civil engineering testing Method

GENERAL REQUIREMENTS FOR CONCRETE VIBRATORS, SCREED BOARD TYPE

noreply@blogger.com (Civil Engineering.com) — Wed, 12 Feb 2020 12:10:00 +0000

GENERAL REQUIREMENTS FOR
CONCRETE VIBRATORS, SCREED BOARD TYPE

SCOPE

This standard lays down the requirements for materials, sizes,

construction, assembly and performance of screed board concrete vibrators,

screed board vibrators operated by pneumatic power are not

covered in this standard.

TERMINOLOGY

For the purpose of this standard, the following definitions shall apply.

Amplitude of Vibration - Maximum displacement of a vibrating.

body from its mean position during vibration. It is usually expressed

as half of its total displacement.

Eccentric Shaft ( Rotor ) - The rotating shaft of the vibrating unit

designed to produce the required frequency and amplitude of vibration.

Anchor - The arrangement provided to give a support to the screed

board when desired.

Frequency of Vibration - Number of complete cycles of vibrations

per minute.

Screed Board ( Tamping Beam or Vibrating Beam ) - The beam to

which the vibrating unit is affixed and which compacts the concrete due

to its vibration.

Tube (Casing ) - Fitting whieh encases the eccentric shaft.

2.7 Vibrating Units - The complete assembly of tube, the eccentric

shaft and its bearings, affixed to the screed board to impart vibrations

to it.

Vibration of Acceleration - The maximum acceleration per cycle of

vibration. It is usually expressed as a multiple of g, the acceleration

due to gravity.

MATERIALS

The eccentric shaft shall be made of carbon steel of Grade 35C8 of

IS : 1570 ( Part 2 )-1979” and shall be tempered and polished

The tube or casing of the vibrating unit and other parts shall

conform to IS : 226 - 19757

The rivet bars shall conform to IS : 1148 - 1982$ or IS : 226- 1975t.

3.4 Spring shall be manufactured from suitable grade of wire conforming

to IS : 4454 ( Part 1 )-19813.

All other materials to be used in construction of the screed board

vibrator shall conform to the relevant Indian Standards.

SIZES

Size Designation - The size of the vibrator is designated by the

*overall length of the screed board expressed in metres. Common sizes

of the vibrators are 3, 4 and 5 m.

The vibrating unit or units shall be rigidly affixed to the screed

‘board so that there is no relative : movement between the vibrating beam

and th-e vibrating unit, during operation. Suitable arrangements shall be

provided- to allow for easy fixing and removal of the vibrating unit from

the screed board. Suitable arrangement shall also be provided for occasional

tightening of the fixing joint between the vibrating unit and~the

screed board which may become necessary during operation.

vibrations of vibrating unit or the vibrating beam are not transferred to

it thereby affecting its life and performance; and the efficiency of the

drive shall be such that there is no significant slippage under full operating

loads. In case of belt drives, multiplev-belt drives should preferably

be used, tensioning device shall be provided to keep the transmitting

medium adequately tensioned during operation.

The vibrating unit or units shall be suitably positioned, generally,

symmetrically with respect to the centre of length of the screed board,

to ensure that the amplitude ,and frequency of the screed board are as

far as possible uniform all along its length.

The vibrating beam shall be rigid enough and vibrating units and

the beam supports shall be so placed as to prevent excessive vibration

( whipping ) of the beam between the positions of vibrating units. The,

weight of the beam and the elasticity of the supports shall be so

proportioned that the vibrations are not damped aut by the supports.

Vibrating Unit - The vibrating unit shall be of totally enclosed

construction and shall be filled with correct amount of lubricant and

properly sealed to protect against the entry of dust and moisture.

The tube or casing of the vibrating unit shall be seamless in

construction and shall be of material as specified in 3.2. The minimum

finished wall thickness of the tube anywhere in its length including the

thickness on the bearing seating shall not be less than 4 mm.

The bearings and the eccentric shaft shall be-so assembled as

to enable the easy removal of the shaft for repairs and replacements.

Suitable arrangements shall be provided for adequate lubrication of

bearings so as to prevent them from being heated excessively-in actual

operations. Such a provision also should take care of prevention of

entry of moisture or cement slurry by providing a one way entry for the

lubricant with the help of valve.

Screed Board - The screed board shall generally be of well-seasoned

hard wood timber of cross-section not less than 75 X 150 mm or any

other suitable material. The width of the screed board in any case

shall not be less than 75 mm. If made of hard wood the screed

board shall be shown with steel plate not less than 1’6 mm thick. The

screed board should be checked periodically against bending of board so

that the vibrated surface does not result in a curve.

Handles - The vibrator shall be provided with two handles, each

suitably mounted on either end of the screed board. Each handle shall

be provided with suitable anti-vibration packings or springs so as to

protect it from direct vibrations of the screed board. The handles and

Anchor - An anchor of suitable design shall be provided at one

end of the screed board, preferably mounted on the handle so as to give

support to the entire unit when required. The anchor shall be designed

to dig into ordinary ground without much difficulty.

PERFORMANCE REQUIREMENTS

Operation Characteristics - The vibrators shall be so designed that

when tested for operational characteristics

provisions given in 6.1.1.

shall comply with the

The requirements given in 6.1.1 shall be

checked on selected samples on the basis of suitable sampling scheme.

Frequency of Vibration Minimum Amplitude

Vibrations/minute mm

3 000 to 3 200 for thickness of 1.5

concrete up to 15 cm

3 000 to 3 200 for thickness of 2.0

concrete from 15 to 25 cm

3 500 to 3 700 1.5

NOTE - In no case frequency less than 3 000 shall be accepted.

Mechanical Efficiency - After continuous running of vibration for

more than 4 hours, the rotor temperature shall not be more than 70°C

and shall be tested in accordance with IS : 6923 - 1973*

Endurance Test - The endurance test shall be in accordance with

IS : 6923 - 1973*.

INSTRUCTION SHEET

An instruction sheet containing instructions relating to installation,

maintenance and lubrication of the vibrator and the prime mover shall

be given.

