of ICF walls vary depending on the material and its thickness. Typical insulation values range from R-17 to R-26, compared to between R-13 and R-19 for most wood-framed walls. The strength of ICF structures relative to lumber depends on configuration, thickness, and reinforcement. However, ICF walls are designed as reinforced concrete, having high wind and seismic resistance.

There are many ICF wall types. Products are differentiated based on the type of form and the shape of the concrete sections. Products are further differentiated by how forms attach to each other, how finishes are attached to the wall, insulating values, foam types and other features.

Basic Material Used:

Insulated concrete forms (ICFs) are hollow, lightweight forms manufactured

using two 21/2 inch (63.5m), 1.5lbs/cu.ft density expanded polystyrene (EPS) panels

which are connected by uniquely designed, high impact polypropylene webs. During

construction, the forms are stacked then filled with concrete making stable, durable

and sustainable walls.

The following are basic components of ICF system,

Basic Components of ICF System

§ Formwork (Stay-In-Place)

¢ Plastic

¢ Expanded Polystyrene

¢ Extruded Polystyrene

§ Concrete (Cast-In-Place)

§ Steel reinforcement

Structural Design of ICFs Covered by Prescriptive Method

Where the IRC and Prescriptive Method are not yet accepted, when certain ICF types are not covered by the Prescriptive Method, or when buildings do not meet the applicability limits of the Prescriptive Method, engineered designs (usually with sealed sets of plans) may be necessary in order to obtain building permits. For systems and applications that are not covered by the requirements in the Prescriptive Method, the NAHB Research Centre, under sponsorship of the Portland Cement Association (PCA), completed the publication entitled Structural Design of Insulating Concrete Form Walls in Residential Construction. This publication, available from PCA, is a guideline for the design of single- and multi-unit residential structures using ICF wall systems. It includes step-by-step design procedures for ICF, a comprehensive design example, and many design aids, such as graphs, charts, and tables, to assist design professionals.

Most ICF manufacturers have taken steps of their own to have their proprietary systems approved by various model code organizations. Evaluation Reports produced by code bodies are available from those manufacturers. Most ICF manufacturers will also provide design services if necessary.

Types of ICF Systems

ICF are basically forms for poured concrete walls that stay in place as a permanent part of the wall assembly. The forms, made of foam insulation, are either pre-formed interlocking blocks or separate panels connected with plastic ties. The left-in-place forms not only provide a continuous insulation and sound barrier, but also a backing for drywall on the inside, and stucco, lap siding, or brick on the outside.

Although all ICFs are identical in principle, the various brands differ widely in the details of their shapes, cavities and component parts. Block systems have the smallest individual units, ranging from 8" x 1'4" (height X length) to 1'4" x 4'. A typical ICF block is 10" in overall width, with a 6" cavity for the concrete. The units are factory-moulded with special interlocking edges that allow them to fit together many like plastic children blocks.

Panel systems have the largest units, ranging from roughly 1' x 8' to 4' x 12'. Their foam edges are flat, and interconnection requires attachment of a separate connector or "tie." Panels are assembled into units before setting in place - either on-site or by the local distributor prior to delivery.

Plank systems are similar to panel systems, but generally use smaller faces of foam, ranging in height from 8" to 12"and in width from 4' to 8'. The major difference between planks and panels is assembly. The foam planks are outfitted with ties as part of the setting sequence, rather than being pre-assembled into units.

Within these broad categories of ICFs, individual brands vary in their cavity design. "Flat wall" systems yield a continuous thickness of concrete, like a conventional poured wall. "Waffle grid wall" systems have a waffle pattern where the concrete is thicker at some points than others. "Screen grid" systems have equally spaced horizontal and vertical columns of concrete which are completely encapsulated in foam. Whatever the differences among ICF brands, all major ICF systems are engineer-designed, code-accepted, and field-proven.

Three Major types of ICF Systems are,

Screen grid OR Post-and- Beam (1^st Generation)

Waffle grid (2^nd Generation)

Flat (3^rd Generation)

Key Features of each system,

1. Screen grid OR Post-and- Beam (1^st Generation)

Ø Post and Beam Arrangement

Ø Most Versatile Because of its Stability and Strength

Ø While structurally Stronger Actually Lighter in Overall weight than other ICFs, this Factor make Batter in Seismic Prone Zone.

2. Waffle grid (2nd Generation)

Ø Closely Spaced vertical and Horizontal members with a concrete web between Members.

Ø Structurally Strong

3. Flat ICF System (2nd Generation)

Ø Flat wall ICF are System In Which the concrete within the form is uniform thickness throughout.

Ø It Requires Substantial Amount of Bracing.

Ø Ease to Pour Concrete

Ø Ease for the Lintel design Also

Manufacturer of ICF Systems

AMVIC

REDDIFORM

ARXX

Tools for Block Installation

§ Hand saw, folding pruning saw or conventional rip saw

§ Portable power saw

§ Keyhole saw

§ Table saw (optional)

§ Tape measure

§ Cordless driver drill and appropriate bits

§ Hammer drill

§ Reinforcing steel tie tools

§ Hammer

§ Framing square

§ 2 ft Spirit Level

§ 6 ft Spirit Level

§ Laser level, water level, or transit

§ Plumb bob

§ Mason's line (Enough to circle entire structure)

§ Chalk line

§ Foam gun

§ Reinforcing steel bender and cutter

§ Scaffold planks

§ Wall alignment & bracing system

§ Steel Stakes to anchor alignment braces (n/a if bracing off a slab)

Tools for Concrete Pour

§ Concrete Vibrator, 1 inch to 11/4 inch (25 to 32mm) head

– 10 to14 ft (3 to 4.2m) flexible shaft

§ Rubber gloves

§ Hard hats

§ Concrete finishing tools

§ Flat shovels for spill cleanup

Tools for Utility Installation

§ Hot Knife (for electric box cutout)

§ Electric chain saw (for cutting Romex wiring and plumbing channels)

§ Foam gun & Foam

Materials list

§ Reinforcing steel as required and accessories, e.g. ties, stirrups.

§ Screws to attach alignment bracing to ICF blocks (15/8 inch, 21/2 inch, #10 coarse thread)

§ Concrete Screws 11/2 to 13/4 inch to attach foot of alignment braces to concrete slab (TAPCON brand or equivalent)

§ Material for rough openings (i.e. 2x10, 2x6, etc.) lumber or plywood for fabricating wood bucks or vinyl bucks

§ Tie wire in rolls and in pre-made reinforcing steel tie loops

§ Anchor bolts, nuts, and washers or Simpson Strong-tie® ICFLC ledger connectors

§ Sleeves for mechanical and/or electrical fixtures

§ OSB or plywood for bridging cut joints, or removed webs, block outs for anchor bolts, etc.