MARKING

8.1 Each vibrator shall have firmly attached to it a mark plate ‘bearing the

following information:

a) Manufacturer’s name or trade-mark:

bj Vibrator reference number;

cl Type and rating of the power unit to be used;

d Year of manufacture; and

e) Frequency and amplitude.

PILE FOUNDATIONS

noreply@blogger.com (Civil Engineering.com) — Wed, 12 Feb 2020 07:34:00 +0000

DESCRIPTION

This work shall consist of construction of all types of piles for structures in

accordance with the details shown on the drawings and conforming to the requirements of

these Specifications or as directed by the Engineer.

The construction of pile foundations requires a careful choice of the piling

system depending on subsoil conditions and loading characteristics and type of structure.

The permissible limits of total and differential settlements, unsupported length of pile under

scour, impact/entanglement of floating bodies and any other special requirements of project,

are also equally important criteria for selection of the piling system. The method of installing

the piles, including details of the equipment shall be submitted by the Contractor and got

approved from the Engineer before commencement of work.

The work shall be carried out as per IS:2911 except as modified herein.

SUBSURFACE INVESTIGATIONS

The complete subsurface investigations of strata in which pile foundations

are proposed shall be carried out in advance along with in-situ pile tests. For details of

geo-technical subsurface explorations, refer Section 2400 of these Specifications.

Borings should be carried up to sufficient depths so as to ascertain the nature of strata

around the pile shaft and below the pile tip. Depth of boring shall not be less than:

i) 1.5 times estimated length of pile in soil or 15 m below the proposed

founding level

ii) 15 times diameter of pile in ordinary I jOinted rock but minimum 15 m in

such rock

iii) 4 times diameter of pile in hard rock but minimum 3 m in such rock

The subsurface investigations shall adequately define stratification of

substrata including the nature and type of strata, their variation, extent and specific properties.

The investigations shall be adequate for the purpose of selection of appropriate piling system

and for estimating design capacities for different diameters and length of piles.

Pressure meter tests may be used in the case of rock, ground or soil for

direct evaluation of strength and comprehensibility characteristics. Though these tests are of

specialized nature, they are more appropriate for difficult/uncertain substrata and especially

for important projects.

For piles socketed into rock, it is necessary to determine the uni-axial

compressive strength of the rock and its quality.

The investigations shall also include location of ground water table and other parameters

including results of chemical tests showing sulphate and chloride content and any other

deleterious chemical content in soil and/or ground water, likely to affect durability.

TYPE OF PILES

Piles may be of reinforced concrete, prestressed concrete, steel or timber

and circular, square, hexagonal, octagonal, "H" or "I" Section in shape. They may be of solid

or hollow sections or steel cases filled with concrete. Timber piles may be used for temporary

bridges. Cast in-situ concrete piles may be driven cast in-situ or bored cast in-situ. Similarly,

precast concrete piles also may be driven precast or bored precast. In bored precast piles,

precast piles are lowered into pre-formed bores and annular space grouted.

Minimum diameter of concrete pile shall be 1 m for river/marine bridges.

For bridges beyond the water zone and bridges on land, the minimum diameter may be

750 mm.

MATERIALS

The basic materials shall conform to Section 1000 of these Specifications.

The specifications for steel reinforcement, structural concrete, prestressed concrete and

structural steel to be used in pile: foundations shall conform to Sections 1600, 1700, 1800

and 1900 respectively of these Specifications.

Concrete in Piles

For both precast and cast in in-situ piles, the grade of concrete, minimum cement content,

water cement ratio and slump at the time of placement shall be as per Table 1100-1 :

Table 1100-1 : Requirements for Concrete in Piles

Cast in-situ Concrete by Tremie Precast Concrete

Grade of concrete M 35 M 35

Minimum cement content 400 kg/m3 400 kg/m3

Minimum water cement ratio 0.4 0.40

Slump (mm) as measured at the 150-200 50 -75

time of placement

The terms 'minimum cement content' and 'minimum water cement' ratio mentioned

Table 1100-1, are to be based on total cementitious material (inclusive of all mineral admixtures

called additives) mentioned in Clause 1007 of these Specifications. Maximum limits for such

additives shall be as specified in Clause 1716.2 of these Specifications.

Pile Foundations

High alumina cements (i.e. quick setting cement) shall not be used in marine conditions.

When both chlorides and sulphates are present, in soil or ground water, sulphate resistant

cement shall not be used. For improving resistance against the penetration of chlorides and

sulphates from surrounding soils or water, mineral admixtures such as fly ash, silica fumes,

GGSS conforming to respective SIS/International Standards and as per IRC:112, may be

used.

TEST PILES

Test piles which are shown on the drawings or specified in the contract or

installed by the Contractor on his own to determine the lengths of piles to be furnished, shall

conform to the requirements for piling as indicated in these Specifications. Test piles which

are used to arrive at the load carrying capacity shall not be incorporated in the structure.

All test piles shall be installed with the same type of equipment that is proposed to be used

for piling in the actual structure.

Test piles which are not to be incorporated in the completed structure shall be removed to at

least 600 mm below the proposed soffit level of pile cap and the remaining hole so formed

shall be backfilled with earth or other suitable material.

The piles shall be load tested in accordance with provisions laid down in this Section.

PRECAST CONCRETE PILES

Precast cotlcretepiles shall be of the size and shape as shown in the approved drawings.

If a square section is employed, the corners shall be chamfered by at least 25 mm

unless otherwise specified on the drawings. The length of pile shall not normally exceed

25 m. However, where special equipments for handling and installation are available to the

satisfaction of the Engineer, longer length could be permitted.

Stacking, Storing and Handling

Care shall be taken that at all stages of transporting, lifting and handling, the piles are ncit

damaged or cracked. During transport and stacking of piles, they shall be supported at the

same points as those provided for lifting purposes. If the piles are put down temporarily

during handling, they shall be placed on trestles or blocks located at the same points.