§ Foam 2 Foam® EPS controlled-expansion foam/adhesive

§ Waterproofing / Damp Proofing system

ICF Advantages ……

Concrete Homes save Energy

Building a concrete home with insulating concrete forms (ICFs) saves energy and money. The greater insulation, tighter construction, and temperature-smoothing mass of the walls conserve heating and cooling energy much better than conventional wood-frame walls. This reduces monthly fuel bills. It also allows use of smaller heating and cooling equipment, saving money in construction.

Houses built with ICF exterior walls require an estimated 44% less energy to heat and 32% less energy to cool than comparable frame houses. A typical 2000 square foot home in the center of the U.S. will save approximately $200 in heating costs each year and $65 in air conditioning each year.

The bigger the house the bigger the savings. In colder areas of the U.S. and Canada, heating savings will be more and cooling savings less. In hotter areas, heating savings will be less and cooling savings more

Comfort and Quiet with Concrete Homes

Concrete walls built with insulating concrete forms effectively buffer a home's interior from the outdoors. The thick ICF sandwich of a massive material (concrete) with a light one (foam) sharply cuts fluctuations in temperature, air infiltration, and noise. They keep the inside of a house more comfortable and quiet than ordinary wood frame walls.

Greater Strength

– Storm resistant - rated for a 250MPH wind load

– Blast Tested [Force Protection Equipment Demonstration (FPED V) April 26–28, 2005]

Better Fire Protection

– UL listed at 3 hours with ½" drywall; 4 hours with 5/8" type x gypsum

Quieter

– Sound Transmission Class rating of 50 or greater

Reduced Maintenance

– Conventional construction is prone to maintenance problems such as drywall pops and basement leaks

Resistant to pests

– ICFs provide no food source and contain nothing to attract termites and other pests

Resistant to mold

– the concrete, foam and steel in an ICF wall are not a food source for mold growth, unlike wood and other organic materials; the airtight nature of the ICF structure also provides for better moisture control, further reducing the chance for mold to occur

PROJECT SCHEDULE CONTROL

2012-02-19T20:12:00.001-08:00

The first step in establishing a project is to estimate how long each activity will take, from the time it is started until the time it is finished. This duration estimate for each activity is the time for the work to be done plus associated waiting time.

An activity duration estimate must be based on the quantity of resources expected to be used on the activity. Throughout the performance of the project some activities will take longer than their estimated duration, others will be done in less time than their estimated duration, and a few may conform to duration estimates exactly. Over the life of a project that involves many activities, such delays and accelerations will tend to cancel out one another.

PROJECT CONTROL:

The key to effective project control is to measure actual progress and compare it to planned progress on a timely and regular basis and to take necessary corrective action immediately. The project schedule control process involves regularly gathering data on project performance, comparing with the planned performance. This process must occur regularly throughout the project.

It starts with establishing a baseline plan that shows how the project scope will be accomplished on time and within the budget. Once this baseline plan is agreed with the customer the project starts. A regular reporting period should be established for comparing the actual progress with the planned progress. Reporting may be daily, weekly, or monthly depending on the complexity and the duration of the project. During each reporting period, two kinds of data or information need to be collected.

1. Data on actual performance.

2. Information on any changes to the project scope, schedule or budget.

Once the updated schedule and budget have been calculated, they need to be compared with the baseline schedule and budget and analyzed for variances to determine whether the project is ahead or behind the time schedule. The project control process continues throughout the project.

APPROACHES TO SCHEDULE CONTROL:

Schedule control includes four steps

1. Analyzing the schedule to determine which areas need corrective action.
2. Deciding what specific corrective actions should be taken.
3. Revising the plan to incorporate the chosen corrective actions.
4. Recalculating the schedule to evaluate the efforts of the planned corrective actions.

If the planned corrective actions do not result in an acceptable schedule these steps are repeated. It is necessary to analyze the newly calculated schedule to determine whether it needs further attention. The schedule analysis should include identifying critical path and any path of activities.

CONTROLLING THE PROJECT SCHEDULE:

The managing and maintaining the schedule proactively is your best way to assure the project comes in on time. In order to be proactive about this process there are some inputs that one needs to understand.

Ø The inputs are:

· The Schedule Baseline - The schedule baseline is the current approved version of the project schedule which provides a basis for comparing and reporting on the project performance. The project schedule details the planned start and end dates for the activities.

· Performance Reports – Performance reports are first and foremost a communication mechanism to list what work has been performed by whom. A good performance report should show the planned and actual dates and duration of work activities

· Schedule Management Plan – The Schedule Management Plan details how changes to the schedule can be made and under which conditions such changes are allowed. Project Manager, Project Sponsors, and Functional Managers should adhere to the scheduling guidelines explained within the schedule management plan.

· Approved Change Requests - Approved schedule change requests are an input because the schedule needs to be revised to reflect the approved changes to the project schedule.

Once all of the inputs have been obtained, there are tools and techniques that can be used to review the schedule. If a situation occurs where project performance differs from the schedule, these tools and techniques can be used to correct the situation. Project managers will evaluate how much work has been completed compared with actual performance versus planned performance. If they uncover a schedule variance, the project manager should analyze the variance’s severity.

Ø The tools and techniques commonly employed in controlling the schedule are:

· Progress reporting – Progress Reporting is when a report is created detailing the actual start and finish dates of activities and the remaining duration of unfinished activities. It is a good idea to include the percent complete of activities in the progress report.

· Variance Analysis – Variance analysis compares planning data with actual performance in order to discover delays or variations in the project schedule. For example the planned start, duration, and anticipated completion date would be compared with the actual start date, duration, and completion date for that activity.

· Performance Measurement - Performance measurement assesses the severity of delays and other deviations by measuring project performance compared against the project plan. This comparison helps the project manager determine if corrective or proactive actions are need for this project. Some common performance measurement tools are:

1. Schedule comparison bar charts – Schedule comparison bar charts are a way to visualize the differences between the planned and actual performance. This is a good tool to graphically communicate project status.

2. Project Management Software – PMIS is utilized to determine the affect of variance upon individual activities. The PMIS easily calculates the impact of any proposed change to the schedule.

3. Schedule change control systems – Schedule change control systems are described in the project management plan with the integrated change control process. The schedule change control system is the bought into, agreed with, and realistic process to change the schedule. When project managers discover that actual performance is not meeting the schedule, it is a good idea to use the schedule change management process to propose changes to the schedule.

4. Schedule variance and the Schedule Performance Index - Schedule variance and the Schedule Performance Index both measure the financial value of the work performed as of a given date.

SV = EV – PV

SPI = EV / PV

Schedule variance and the Schedule Performance Index yield information on the current conditions of the project and can be used to determine whether the project is on or off schedule.

Ø The process of controlling the schedule creates several different types of outputs as follows:

· Performance measurements - The process of controlling the schedule produces measurements of performance to date on a project. The Schedule Variance and Schedule Performance Index are objective measures of project performance that can be used to report the status of the project to stakeholders.

· Requested changes – Requested changes are the proposed changes to start dates, finish dates, activity durations, or project milestones.

· Recommended corrective actions – Recommended corrective actions are changes to resolve a situation with the project schedule.

· Schedule Baseline updates – Schedule Baseline updates are done when approved changes are applied to the existing baseline.

· Activity List updates – Activity List updates occur when an approved change causes the project manager to add or remove activities from the Activity List.

· Activity attribute updates – Activity attribute updates are updates or changes in the description or relationship of project activities. These changes may require additional actions by some stakeholders, so they have to be communicated.

· Project Management Plan - Finally, the process of controlling the schedule may generate changes to the overall Project Management Plan. Corrective actions and approved schedule changes may call for changes in the methods, policies, and activities the project manager uses to control the schedule for the remainder of the project. These changes should be documented in the Schedule Management Plan segment of the Project Management Plan.

VARIANCE ANALYSIS:

The difference between the costs detailed in the plans and the actual costs is called variance. In order to calculate variance, up to date and accurate information is essential - providing a clear picture of the extent to which tasks are complete and the expense incurred to date. Clearly variance can be calculated for those tasks that have been completed, but for tasks that are partially completed the calculations are more complicated. A positive variance indicates that a project is under-spending whereas a negative variance indicates that a project is suffering from over-spend.

· Applying Variance:

Variance can be used to quantify the difference between the planned costs and the current planned costs, at whatever level is required - for example, for the project as a whole, for a sub-project, a group of related tasks or for individual tasks. Variance is usually expressed as a percentage, enabling the divergence to be quantified in proportional terms.

· Limitations of Variance Analysis:

This variance analysis can lead to the identification of certain types of task that frequently overrun their budget whilst other tasks may be seen to regularly come in under their budget. Occurrences such as these require further investigation in order to identify potential efficiency gains. The major problem with a variance analysis approach to project monitoring is the amount of time it takes to establish actual costs. On the majority of large projects, supported by a typical accounts department, there will be a time lag of around 6 weeks before spend information can be accurately reported.

EARNED VALUE ANALYSIS (EVA)

· The Practical Benefits of EVA:

The major problem with a simple variance analysis approach to project monitoring is the amount of time it takes to establish actual costs. Earned value analysis(EVA), represents a practical approach to measuring the progress of a project against the plans and this approach is based on variance analysis. Since EVA relies on the measurement of the actual amount of work that has been done at a given date and the multiplication of this by the associated cost rates, many of the delays associated with variance analysis can be eliminated.

Tasks that have not been started or that have been completed are relatively easy to quantify in terms of earned value. However, for tasks which have started but are not yet complete the situation is less clear and the problem of quantifying the earned value is compounded if tasks of long duration are involved. Therefore EVA is made easier by having a larger number of shorter tasks in the plan.

· The Earned Value Analysis Variables:

The earned value approach to project control overcomes the problem of managers making decisions based on isolated information. The three basic variables relating to budgetary and actual costs are defined on this screen. These variables can be used to analyze the project, at any level, to establish a variety of useful parameters.

o Budgeted Cost for Work Scheduled (BCWS) is the value of work that should have been done at a given point in time. It indicates the budget and work targets at a given point.

o Budgeted Cost for Work Performed (BCWP) is the value of work actually done at a given point in time. It takes the work that has been done and the budget for each task and indicates what portion of the budget should have been spent to achieve it. This variable is sometimes referred to as Earned Value.

o Actual Cost for Work Performed (ACWP) is the actual cost of the work done and it may vary from that budgeted. ACWP is the amount reported as actually expended in completing the work accomplished within a given time period.

o Earned Value(EV) = percentage complete multiplied by the budget, as defined by the Budgeted Cost for Work Scheduled (in either cost or man-hour terms).

o Planned Value (PV) represents the amount of time which reaching the project’s current progress should have taken to achieve according to the project management’s schedule.

Example: If, at a specific point of time, a project has a BCWP of Rs.25,000 and a BCWS of Rs.30,000 then it has a schedule variance (cost) of minus Rs.5,000 and a percentage variance of -16.6%. In other words it is behind schedule by 16.6%. The conversion to a percentage is done to avoid confusion, that is, the use of cost units to represent schedule variances.

FORMULAE:

1) SCHEDULE VARIANCE (SV):

“Schedule variance is a measure of the deviation between the actual progress and the planned progress. This is usually measured in units of cost rather than time.” The schedule variance (cost) can be established at any point in time by referring to the difference between BCWS and BCWP.

Schedule Variance can be calculated as using the following formula:

· Schedule Variance (SV) = Earned Value (EV) - Planned Value (PV)

· Schedule Variance (SV) = BCWP - BCWS

The formula mentioned gives the variance in terms of cost which will indicate how much cost of the work is yet to be completed as per schedule or how much cost of work has been completed over and above the scheduled cost.

· Positive Schedule Variance Indicates we are ahead of schedule

· Negative Schedule Variance Indicates we are behind of schedule

It is unwise to accept any variance as the norm. To put this in perspective:

· A contractor is reporting a SV of .89 actually means that for every £1.00 you pay him, you are receiving £0.89p in return. This must be questioned until a satisfactory answer and recovery plan are put in place.

· The converse is also unacceptable. If a contractor continuously reports a SV of >1 then we could be looking at a relaxed schedule or a new way of working that will render the baseline plan irrelevant. This should not be discouraged but it is an opportunity to interrogate the plan and see how this might benefit both the contractor and the supplier.

2) SCHEDULE VARIANCE % (SV):

Schedule Variance % indicates how much ahead or behind schedule the project is in terms of percentage.

Schedule Variance % can be calculated as using the following formula:

· SV % = Schedule Variance (SV) / Earned Value (EV)

· SV % = SV / BCWP

The formula mentioned above gives the variance in terms of percentage which will indicate how much percentage of work is yet to be completed as per schedule or how much percentage of work has been completed over and above the scheduled cost

· Positive Variance % indicates % ahead of schedule

· Negative Variance % indicates % behind of schedule

3) SCHEDULE PERFORMANCE INDICATOR (SPI):

Schedule Performance Indicator is an index showing the efficiency of the time utilized on the project. Schedule Performance Indicator can be calculated using the following formula:

· SPI = Earned Value (EV) /Planned Value (PV)

· SPI = BCWP / BCWS

The formula mentioned above gives the efficiency of the project team in utilizing the time allocated for the project.