Piles shall be stored at least 300 mm above firm level ground, which is not liable to unequal

subsidence or settlement under the weight of the stack of piles. They shall be placed on

timber supports which are level and spaced so as to avoid bending. The supports in different

layers, shall be vertically one above the other. Spaces shall be left round the piles to enable

them to be lifted without difficulty. The order of stacking shall be such that the older piles can

be withdrawn without disturbing newer piles. Separate stacks shall be provided for different

lengths of piles. Where piles are stacked in layers, the number of layers shall not exceed

three. Whenever curing is needed during storage, arrangements shall be made to enable the

piles to be watered. For detailed precautions with regard to curing operations for structural

concrete, refer Section 1700 of these Specifications.

Before the operation of handling and driving the piles, the minimum periods counted from the

time of casting shall be as indicated in Table 1100-2. Prestressed pile shall not be lifted or

handled until fully stressed.

Table 1100-2 : Time for Curing Precast Piles

Type of Cement Used Minimum Periods from Time of Casting

in Casting the Pile

Strike Side- End of Wet Lift from Bed Casting Drive

Shutters (Hours) Curing (Days) (Days) (days)

Ordinary Portland 24 7 10 28

Rapid hardening 12 7 7 10

Portland

Lengthening of Piles

Where a pile is to have additional length cast on it during driving, the longitudinal reinforcement

shall preferably be joined by full penetration butt welding. The concrete at the top of the

original pile shall be cut down to expose not less than 200 mm of the bars to avoid spalling

of the concrete by heat of welding. The added bars have to be held accurately and rigidly in

position during welding. Where facilities on site are insufficient to make proper butt welding

practicable, the joint may be made by lapping. The reinforcement at the head of pile will need

to be exposed for full anchorage length or 600 mm whichever is greater and the new bars

over-lapped for this distance. Unless otherwise specified, the extension of the pile shall be

formed to the same cross-sectional profile and with concrete of at least the same strength

as that specified for the original pile. The stirrup spacing shall in no case be £Ireater than

150 mm. Not more than one extension shall be permitted. In case more than one extension

is permitted by the Engineer, only approved mechanical couplers shall be used.

Driving shall not be resumed until:

a) The strength of the concrete in the extension is at least equal to the

specified characteristic strength of concrete in pile; and

b) The approval of the Engineer has been obtained.

Removal of Surplus Length

Any length of pile surplus to that required for incorporation in the structure shall be cut off

neatly and removed. During the process of cutting off, it shall be ensured that projecting

reinforcement to be anchored into the pile cap and the prestressing strands/wires are not

damaged. When stripping prestressed concrete piles, sudden release of tendons shall be

avoided. Reference may also be made to Clause 7.7.1 of IS:2911 (Part I, Section 3) in this

connection.

Risen Piles

Level of top of each pile shall be taken after driving and again after all the piles are driven.

Piles which are found to have risen due to ground heave or as a result of driving adjacent

piles, shall be re-driven to the original depth or resistance unless re-driving tests on adjacent

piles have shown this to be unnecessary.

Manufacture

The pile should be cast in one continuous operation from end to end of each pile. Manufacture

of precast concrete piles shall conform to the guidelines contained in Clause 7.1, 7.2

and 7.3. or IS:2911 (Part I, Section 3).

Piles shall be provided with suitable metal shoe for protecting the tip of the pile during driving

in hard ground.

Piles shall not be moved from casting bed until the concrete has hardened sufficiently.

Piles shall not be driven in less than 28 days after casting or unless their strength at the time

of driving is at least that specified for 28 days.

Prestressed Concrete Piles

Additional specifications for precast prestressed concrete piles shall conform to those

contained in Clause 8 of IS:2911 (Part I, Section 3).

CAST IN-SITU CONCRETE PILES

General

Cast in-situ concrete piles may be either installed by drilling a bore into the ground and

removing the material or by driving a metal casing with a shoe at the tip and displacing

the material laterally. The two types of piles are termed as "bored piles" and "driven piles"

respectively. Cast in-situ concrete piles may be cast in metal shells which may remain

permanently in place. However, other types of reinforced concrete cast in-situ piles, cased

or uncased, may be used if in the opinion of the Engineer the soil conditions permit their use

and if their design and the methods of placing are satisfactory.

Certain specific requirements regarding driving of cast in-situ driven piles shall be as per

Clauses 1110 and 1111.

Any liner or borehole which is improperly located or shows partial collapses that would affect

the load carrying capacity of the pile, shall be rejected or repaired as directed by the Engineer

at the cost of the Contractor.

Boring shall be carried out using rotary equipment. Percussion type of equipment shall be

used only if approved by the Engineer.

The diameter of the finished pile shall not be less than that specified. A continuous record

shall be kept by the Engineer as to the volume of concrete placed in relation to the length of

pile that is cast.

Defective piles shall be removed or left in place as judged convenient without affecting the

performance of adjacent piles or pile cap. Additional piles shall be provided to replace the

defective piles.

Concreting

Wherever practicable, concrete should be placed in a clean dry hole. Prior to the placing of

the reinforcement cage, the pile shaft shall be cleaned of all loose materials. Before concreting

of the pile is commenced, it is essential to ensure that no debris remains at the bottom of

the shaft, as inadequate cleaning of the base can lead to formation of a soft base or soft toe

which may result in reduction of load bearing capacity of the pile.

Reinforcement for the pile as shown on the drawing shall be tied in place to form a cage which

is lowered into the pile shaft. Suitable spacers shall be provided to maintain the required

cover to reinforcing steel. Reinforcements at the bottom should not be provided with L-bends

as these may interfere with cleaning of the pile base.

Where concrete is placed in dry and a casing is present, the top 3 m of the pile shall be

compacted using internal vibrators.

Where the casing is withdrawn from cohesive soils for the formation of cast in-situ pile, the

concreting should be done with necessary precautions to minimize the softening of the soil

by excess water. Where mud flow conditions exist, the casing of cast in-situ piles shall not

be allowed to be withdrawn.

Care shall be taken during concreting to prevent the segregation of the ingredients. The

displacement or distortion of reinforcement during concreting and while extracting the casing,

shall also be avoided.

If the concrete is placed inside precast concrete tubes or consists of precast sections, these

shall be free from cracks or other damage before being installed.

The concrete shall b~ properly graded, shall be self-compacting and shall not get mixed with

soil, excess water, or other extraneous matter. Special care shall be taken in silty clays and

other soils which have the tendency to squeeze into the newly deposited concrete and cause

necking. Sufficient head of green concrete shall be maintained to prevent inflow of soil or

water into the concrete.

The placing of concrete shall be a continuous process from the toe level to the top of the pile.

To ensure compaction by hydraulic static heads, rate of placing concrete in the pile shaft shall

not be less than 6 m (length of pile) per hour.

Casing

When concreting is carried out for a pile, a temporary casing should be installed to sufficient

depth so as to ensure that fragments of soil from the sides of the hole do not drop into the

concrete as it is placed. When the bore hole is stabilized using drilling mud, the temporary

casing is not required except near the top.

The metal casing shall be of sufficient thickness and strength to hold its original form and

show no harmful distortion while driving or when adjacent casings are driven.

Cast in-situ concrete driven piles shall be installed using a properly designed detachable

shoe at the bottom of the casing.

Bored cast in-situ piles in soils which are stable, may often be installed with only a small

casing length at the top. A minimum of 2 m length of top of bore shall invariably be provided

with casing to ensure against loose soil falling into the bore. In cases in which the side soil

can fall into the hole, it is necessary to stabilize the side of the bore hole with drilling mud, or

a suitable steel casing. Permanent steel liner shall be provided at least up to maximum scour

level. The minimum thickness of steel liner shall be 6 mm.

Permanent steel liner shall be provided for the full depth of the pile in the following situations

where:

i) The surrounding soil is marine clay

ii) Soft soil is present

iii) Surrounding soil has sulphate content equal to or more than 1 %

iv) Surrounding water has sulphate content equal to or more than

2500 ppm

v) Leakage of sewage is expected

For bored cast in-situ piles, casing/liner shall be driven open ended with a pile driving hammer

capable of achieving penetration of the liner to the depth shown on the drawing or as approved

by the Engineer. Materials inside the casing shall be removed progressively by air lift, grab

or percussion equipment or other approved means.

Where bored cast in-situ piles are used in soils liable to flow, the bottom of the casing shall

be kept sufficiently in advance of the boring tool to prevent the entry of soil into the casing,

leading to formation of cavities and settlements in the adjoining ground. The water level in

the casing should generally be maintained at the natural ground water level for the same

reasons. The joints of the casing shall be made as leak-tight as possible torilinimize inflow

of water or leakage of slurry during concreting.

The diameter of the boreholes shall not be more than the inside diameter of the liner when the

liners are installed before boring. When the liners are installed after boring, the diameter of

the boreholes shall not be more than the outside diameter of liner + 2 mm, unless otherwise

approved by Engineer.

Use of Tremie

The concrete should invariably be poured through a tremie with a funnel, so that the concrete

can be properly deposited in the hole without segregation. For concreting done by tremie, the

following requirements which are particularly applicable shall be ensured:

a) The hopper and tremie should be a leak proof system.

b) Diameter of tremie shall be not less than 200 mm for use with 20 mm

diameter down aggregate.

c) The first charge of concrete should be placed with a sliding plug pushed

down the tube ahead of it or with a steel plate with adequate charge to

prevent mixing of concrete and water. However, the plug should not be

left in the concrete as a lump.

d) The tremie pipe should always penetrate well into the concrete with an

adequate margin of safety against accidental withdrawal of the pipe.

The tremie should be always full of concrete.

e) The pile should be concreted wholly by tremie and the method of

deposition should not be changed part way up the pile, to prevent

laitance from being entrapped within the pile.

f) All tremie tubes shall be thoroughly cleaned after use.

g) For concrete placed through tremie, there is no need to add 10 percent

extra cement.

h) Concreting of piles shall be carried out continuously. In exceptional

cases of interruption of concreting the tremie shall not be taken out of

the concrete under any circumstances. The tremie pipe shall be raised

and lowered slowly from time to time to prevent it from getting stuck in

the concrete while ensuring its lower and does not come out of concrete.

The concreting shall be resumed before final setting time of concrete,

which shall be established before the start of the piling qperation. For

achieving longer setting time of the concrete, super plasticizers having

retarding properties/retarders can be used. Ifany of these requirements

are not met, the pile shall be rejected.

Removal of Concrete above Cut-off Level

It is desirable that the concrete above cut-off level, is removed before the concrete is set.

This may be done manually or by specially made bailer or other device. Such removal of

concrete helps in preventing the damage of the good concrete below the cut-off level, which

results from chipping by percussion method.

The removal of concrete shall be within ± 25 mm from the specified cut off level, preferably

on the minus side. After removal of such concrete, the concrete shall be compacted with

rammer with spikes or vibrated.

In case the concrete is not removed before setting, a groove shall be made on outer perimeter

by rotary equipment before chipping by percussion method.

The minimum embedment of cast in-situ concrete piles into pile cap shall. not be less then

50 mm. Any defective concrete at the head of the completed pile shall be cut away and

made good with new concrete. The clear cover between the bottom reinforcement in pile

cap from the top of the pile shall be not less than 25 mm. The reinforcement in the pile shall

be exposed for full anchorage length to permit it to be adequately bonded into the pile cap.

Exposing such length shall be done carefully to avoid damaging the rest of the pile.

STEEL PILES

Steel piles shall be of "H" or "I" sections as shown on the drawings and shall be of structural

steel conforming to Section 1 000 of these Specifications.

Steel piles shall be protected by suitable anti-corrosive painting as specified on the drawing

or as directed by the Engineer. Piles shall be stored above the ground having protective

packing to minimize damage to surface coating. Each pile shall be supplied preferably in one

piece without splices.

At the option of the Contractor, steel piles consisting of structural steel plates welded together

may be substituted for the rolled sections specified, provided the depth, width and average

thicknesses are at least equal to those of the rolled sections, the steel plates conform to

Section 1000 of these Specifications. The flanges shall be welded to the web with continuous

fillet welds on either side of the web, and the welding shall conform to Clause 1904.8 of these

Specifications.