· SPI value above 1 indicates project team is very efficient in utilizing the time allocated to the project

· SPI value below 1 indicates project team is less efficient in utilizing the time allocated to the project

4) TO COMPLETE SCHEDULE PERFORMANCE INDICATOR (TSPI):

To Complete Schedule Performance Indicator is an index showing the efficiency at which the remaining time on the project should be utilized. This can be claulated using the following formula:

· TSPI = ( Total Budget - EV ) / ( Total Budget - PV )

· TSPI = ( Total Budget - BCWP ) / ( Total Budget - BCWS )

The formula mentioned above gives the efficiency at which the project team should utilize the remaining time allocated for the project.

· TSPI value above 1 indicates project team can be lenient in utilizing the remaining time allocated to the project.

· TSPI value below 1 indicates project team needs to work harder in utilizing the remaining time allocated to the project.

GUIDELINES FOR DETERMINING VARIANCE THRESHOLDS:

Variance thresholds vary from company to company and are based on risk strategies and the management reserves an organization uses, which are typically 10 to 15 percent. Thresholds can also vary from project to project depending on how critical the business objectives are.

Less than 5 percent (low-risk tolerance): Schedule variances less than 5 percent are an early warning for potential problems.

Between 5 and 10 percent (moderate risk): This range requires that we need to take action.

Greater than 10 percent (high risk): Anything greater than 10 percent requires immediate and substantial action.

These guidelines are best for schedule variances on the critical path because they directly affect the finish date. We can set higher thresholds (for instance, adding 5 percent to the values above) for schedule variances on noncritical path tasks. The higher thresholds mean that we don't have to take action as quickly, but we also don't want those tasks to be delayed so long that they affect those on the critical path.

RESOURCE PLANNING, SCHEDULING AND LEVELLING

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For actual implementation of project different resources are required. They include men, machines, money, and also space without which the implementation of any project cannot commence. Men resource includes labours, planners, designers, supervisory staff, etc. Machinery includes different kinds of equipment for various activities. Out of all above except the money and material all other can be used repetitively.

However, most of the times many activities run concurrently with each other and in such cases it may be possible that the total resources needed for completing the work may not be available. So the available resources will have to be used in such a manner that it satisfies the above constraint. It may also be possible that at the planning stage if particular attention is not paid to the availability of resources the needed resources at some level of the project may exceed the demand, which is not desirable. It is therefore, necessary that the alternative ways of using the available resources be decided so that they are allocated at different levels and stages of the project wherever required. This will lead to obtain the best outcome and profit from all the resources.

Resource Planning and Scheduling:

The resources, especially in case of manpower, are limited and it is necessary that the person in charge of execution or the manager to prepare a resource analysis report which may enable him to put to best use the manpower resource at his hand. There are peaks and valleys in the form of required resources in any project and it has to be tried that these peaks and valleys are to be leveled with the help of resource report. e.g: mason or carpenter in civil engineering project or unskilled labour over the complete period has to be known.

The manager has a definite availability of the resources and he has to plan the requirement of the resource over the different period of execution of the project. He has therefore the following information and alternative:

1. The total requirement of resource for the project over its duration as given by histogram.

2. If the available resources are insufficient this will result in delay in completion of the project. He has to decide the best allocation of available resources over the entire period of project so that the completion period of the project is extended by minimum duration.

3. If the project has to be completed in a fixed period how best can be the available resources to be utilized to achieve the goal.

In the above situation it is necessary to have proper resource scheduling to any one of the following objective

If project duration is fixed, to level or smoothen the resource demand in such a manner that peak and valleys in the demand are avoided as far as possible by suitably spacing in different activities and uniform amount / quantity of the resource is made available. Thus the required uniform resource in the form of manpower or any other is made available. It is presumed that unlimited resources are available. This is resource aggregation.
If the availability of the resources is fixed the same should be so judiciously used so as to complete the project in minimum possible duration. This is resources allocation and is necessary when a particular type of resource is in scarcity or is limited.

Resource Leveling:

In resource leveling there is limited availability of resource. However, normally the available resources should not be less than the maximum number or quantity required for any activity of the project. Therefore the activity requiring a maximum resource dictates the method and along with execution of such activity whichever concurrent activity would be executed, they will be utilizing limited resources. Since the requirement of skill labor is more and the availability is less the rescheduling will have to be effected. In this rescheduling it will be tried to shift first the non critical activities suitably utilizing the available float. However, even with such shifting the demand for such resources may be exceed with availability and in this case even the critical activity also cannot be completed in their duration and hence the duration will have to be increased to suit the availability of the resources. This is therefore; result in increase in the duration of the project. But the available resources being the constraint on the project there is no other way than to accept this delay in completion of project. As such where the completion date is not to be conformed strictly or where there is not likely to the major loss because of some delay in completion of the project and there is availability of limited resources, resource leveling will have to be adopted.

Resource leveling is also a process of trial and mathematical complexity is involved in complex projects having many activities. No technique have been involved as yet to give a optimum solution to such resource leveling problem in straight forward solution can not be obtained. It is only by trial one can come to a conclusion to the problem of resource leveling. Mathematically it is not possible to arrive at a unique solution of minimizing the maximum resources for the project. Manager’s experience in such problems will only help in bringing out and acceptable and practicable solution for resource leveling.

Generally, there are two approaches to leveling and smoothing the resources required:

· Time-limited resource considerations
In this case emphasis will be placed on completing the project within a specified time. This time will usually have been determined by network analysis. Adjustments in the timing of any activity, and the resources required at a given time, must be undertaken within the float (slack) available. Obviously there can be no adjustment of activities which are on the critical path.

· Resource-limited resource considerations
In this case the project must be completed with the resources available even if this means extending the project duration. If the total resource demand exceeds the resource availability at any time then some of the activities must be delayed until there is sufficient resource availability.

TOP DOWN CONSTRUCTION

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Concurrent above and below grade construction

Conventionally, buildings with underground basements are built by bottom-up method where sub-structure and super-structure floors are constructed sequentially from the bottom of the sub-structure or lowest level of basement to the top of the super-structure. Though this conventional method, also called as bottom-up method, is simple in both design and construction, it is not feasible for the gigantic projects with limited construction time and/or with site constraints. Top-down construction method as the name implies, is a construction method, which builds the permanent structure members of the basement along with the excavation from the top to the bottom. Top-down method is mainly used for two types of urban structures, tall buildings with deep basements and underground structures such as car parks, underpasses and subway stations. In this case the basement floors are constructed as the excavation progresses. The top/down method has been used for deep excavation projects where tieback installation was not feasible and soil movements had to be minimized. Top-down construction method which provides the significant saving of the overall construction time has been adopted for some major projects where time factor is of primary importance. The sequence construction begins with retaining wall installation and then load-bearing elements that will carry the future super-structure. The basement columns (typically steel beams) are constructed before any excavation takes place and rest on the load bearing elements. These load bearing elements are typically concrete barrettes constructed under slurry (or caissons).