The length of the steel pile may be built up in sections either before or during driving

operations. The sections shall be of identical cross-section. Pile splices shall be made with

.. full penetration butt welds over the whole cross-section. Pile splices shall develop at least

the yield strength of pile.

The connections shall be made by butt welding the entire cross-section in accordance with

the provisions in Clause 1904.8 of these Specifications. Care shall be taken to properly align

the sections connected so that the axis of the pile will be straight. The number of welded

connections in the length of pile shall be as few as possible.

TIMBER PILES

The Engineer shall stamp each pile on the butt with a stamp which shall make an impression

that is readily legible. Treated timber piles will be inspected by the Engineer after treatment.

Untreated timber piles may be used as test piles. Treated timber piles shall be driven within

6 months after treatment.

Timber piles shall be furnished with tip protection and protected by the use of steel straps.

Tip protection shall be suitable for use on timber piling of the size to be driven. Details of tip

protection shall be furnished to the Engineer for review and approval before driving piles. Not

less than 2 separate steel straps shall be placed within 600 mm of the butt of each pile after

the pile is square cut. Not less than 2 separate steel straps shall be placed within 300 mm

of the tip of each pile. Additional intermediate steel straps shall be placed at intervals of not

more than 3 m measured along the length of the pile.

Timber piles which are to be capped shall be separately cut off so that true bearing is obtained

on every pile. Piles inaccurately cut off shall be replaced. Splicing of timer piles shall not be

permitted except by written permission of the Engineer.

DRIVING EQUIPMENT

Piles or their casings may be driven with any type of drop hammer, diesel hammer or singleacting

steam or compressed air hammer, provided they penetrate to the prescribed depth to

attain the designed resistance without being damaged. The weight or power of the hammer

should be sufficient to ensure a penetration of at least 5 mrn per blow unless rock has been

reached. It is always preferable to employ the heaviest hammer practicable and to limit the

stroke, so as not to damage the pile. The minimum weight of the hammer shall be 2.5t. In

the case of precast concrete piles the mass of the hammer shall be not less than 30 times

the mass of 300 mm length of pile.

Steam or air hammers shall be furnished along with boiler or air compressor of capacity at

least equal to that specified by the manufacturer of the hammers. The boiler or air compressor

shall be equipped with an accurate pressure gauge at all times. The valve mechanism and

other parts of steam, air or diesel hammers shall be maintained in first class condition so that

the length of stroke and number of blows per minute for which the hammer is designed, will

be obtained. Inefficient steam, air or diesel hammers shall not be permitted to be used on

the work.

DRIVING

General Procedure

Details of the equipment and the method proposed for driving the piles shall be submitted

for scrutiny and approval of the Engineer. Piles shall be installed from firm ground or from

temporary supports or from fixed platform. The arrangement shall provide sufficient rigidity

to ensure accuracy of pile driving under all conditions of tide, stream flow or hammer drop.

During driving the top of pile shall be protected by a suitable helmet of substantial steel

construction. The helmet shall provide uniform bearing across the top of the pile and shall

hold the pile centrally under the hammer. No pile shall be driven unless inspected and

approved by the Engineer.

Piles shall be driven from a fixed frame of sufficient rigidity to ensure accuracy of driving

within specified tolerances. The force of the hammer shall be directed centrally and axially

during driving. Forces producing undue bending or torsional stresses in piles shall not be

applied during driving.

The stroke of a single acting or drop hammer shall be limited to 1.2 m unless otherwise

permitted by the Engineer. A shorter stroke may be necessary when there is danger of

damaging the pile.

Piles shall not be bent or sprung into position but shall be effectively guided and held on line

during the initial stages of driving. Attempts to correct any tendency for the pile to run off line

by the application of significant horizontal restraint will not be permitted. Shortly after the

commencement of driving and at regular intervals throughout the driving operation, checks

shall be made to ensure that the pile frame does not exert any undue lateral force on the pile

due to restraint within the helmet.

If the indications are that a pile will finish outside the specified tolerances, driving operations

on that pile will cease. The pile shall be withdrawn, the hole filled and the pile re-driven at

the cost of the Contractor.

To avoid the possibility of premature "set-up", pile driving shall be continuous in the later

stages, without any deliberate stops. (delays of an hour or less may lead to significant "setup"

in piles i.e. resistance to further driving increases after driving is stopped).

If any pile is damaged in any way during driving, it shall be repaired or replaced as directed by

the Engineer, at the cost of the Contractor. If during driving, the head of a pile is damaged to

the extent that further driving is not possible, the head shall be cut off and driving continued.

The cost of cutting off shall be borne by the Contractor and where, as a result of such cutting

off the head, the pile is too short, the Contractor, shall, at his own cost, supply and splice on

sufficient length of pile to restore the pile to its correct length.

Piles should be driven to the minimum acceptable penetration shown on the drawings. This

may require pre-boring and/or jetting as indicated in Clause 111.2, with the approval of the

Engineer.

Piles shall be driven to nominal refusal or the required ultimate dynamic capacity mentioned

on the drawings or until the top of the pile is at the level required and specified on the drawing

whichever gives the lowest toe elevation. The Engineer's decision in these matters shall be

final. Nominal refusal shall be taken as equivalent to 25 mm total penetration for the final

20 blows using a hammer of driving energy as specified and shall be used as the criterion

for acceptance for piles founded on rock. Severe driving which results in an average set per

blow less than 0.5 mm will not be permitted.

Where hard drilling is encountered because of dense strata or obstructions located above the

predetermined pile tip level, nominal refusal shall not be considered to have been achieved

unless the Engineer is satisfied that the total number of blows, as the average driving

resistance specified for nominal refusal, indicates that further driving will not advance the pile

through dense strata or obstructions.

The pile shall be driven as accurately as possible to the vertical or to specified batter. Straining

the pile into position can damage it and the driving equipment should be adjusted as much

as possible to follow the position of the pile. Any deviation from the proper alignment shall

be noted and promptly reported to the Engineer. If the deviation is to such an extent that the

resulting eccentricity cannot be taken care of by strengthening the pile cap or pile tips, such

a pile shall, at the discretion of the Engineer, be replaced or supplemented by an additional

pile. Unless otherwise specified, the permissible positional deviation for piles shall be limited

to those indicated in Clause 1116.