PROCEDURE

The typical construction procedure of top down construction is as follows

· Construct the retaining wall.

· Construct piles. Place the steel columns or stanchions where the piles are constructed.

· Proceed to the first stage of excavation.

· Cast the floor slab of first basement level

· Begin to construct the superstructure

· Proceed to the second stage of excavation; cast the floor slab of the second basement level.

· Repeat the same procedure till the desired depth is reached

· Construct the foundation slab and ground beams, etc. Complete the basement

· Keep constructing the superstructure till it gets finished.

STRUCTURAL MEMBERS REQUIRED FOR TOP-DOWN CONSTRUCTION

Design and construction principles for top-down method primarily call for two major structural elements.

· Columns with sufficient capacity must be pre-founded in bored piles or barrettes to sustain the construction load and to utilize as part of bracing system.

· Excavation for basement must be carried out with the support of permanent

retaining wall so that basement floor slabs can be utilized as lateral bracing.

Diaphragm wall of 0.8m to 1.2m in thickness with sufficient embedment in firm soil layers is commonly used as a retaining wall whereas prefabricated steel columns known as Stanchions embedded in either large diameter deep-seated bored piles or barrettes are utilized as structural columns. Figure 1 illustrates the top-down construction method with utilization of stanchions and diaphragm wall.

Advantages and disadvantages

Advantages:

1. The shortened construction period due to simultaneous construction of the basement and the superstructure.

2. More operational space gained from the advanced construction of floor slabs.

3. The higher stiffness of floor slab compare to steel struts improves the safety of excavation.

4. It is highly suitable for construction for tall buildings with deep basements to be constructed in urban areas.

Disadvantages:

1. Higher cost (due to the construction of pile foundation)

2. Since the construction period of the basement is lengthened, the lateral displacement of retaining wall or ground settlement may possible increase due to the influence of creep if the soil layers are encountered.

3. The construction quality may influence because of worsened ventilation and illumination under floor slab.

4. It requires highly skilled supervision and labour force.

Conclusion

From the above report we can conclude that top down constuction has its suitability for certain kind of mega structures. It is suitable for structures with deep basements like undergrond rails, car parks etc. It is also very efficient way of doing two way construction to save time. Skyscrapers with deep basements in urban areas should be constucted using top down construction. But top down construction needs very efficient planning and designing and skilled supervision and labour force. Top down construction is the need of the hour as it is highly time efficient and is becoming popular and is coming more and more in practice with every passing day.

VARIOUS TYPES OF FLOOR FINISHES IN

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DEFINITION OF FLOORS:

Floors are horizontal elements of building structures which divide building into different levels for the purpose of creating more accommodation with in the restricted space, one above the other and also provide support to the occupants, furniture and equipments of a building.

FLOOR FINISHES

A floor finish is a liquid which is applied to a resilient tile floor and dries to a hard, durable and smooth film. This film is about the thickness of waxed paper and is expected to protect and extend the life of the floor while providing an attractive appearance and slip resistant surface.

WHAT’S IN A FLOOR FINISH

High quality floor finishes may contain as many as twenty-five ingredients. Some of these ingredients evaporate while others remain on the floor after drying. The ingredients that evaporate are called, "volatile" components and the ingredients that stay on the floor are called, "non-volatile" components. The volatile ingredients assist in the film formation, drying and curing of the finish and then evaporate. The non-volatile ingredients are the solid materials which stay on the floor and make up the floor finish film.

The ingredients used to make floor finishes combine to produce a balanced blend of physical and performance characteristics. Some of these characteristics include: hardness, gloss, clarity, scuff resistance, slip resistance, water and detergent resistance, buffability, removability, recoatability, and toughness.

There are five basic categories of floor finish ingredients, (1) polymer emulsions, (2) film formers, (3) modifiers, (4) preservatives and (5) water.

CRITERIA FOR SELECTION OF FLOORING

• It should be durable

• It should be easy to clean

• Noiseless

• Have Good Appearance

• Free from dampness

• Fire Resistant

• Low Maintenance cost

OPERATIONS REQUIRED BEFORE TAKING UP FLOORING WORK

• Laying of all services like cables, pipes, conduits should be completed

• Plastering works should be completed.

• Fixing of door and window frame should be completed.

• Heavy work in the room where flooring to be done should be completed.

• Marking of outlets and points of level wherever the slopes in the floors required.

OPERATIONS REQUIRED AFTER TAKING UP FLOORING WORK

Grinding of stone :

• Grinding is the process of making the stone surface levelled and uniform.

• This step removes all ledges, roughness and brings flatness to marble floors. Also, this step can remove the most deepest scratches and stains.

Honing of stone :

• Honing is the process of smoothening the surface.

• This step remove scratches,stains and make more uniform finishes.

Stone looks spectacular again.

Polishing Of Stone :

Polishing is the process of creating a smooth and shiny surface by

using rubbing or a chemical action.

• Polishing gives a mirror like look to Stone surface.

• Polishing protects the stone surface from scuffs and scratches.

• Proper polishing of stone surface increases its durability.

• Fine polishing give a glossy look to the stone surface.

• Polishing adds smoothness to stone’s surface.

• Polishing of stone will diminish the finger prints and smudge.

• Well polished stone is easy to clean and maintain.

• Polishing is the most important tool for beautification of stone.

• Polishing of stone also shield it from permanent stains.

Steps to Polish Stone

• Clean the Stone surface appropriately. Ensure that no stains smear left on it.

• Wipe the stone surface and wait till it gets properly dried.

• Spray the good quality polish on stone surface

• Take a white terry cloth and buff it properly.

• Buffing may be done by machine provided, expert to handle it.

• If observe any blotch then stop buffing for few minutes and then restarts the buffing.

• If the smudging continues, just spray again stone polish and without delay buff it. It will give a stripe free shine.

Types of floor finishes :

1) Natural stone floor finish

a) slate

b) Limestone and Sandstone

c) Granite

d) Marble

e) Mosaic

Slate

· Slate is another form of metamorphic rock that consists of silica alumina and iron oxide.

· It is easily split into layers that provide a rugged rustic look.

· It has good abrasion resistance and high durability if it has been correctly cut.

· It is impervious to water, cold hard and noisy under foot and can be slippery.

· A non-slip variety is available.

· It is difficult to lay as the product is quite brittle and heavy.

· It is usually laid into a bed of cement over concrete.

Limestone and Sandstone

· These are derived from sedimentary rocks; deposits of sediment being laid down under water or air formed these.

· Sandstone comes from deposited sand grains i.e. quartz, pressed and held together by silica, calcium carbonate or other cements.

· Limestone comes from deposited organic origin materials i.e. bones shells and consists mainly of calcium carbonate.

· Limestone is rarely used for floors today as it becomes slippery when it is worn and not all products are hardwearing.

· It is grey or beige in color.

· Sandstone - is used more in outdoor paving than indoor, but looks great in an area that flows to the outdoors such as a conservatory.

· Its irregular natural pattern is its best feature and can range from a grainy timber look to stripes and speckles.

· It is beige, brown, reddish brown, in color and some stones are hardwearing.

Granite

Granite used for steps to a commercial building entry.

· Granite is a form of Igneous Rock, created by the cooling of molten magma.

· It is made up of feldspar quartz and mica.

· This is a luxury floor covering and one that needs careful consideration before specification, as it is an expensive product.

· The floor structure needs consideration, as it is very heavy.

· Once laid, it will last for a very long time, as it is hardwearing and resistant to chemicals.

· It has a timeless look.

· If highly polished it is slippery, but a honed finish provides a more manageable finish.

· It comes in limited colors - black, red, green, grey, blue, pink.

· It is supplied in a slab form and is cold and noisy underfoot. But it looks great!

Marble

· This is a form of metamorphic rock, a combination of igneous and sedimentary rocks undergoing a major change due to extreme influences of heat or pressure.

· It is made up of calcium carbonate; it comes in numerous colors, white, grey, green, ochre, beige and is usually veined.

· It is a hardwearing beautiful product, expensive to purchase and lay as it is heavy and comes in slab form.

· It is cold and noisy underfoot.

· From a designers point of view like granite it has a timeless quality.

Marble used of floor and walls of a hotel bathroom, very stylish.

2) Artificial semi hard floor finishes

a) Linoleum

b) Rubber

c) Cork

d) Flexible vinyl

Linoleum

Linoleum is made up from natural ingredients, linseed oil, ground cork, resin, fillers and pigments. These are baked slowly at high temperatures and pressed onto a jute or Hessian backing.

It is a misunderstood product as in its early form it was thin and brittle but with new production methods and design development it is fast becoming a popular flexible flooring choice. It is available in numerous color combinations and can be plain, patterned or in a marbleized look.

It is warm and quiet underfoot. It requires sealing with a polish as if water penetrates under the surface it will lift. It comes in sheet or tile form and is fixed to the floor with an adhesive.

Rubber

Rubber is made from natural or synthetic rubber, fillers and pigments. It is available in single colors with relief patterns or marbled. It comes in sheet form or tiles cut from sheets. The sheet form is available with foam rubber backing which provides a form of sound insulation. It has good wear properties, is resilient and tough, warm and quiet underfoot. It can be loose laid on concrete.

Cork

Cork is a natural product that comes from the bark of the evergreen oak. It is most commonly available in tiles. These are cut from blocks of granulated cork that has been compressed with binders Cork is a natural product that comes from the bark of the evergreen oak. It is most commonly available in tiles. These are cut from blocks of granulated cork that has been compressed with binders

3) Artificial hard floor finishes

a) Cement Resin

b) Terrazzo

c) Concrete Screeds

d) Epoxy Resin

e) Polyester Resin

f) Polyurethane Resin

Cement Resin

This comprises of cement polyester resin and an aggregate (crushed stone or sand). It can be laid over concrete or a timber base. It provides a hardwearing non-slip surface, which has a slight texture.

Terrazzo

This is a composite material made up of cement and marble aggregate, it is then mixed and poured in situ onto a concrete base. It is then ground waxed and polished. It has a mosaic look. It can also be premade and is available in slabs or tiles. It is very hard wearing, if it is polished or wet it is very slippery. It is a suitable product to be used with under floor heating.

It is very useful in commercial situations i.e. malls and shopping centers as it is very durable and easy to clean.

Over large expanses control joints are required to reduce the risk of cracking. It is expensive but worth it in these situations. It can be used to great effect in design work, using brass strips to define the edges with the use of different colored terrazzo between can be very effective.

Concrete Screeds

These are usually used as a base for other floor finishes. There are many forms, monolithic, laid over the concrete base within a few hours of the base being laid. Bonded - existing concrete base with aggregate exposed has a cement screed laid over it. Unbounded - a cement screed is laid over a plain existing concrete base. Floating - is laid over thermal or sound insulation materials.

Epoxy Resin

Produced by combining epoxide resin, fillers, aggregate and hardener. It can be laid over a cement screed, plywood or other surfaces. It provides a thin hardwearing layer available in numerous colors and textures. It can be made non-slip if required.

Polyester Resin

Produced by combining polyester resin, aggregates, fillers, glass fibers pigments and catalyst. It can be laid over a cement screed or plywood. It is a hardwearing product with a wide color range.

Polyurethane Resin

Produced by combining polyurethane resin and fillers. It can be laid over a cement screed or plywood. It provides a hardwearing non-slip surface available in numerous textures and colors.

All the hard flooring examples above are joint less liquid floor finishes. They start as a liquid form then harden to form the desired finish. Terrazzo and cement screed floors are required to be laid in bays with control joints to reduce the possibility of cracking and shrinkage. The majority of these products are best suited for commercial industrial and institutional applications.

4) FALSE FLOORING :

A FALSE FLOORING IS also called raised floor (also raised flooring) is a type of floor used in office buildings with a high requirement for servicing, such as IT data centers, to carry cables, wiring, electrical supply and sometimes air conditioning or chilled water pipes. Additional structural support and lighting are often provided when a floor is raised enough for a person to crawl or even walk beneath.

This type of floor consists of a gridded metal framework or understructure of adjustable-height legs called pedestals, that provide support for individual floor panels which are usually 2×2 feet or 60×60cm in size. The height of the legs/pedestals is dictated by the volume of cables and other services provided beneath, but typically arranged for a clearance of at least six inches or 15cm.

MATERIALS FOR FALSE FLOORING :

• Steel Clad Particle board with cementitious internal core.

• Carpets

• High Pressure laminates

• Marble stone

To Remove Panels :

• Floor Puller or

• Tile Lifter or

• Suction lifter and

• Hook and Loop Lifter on carpet

FIXING FALSE FLOORING :

STEPS FOR EXECUTING FALSE FLOORING :

• Identify the area where FALSE FLOORING is required to execute.

• Clean the area by removing all loose,liatences etc..

• Floor to be coated with epoxy paint for reducing friction for airflow.

• Floor to be insulated in the case of higher floors since the floor is likely to be very cold and can cause sweating on the ceiling of lower floor causing damage to their false ceiling etc.

• Complete the services works like data cable,Wiring,lighting etc.. Before false flooring work.

• Fix the frame work of false flooring like pedestals etc..

• Fix the panels by using nut and bolts of suitable size.

• Make provision for opens and fix these opens with openable panels provided with hinges.

• Mark the ducts for repairs and maintenance of wires,cables inside the false flooring.