Care shall be taken not to damage the pile by over-driving. Any sudden change in the. rate of

penetration which cannot be ascribed in the nature of the ground shall be noted and its cause

ascertained, if possible, before driving is continued.

While withdrawing a casing used in the construction of cast in-situ pile, consideration shall be

given to the possibility of damaging any other nearby pile. The danger of damaging is greater

in compact soils than in loose soils. No pile shall be bored or driven within 3 m of a newly

cast pile until at least 24 hours after completion of its installation.

Driving piles in loose sand tends to compact the sand which in turn increases the skin friction.

Therefore, driving a number of friction piles in a group shall proceed outward from the centre

as otherwise it will be difficult to drive the inner piles to the same depth as the others.

In the case of stiff clay also, the driving for a group of piles shall proceed outward from the

centre. However, in case of very soft soil, the driving may proceed from outside to inside, so

that the soil is restrained from flowing out during driving operations.

If there is a major variation between the depth at which adjacent foundation piles in a group

meet refusal, a boring shall be made nearby to ascertain the cause of this difference. If the

boring shows that the soil contains pockets of highly compressive material below the level of

the shorter pile, it will be necessary to enforce penetration of all the piles to a level below the

bottom of the zone which shows such pockets.

Pre-boring and Jetting

Driving of the piles may be assisted by pre-boring holes or by the use of jets or both, subject

to the approval of the Engineer. These may be used essentially to achieve the minimum

penetration shown on the drawings where such penetration is not reached under normal

conditions of driving indicated in Clause 1111.1.

The diameter of the hole shall not be greater than the diagonal dimension of the pile less

100 mm.

The maximum depth of the pre-boring shall be such that the specified set (or less) is obtained

when the toe of the pile is at founding level. Pre-boring shall be as approved by the Engineer

and shall be carried out only up to a level of one metre above the founding level. The pile

shall be driven for at least one metre below the pre-bored hole. To ensure that the pile is

properly supported laterally in the hole, any space remaining around the pile at the ground

level after driving is completed, shall be backfilled with approved granular material.

When water jetting is used, at least two jets shall be attached to the pile symmetrically. The

volume and pressure of water at the outlet nozzles shall be sufficient to freely erode material

adjacent to the toe of the pile. The maximum depth up to which jetting is carried out, shall be

such that the specified set (or less) is obtained when the toe of the pile is at founding level.

Jetting shall cease as directed by the Engineer and shall proceed only up to 1 m above the

founding level. The pile shall be driven at least 1 m below the pre-bored hole.

To avoid very hard driving and vibration in materials such as sand, jetting of piles by means

of water may be carried out only with the express permission of the Engineer and in such a

manner as not to impair the bearing capacity of piles already in place, the stability of the soil

or the safety of any adjoining buildings. Details of the arrangement for jetting shall be got

approved from the Engineer in advance.

If large quantities of water are used for jetting, provision shall be made for collecting and

draining away of water when it comes to the surface of the ground, so that the stability of the

piling plant is not endangered by the softening of the ground.

Jetting shall be stopped before completing the driving which shall always be finished by

ordinary methods. Jetting shall be stopped if there is any tendency for the pile tips to be

drawn towards the pile already driven owing to the disturbance of the ground.

TEN PERCENT FINES VALUE.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:48:00 +0000

TEN PERCENT FINES VALUE.

( BS : 812 – PART – 111 )

INTRODUCTION:

The ‘Ten percent fines’ value is a measure of resistance of the aggregates to the crushing.

Object:

To determine the ten percent value of aggregates by crushing machine apparatus.

Apparatus:

a) Steel cylinder with open ends, and internal diameter 152mm, square base plate, plunger having a piston of diameter 150mm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder.

b) Cylindrical measure having internal diameter of 115mm and height 180mm.

c) Steel tamping rod with one rounded end, having a diameter of 16mm and length 450 to 600mm.

d) Balance of capacity 3 kg with accuracy up to 1gm.

e) Compressive testing machine capable of applying load of 40 tonnes, at a uniform rate of loading of 4 tonnes per minute.

Procedure:

The aggregate passing 14mm IS sieve and retained on 10mm IS sieve is selected for test. The aggregate should be in surface-dry condition before testing. The aggregate may be dried by heating at a temperature 100⁰C to 110⁰C for a period of 4 hours and is tested after being cooled to room temperature.

The cylindrical measure is filled by the test sample of aggregate in three layers of approximately equal depth, each layer being tamped 25 times. The same sample poured in to the cylinder with three equal layers, each layer being tamped 25 times. The test sample in the cylinder with the plunger in position is placed in the compression-testing machine. The load is applied at a uniform rate so as to cause a total penetration of the plunger of about 20mm for normal crushed aggregates in 10 minutes. But for rounded or partially rounded aggregates, the load required to cause a total penetration of 15mm is applied where as for honeycombed aggregate like expanded shale or slag that for a total penetration of 24mm is applied in 10 minutes. After the maximum specified penetration is reached, the load is released and the aggregate from the cylinder is sieved on a 2.36mm IS sieve. The fines’ passing this sieve is weighed and is expressed as a percentage by weight of the test sample. This percentage normally falls in the range of 7.5 to 12.5;

but if it does not fall in this range, the test is repeated with necessary adjustment of the load.

Two tests are carried out at the load ‘X tonnes’, which give the percentage fines between 7.5 to 12.5 and let the mean of the percent fines be ‘Y’ for calculating the load required for ten percent fines.

14 X

Load for 10 percent fines =

(Y + 4)

Results:

The 10 percent fines value of Granular Sub base material is should be more than 50 KN.

STRIPPING VALUE OF AGGREGATES.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:48:00 +0000

STRIPPING VALUE OF AGGREGATES.