• Before closing the false flooring,prepare a diagram showing the rooting of the cables to enable for quick searching of cable.wires etc..in case of failures.

5) Concrete Floor Finishes

Concrete has a proven record for strength, durability, and cost effectiveness for a variety of applications including floors, walkways

and driveways. Concrete floors are found in a variety of residential settings, from high-rise condominiums, to basements remodeled for extra living space, and to slab-on-grade construction. Interior concrete is commonly covered with carpet, vinyl, or other flooring materials. For exterior surfaces, materials like slate, granite, or brick are preferred to standard concrete when budgets allow.

An increasingly popular alternative to covering concrete is to make the surface both decorative and functional. Concrete can be treated with stains or colorants to create a rich variety of hues and textures, or stamped with patterns to mimic natural

surfaces from marble to wood planks. The resulting floor finishes combine beauty and creativity with the economy, durability, and practicality of concrete.

The life expectancy of concrete slabs far exceed that of flooring materials often used to cover them. Carpeting and vinyl are subject to tears, staining, damage from flooding, and general wear. Persons with allergies may also have concerns about dust or molds that may be harbored in carpet fibers. In addition, many floor coverings need to be replaced every few years.

Decorative finishes can be applied to existing or new slabs. The finish can last the lifetime of the concrete, and are durable, sanitary, and easy to maintain. A wide range of effects is possible. The treatment may be as simple as coloring walkways to match architectural features or blend into the landscape. If the look of natural materials is preferred, a slab might be stamped to create the appearance of slate or granite, complete with subtle color shifts, surface texture, and real grout placed in the formed joints between pavers. A stained and scored surface can imitate terra cotta tile, or present a colorful palette of abstract intersecting shapes .

Below are brief descriptions of several methods used for creating decorative concrete surfaces. None of the materials listed below are paints, which would have a much shorter expected lifespan. Except as noted, the treatments become permanent elements of the concrete slab:

Chemical Staining - Special stains are formulated to chemically react with the concrete's lime content. They lightly etch and bond color into the concrete surface. This method can be used on new or old concrete slabs. However, the results are not always predictable due to lime leaching, weathering, surface texture, or exposure to other chemicals, and results may vary widely from project to project. Mottling that occurs in the stain process can create rich tones and complex, almost translucent textures to mimic granite, marble, or to highlight natural variegations in the concrete. Patches or cracks in existing slabs will not be concealed, but may add character and uniqueness. Skilled artisans can create a wide range of effects using, brushes, mops, sprayers, etc., or by creating patterns with leaves, sawdust, rags, or other inert materials. The full depth of color may not become apparent until waxes or sealers are applied to the surface. This is the most versatile and creative method of coloring concrete.

Scoring - Shallow-cuts can be made in existing concrete surfaces to suggest tile grout lines or simply create geometric designs and patterns to separate colors. Standard circular saws with abrasive masonry blades are used to make cuts no more than 1/8" deep. With tile patterns, borders are incorporated into the design a few inches from walls or other vertical surfaces that would prevent the saw from scoring lines all the way to the edge.

Integrally Colored Concrete - Colorant added to concrete during the mixing process produces uniform tinting throughout the slab and consistent results from batch to batch. The colorant may be in liquid or powder form. For small projects, home centers or concrete-product retailers may carry bottles of liquid colorant which can be added to bags of ready-mix. For larger flatwork projects like foundation slabs, walkways, patios, or driveways, bags of powdered water-reducing color admixtures can be ordered at the mixing plant. Admixtures are used to improve plasticity, workability, and to control set time. When pattern stamps are used, a longer period of workability may be needed to complete the process in large areas. Some manufacturers offer their products in pre-measured disintegrating bags designed to treat particular amounts of concrete. The unopened bags are simply tossed into the mixer with water and aggregate prior to adding cement and sand. When pattern stamping is planned, integral colorants may serve as a base tone that can be modified by color hardeners and release agents to achieve a more mottled natural look.

Colored hardeners - Hardening agents in powder form consist of colored, finely-ground, cementitious aggregates that are sprinkled (or "broadcast") onto freshly placed concrete. Moisture seeps from concrete into the powder to activate and monolithically bond it, creating a denser, harder finished surface. Surface strength may be increased up to 7,500 PSI compared to 3,000 to 4,000 PSI for standard 4" concrete. Because the colorant is concentrated into the top layer, hues can be more intense than integrally colored concrete. For improved surface durability, use of colored hardeners is recommended prior to pattern stamping, or in conjunction with chemical staining to produce brighter or deeper finished colors, but the results may vary slightly from batch to batch.

Colored release agents - Pigmented powder or liquid agents are used with pattern stamps to reduce friction and facilitate their removal from fresh concrete surfaces. Applicators may choose release agent colors that contrast or compliment hardener colors to produce a mottled patina or "antique" look on the patterned surface. Unlike the other methods described here, these pigments do not penetrate the concrete surface and must be protected by sealers or wax finishes.

Sealers and Waxes - Colored materials are available to seal and waterproof concrete surfaces, the final step in any finishing process. Manufacturers offer a broad range of products for different applications, ranging from buffing waxes for interior floors to industrial sealers for high traffic exterior settings. Choosing a matching color wax or sealer for integrally-colored concrete can intensify the hue and add gloss. Clear coatings can bring out the depth and luster of antiquing patinas or variegations from chemical staining. Depending on the how heavily the floor is used, sealers or waxes may need to be periodically renewed or reapplied, but maintenance might be as simple as occasionally mopping with floor wax.

Limitations –

Very hard floor surfaces like tile, granite, or decorative concrete may not appeal to consumers with a preference for softer coverings like carpet or resilient vinyl. Objections may involve warmth underfoot, sound deflection, the likelihood of dropped objects shattering, or the safety of very young children who may crawl or fall on the floor surface. Many people with hard surface floors use area-rugs or runners for walkways, play areas, or aesthetic enhancement, but the additional cost of these items should be added to budget calculations when comparing flooring options.

Representative samples may be difficult to produce in some circumstances, especially when staining an existing slab. Color uniformity often cannot be guaranteed and may vary according to the composition of the concrete. Glue residue from previous floor coverings may be difficult or impossible to remove and can involve additional expense.

Ease of Implementation

Most areas have contractors who are trained and outfitted for pattern stamping and tinting exterior concrete surfaces. Some may advertise their specialties in local phone directories or the home improvement sections of newspapers or magazines. Staining specialists can be more difficult to locate. Some work through urban design centers or commercial referrals. The internet can be a valuable search tool in locating skilled local craftspeople.

6) Wood Flooring :

Wood flooring is a type of flooring made from the timber of hardwoods, or of spruce or hard pine.

Thickness of the hard wood is 19mm,10mm and 8mm.