(IS: 6241 – 1959)

INTRODUCTION:

Bitumen and tar adhere well to all normal types of aggregates provided they are dry and are not exceptionally dusty. Largely the viscosity of the binder controls the process of binding. When the viscosity of the binder is high, coating of aggregates by the binder is slower. In the absence of water there is practically no adhesion problem in bituminous road construction. Two problems are observed due to the presence of water. First, if aggregate is wet and cool it is normally not possible to coat with a bituminous binder. This problem can be dealt with by removing the water film on aggregate by drying, and by increasing the mixing temperature. Second problem is stripping of coated binder from the aggregate due to the presence of water. This problem of stripping is experienced only with bituminous mixtures, which are permeable to water.

Object:

To determine the stripping value of aggregates by static immersion method.

Apparatus:

Thermostatically controlled water bath, beaker.

Procedure:

This method covers the procedure for determining the stripping value of aggregates by static immersion method, when bitumen and tar binder are used. 200gm of dry and clean aggregates passing 20mm IS sieve and retained on 12.5mm sieve are heated up to 150⁰C when these are to be mixed with bitumen and the aggregates are heated up to 100⁰C when these are to be mixed with tar. 5% by weight of bitumen / tar binder is heated to 160⁰C (110⁰C in the case of tar binder). The aggregate and binder are mixed thoroughly till they are completely coated and the mixture is transferred to a beaker and allowed to cool 500ml at room temperature for about two hours. Distilled water is then added to immerse the coated aggregates. The beaker is covered and kept in a water bath maintained at 40⁰C, taking care that the level of water in the water bath is at least half the height of the beaker. After 24 hours the beaker is taken out, cooled at room temperature and the extent of stripping is estimated visually while the specimen is still under water.

The stripping value is the ratio of the uncovered area observed visually to the total area of aggregates in each test, expressed as a percentage.

Limits: The maximum stripping value is 5 %( i.e., minimum retained coating is 95%).

SPECIFIC GRAVITY TEST.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:47:00 +0000

SPECIFIC GRAVITY TEST.

( IS : 1202 – 1978 )

Object:

To determine the specific gravity of the bitumen by specific gravity bottle.

Apparatus:

a) Pycnometer / specific gravity bottle – 50 ml capacity.

b) Balance – sensitivity 0.1mg.

Procedure:

The specific gravity bottle is cleaned, dried and weighed along with the stopper. It is filled with fresh distilled water, stopper placed and the same is kept in water container for at least half an hour at temperature 27⁰C +/- 1⁰C. The bottle is then removed and cleaned from outside. The specific gravity bottle containing distilled water is now weighed.

The bituminous material is heated to a pouring temperature and is poured in the above empty bottle taking all the precautions that it is clean and dry before filling sample materials. The material is filled up to the half taking care to prevent entry of air bubbles. To permit an escape of air bubbles, the sample bottle is allowed to stand for half an hour at suitable temperature cooled to 27⁰C and then weighed. The remaining space in the specific gravity bottle is filled with distilled water at 27⁰C, stopper placed and is placed in water container at 27⁰C. The bottle containing bituminous material and remaining water is removed, cleaned from outside and is again weighed.

Calculations:

The specific gravity of the bituminous material is calculated as follows:

Weight of bituminous material ( c – a )

Specific gravity = =

Weight of equal volume of water at 27⁰C (b – a) – (d – c)

Where a = weight of the specific gravity bottle

b = weight of the sp.gravity bottle filled with distilled water.

c = weight of the sp.gravity bottle about half filled with bitumen.

d = weight of the sp.gravity bottle about half filled with bitumen and

the distilled water.

Limits: Specific gravity of Bitumen at 27⁰C is Minimum 0.99.

SPECIFIC GRAVITY TEST FOR SOILS.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:46:00 +0000

SPECIFIC GRAVITY TEST FOR SOILS.

( IS : 2720 – PART – 3 )

Object:

To determine the specific gravity of soil fraction passing 4.75 mm sieve by density bottle.

Apparatus:

1) Density bottle of 50ml / 100ml capacity.

2) Balance sensitive to 0.01g.

3) Wash bottle with deaired distilled water

4) Vacuum source

Procedure:

To clean and dry the density bottle, wash it thoroughly with distilled water and allow it to drain. Weigh the empty cleaned bottle (W1) accurate to 0.01g with its stopper. Take about 10 to 20 grams of oven dried soil sample; find the weight (W2) of the bottle and the soil, with the stopper. Put about 10ml of deaired distilled water in the bottle, so that the soil is fully soaked. Leave it for a period of 2 to 10 hours. Add more distilled water so that the bottle is about half full. Remove the entrapped air by subjecting the contents to a partial vacuum, then find out the weight (W3). Clean the bottle thoroughly and fill it with distilled water and weighed (W4). Temperature should be maintained 27⁰C through out the test.

Calculations:

(W2 – W1)

Specific gravity of the soil = G =

(W2 – W1) – (W3 – W4)

Where, W1 = weight of the empty bottle with stopper.

W2 = weight of the bottle + Soil sample with stopper.

W3 = weight of the bottle + sample + water with stopper.

W4 = weight of the bottle + water with stopper.

DETERMINATION OF SPECIFIC GRAVITY OF CEMENT.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:46:00 +0000

DETERMINATION OF SPECIFIC GRAVITY OF CEMENT.

( IS : 2720 – Part – 3 )

Object: To determine the specific gravity of cement using Le Chatelier Flask or Spcefic Gravity Bottle.

Apparatus:

a) Le Chatelier Flask or Specific Gravity Bottle – 100 ml capacity.

b) Balance capable of weighing accurately upto 0.1gm.

Procedure:

Weigh a clean and dry Le Chatelier Flask or Specific Gravity Bottle with its stopper (W1). Place a sample of cement upto half of the flask (about 50 gm) and weight with its stopper (W2). Add kerosene (polar liquid) to cement in flask till it is about half full. Mix thoroughly with glass rod to remove entrapped air. Continue stirring and add more kerosene till it is flush with the graduated mark. Dry the outside and weigh (W3). Entrapped air may be removed by vacuum pump, if available. Empty the flask, clean it refills with clean kerosene flush with the graduated mark wipe dry the outside and weigh (W4).

Calculations:

( W2 – W1)

Specific gravity =

(W2 – W1) – (W3 – W4) X 0.79

Where W1 = weight of empty flask.