Hard wood finished with polyurethane that has made of aluminium oxide Also,metal oxides like titanium dioxide is used to finish hard wood for better wear.

Fixing of wood floor:

• Clean the floor thoroughly and ensure there are mimnimum variations in the substrata level.The sub floor should be clean and free from dust. Use a broom or vacuum cleaner. The sub floor should not be washed or exposed to water prior to installation always make sure the floor is fully dry prior to installation.

• Apply the concrete sealer on the floor to ensure the moisture in the substrata does not affect the wood floor.

• Using good quality adhesive fix the wood floor panels from one end of the floor.

• Commence laying the flooring at the corner of the starting wall with the tongue of the first row of boards facing away from the wall.

• Glue the boards at the end joints together.

• Any excess of adhesive should be immediately wiped-off with a clean damp cloth. Wipe dry with a dry cloth to avoid "smearing".

• The first board of the next row is pressed into position and tapped into the other board by using a rubber mallet and a tapping block. Never hit the board directly with the mallet. This will increase the risk of damaging the board.

• Chances are that the last row will be less than the width of the boards – so you will have to cut it along the length of the board.

• Take the expansion gap into account when installing the last row of boards and thus cut the timber to the width of the gap of the last row minus the expansion gap (min. 15 mm for expansion joint) (don't include the tongue in this width).

• Apply the adhesive in the groove and put the boards into place with the spacing bar and wedges using a protective piece between wall and tool and between spacing bar and boards. Place the timber as low on the wall as possible and with the spacing bar force the board into position.

• Do this as many times as necessary to close the gap.

• Remove all the spacing wedges once all boards are glued and fitted and the glue is sufficiently dry (see advice on glue bottle).

• Install the trims by nailing or gluing directly to the perimeter walls or existing skirting. Never attach them directly on the installed floor.

Types of wood floor finishes

1. Oil-modified urethane is generally the most common surface finish and is easy to apply. It is a petroleum base with a blend of synthetic resins, plasticizers and other film forming ingredients that produces a durable surface that is moisture-resistant. It is a solvent-base polyurethane that dries in about eight hours. This type of finish ambers with age and comes in different sheen levels.

2. Moisture-cured urethane is a solvent-base polyurethane that is more durable and more moisture resistant than other surface finishes. Moisture-cure urethane comes in non-yellowing and in ambering types and is generally available in satin or gloss. These finishes are extremely difficult to apply, have a strong odor and are best left to the professional.
Curing of this type of finish is by absorbing minute quantities of moisture vapor from the air, which causes them to dry and harden. The curing process is very dependant on relative humidity.

3. Water-based urethane is a water-borne urethane with a blend of synthetic resins, plasticizers and other film forming ingredients that produces a durable surface that is moisture-resistant. These finishes are clear and non-yellowing and are different sheen levels. They have a milder odor than oil-modified finishes have and they dry in about two to three hours. Water-based urethanes are generally more expensive.

4. Converstion-Varnish Sealers-(Swedish Finishes)- A two-component acid-curing, alcohol-based sealers. Because of their origin (country), conversion varnish sealers are often referred to as Swedish finishes

5. Penetrating Sealers - These sealers are spread on the floor and allowed to penetrate and are solvent based. The excess sealer is removed with rags or buffed in with synthetic or steel wool pads. This type of finish often have a color and can be used to stain and seal the wood floor. Penetrating Oil Sealers are made from tung or linseed oil, with additives improve drying and hardness.

6. Paste Wax- The oldest, and in some ways the best. Wax is the easiest to apply, least expensive, fastest drying, easiest to repair, and with proper care will survive forever. Wax over a penetrating stain, and the system is in the wood so you wear the wood, not the finish. Wax is spread in thin coats for a surface protection after the stain and/or sealer is applied, then buffed to the desired sheen.

7. Varnish- Vinyl-alkyd varnishes have superseded natural varnish made from vegetable oils. This product was commonly used before urethane finishes where introduced.

8. Lacquer - The flammability and incompatibility of this floor finish is NOT a recommended by many manufacturers. This finish should avoided.

9. Shellac - This product (natural shellac) contains wax and is not widely used for top coating in today's wood flooring market. Dewaxed shellac is becoming used more and more for a wood floor sealer.

Construction Updates (basic)

BITUMEN

· PHYSICAL PROPERTIES OF ASPHALT

FLY ASH BRICKS

WATERPROOFING OF BUILDINGS

Basement Waterproofing

PRESTRESSING METHOD IN MULTI-STORIED BUILDING FRAME

METHODS AND SYSTEM OF PRE-STRESSING

Pre-cast Pre-tensioned: -

Procedure of precast pre-tensioned concreting

Pre-cast Post-tensioned: -

TYPES OF POST TENSIONED CONCRETING METHODS

BONDED POST-TENSIONED CONCRETE

UNBONDED POST-TENSIONED CONCRETE

Applications

NEW MATERIALS IN CONSTRUCTION (CONCRETE)

Insulated Concrete Forms

Basic Material Used:

Basic Components of ICF System

Structural Design of ICFs Covered by Prescriptive Method

Types of ICF Systems

Three Major types of ICF Systems are,

1. Screen grid OR Post-and- Beam (1st Generation)

2. Waffle grid (2nd Generation)

3. Flat ICF System (2nd Generation)

Manufacturer of ICF Systems

Tools for Block Installation

Tools for Concrete Pour

Tools for Utility Installation

Materials list

ICF Advantages ……

Concrete Homes save Energy

Comfort and Quiet with Concrete Homes

Greater Strength

Better Fire Protection

Quieter

Reduced Maintenance

Resistant to pests

Resistant to mold

PROJECT SCHEDULE CONTROL

2) SCHEDULE VARIANCE % (SV):

3) SCHEDULE PERFORMANCE INDICATOR (SPI):

4) TO COMPLETE SCHEDULE PERFORMANCE INDICATOR (TSPI):

RESOURCE PLANNING, SCHEDULING AND LEVELLING

TOP DOWN CONSTRUCTION

VARIOUS TYPES OF FLOOR FINISHES IN

5) Concrete Floor Finishes

Types of wood floor finishes

4. Converstion-Varnish Sealers-(Swedish Finishes)- A two-component acid-curing, alcohol-based sealers. Because of their origin (country), conversion varnish sealers are often referred to as Swedish finishes

7. Varnish- Vinyl-alkyd varnishes have superseded natural varnish made from vegetable oils. This product was commonly used before urethane finishes where introduced.

8. Lacquer - The flammability and incompatibility of this floor finish is NOT a recommended by many manufacturers. This finish should avoided.

9. Shellac - This product (natural shellac) contains wax and is not widely used for top coating in today's wood flooring market. Dewaxed shellac is becoming used more and more for a wood floor sealer.

1. Screen grid OR Post-and- Beam (1^st Generation)