W2 = weight of flask + cement.

W3 = weight of flask + cement + kerosene.

W4 = weight of flask + kerosene.

0.79= specific gravity of kerosene.

Limit: Specific gravity of cement = 3.15 g/cc .

SPECIFIC GRAVITY AND WATER ABSORPTION TEST.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:45:00 +0000

SPECIFIC GRAVITY AND WATER ABSORPTION TEST.

( IS : 2386 – PART – 3 )

INTRODUCTION:

The specific gravity of an aggregate is considered to be a measure of strength or quality of the material. The specific gravity test helps in the identification of stone.

Water absorption gives an idea of strength of aggregate. Aggregates having more water absorption are more porous in nature and are generally considered unsuitable unless they are found to be acceptable based on strength, impact and hardness tests.

Object:

To determine the specific gravity and water absorption of aggregates by perforated basket.

Apparatus:

a) A wire basket of not more than 6.3mm mesh or a perforated container of convenient size with thin wire hangers for suspending it from the balance.

b) A thermostatically controlled oven to maintain temperature of 100⁰ to 110⁰C.

c) A container for filling water and suspending the basket.

d) An airtight container of capacity similar to that of the basket.

e) A balance of capacity about 5 kg, to weigh accurate to 0.5 g, and of such a type and shape as to permit weighing of the sample container when suspended in water.

f) A shallow tray and two dry absorbent clothes, each not less than 750 X 450 mm.

Procedure:

About 2 kg of the aggregate sample is washed thoroughly to remove fines, drained and then placed in the wire basket and immersed in distilled water at a temperature between 22⁰ to 32⁰C with a cover of at least 50mm of water above the top of the basket. Immediately after immersion the entrapped air is removed from the sample by lifting the basket containing it 25mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per second. The basket and the aggregate should remain completely immersed in water for a period of 24 +/- 0.5 hours afterwards. The basket and the sample are then weighed while suspended in water at a temperature of 22⁰ to 32⁰C. In case it is necessary to transfer the basket and the sample to a different tank for weighing, they should be jolted 25 times as described above in the new tank to remove air before weighing. This weight is noted while suspended in water W1 g. The basket and the aggregate are then removed from water and allowed to drain for a few minutes, after which the aggregates are transferred to one of the dry absorbent clothes. The empty basket is then returned to the tank of water, jolted 25 times and weight in water W2 g. The aggregates placed on the absorbent clothes are surface dried till no further moisture could be removed by this cloth. Then the aggregates are transferred to the second dry cloth spread in a single layer, covered and allowed to dry for at least 10 minutes until the aggregates are completely surface dry. 10 to 60 minutes drying may be needed. The aggregates should not be exposed to the atmosphere, direct sunlight or any other source of heat while surface drying. A gentle current of unheated air may be used during the first ten minutes to accelerate the drying of aggregate surface. The surface dried aggregate is then weighed W3 g. The aggregate is placed in a shallow tray and kept in an oven maintained at a temperature of 110⁰C for 24 hours. It is then removed from the oven, cooled in an airtight container and weighed W4 g. At least two tests should be carried out, but not concurrently.

Calculations:

Weight of saturated aggregate suspended in water with the basket = W1 g

Weight of basket suspended in water = W2 g

Weight of saturated aggregate in water = (W1-W2) = Ws g.

Weight of saturated surface dry aggregate in air = W4 g

Weight of water equal to the volume of the aggregate = W3-(W1-W2) g.

Dry weight of aggregate W4

(i) Specific gravity = =

Weight of equal volume of water W3 – (W1-W2)

Dry weight of aggregate W4

(ii)Apparent Sp.gr. = =

(Weight of equal volume of water excluding air voids in aggregates) W4 – (W1-W2)

(iii) Water absorption = % by wt of water absorbed in terms oven dried wt of Agg. = (W3 – W4)/W4 x100

Limits: The Sp.gravity of aggregates ranges from 2.5 to 3.0 & WA of Agg ranges from 0.1 to 2%.

DETERMINATION OF SOUNDNESS OF CEMENT BY THE LE CHATELIER METHOD.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:44:00 +0000

DETERMINATION OF SOUNDNESS OF CEMENT

BY THE LE CHATELIER METHOD.

(IS: 4031 – part – 3)

Object:

Determination of the Soundness of cement by the Le Ch atelier method.

Apparatus:

The apparatus for conducting the test consists of small split cylinder of spring brass or other suitable metal of 0.5 mm thickness, forming a mould 30 mm internal diameter and 30 mm high. On either side of the split mould are attached two indicators with pointed ends, the distance from these ends to the center of the cylinder being 165 mm. The mould shall be kept in good condition with the Jaws not more than 0.50 mm apart.

Procedure:

Place the mould on a glass sheet and fill it with cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency. The paste shall be gauged in the manner and under the conditions prescribed in determination of consistency of standard cement paste, taking care to keep the edges of the mould gently together while this operation is being performed. Cover the mould with another piece of glass sheet, place a small weight on this covering glass sheet and immediately submerge the whole assembly in water at a temperature of 27⁰C +/- 2⁰C and keep there for 24 hours. Measure the distance separating the indicator points. Submerge the moulds again in water at the temperature prescribed above. Bring the water to boiling, with the mould kept submerge, in 25 to 30 minutes, and keep it boiling for three hours. Remove the mould from the water, allow it to cool and measure the distance between the indicator points. The difference between these two measurements represents the expansion of the cement.

Limits:

Expansion should not be more than 10 mm.

DETERMINATION OF FINENESS OF CEMENT.

(IS: 4031 – part – 3)

Object:

To determine the fineness of cement by dry sieving.

Apparatus:

a) Standard balance with 100 gm. weighing capacity.

b) IS : 90 micron sieve confirming to IS : 460 – 1962 and a Brush.

Procedure:

a) Break down any air-set lumps in the cement sample with fingers.

b) Weigh accurately 100 gms of the cement and place it on a standard 90 micron IS.sieve.

c) Continuously sieve the sample for 15 minutes.

d) Weigh the residue left after 15 minutes of sieving. This completes the test.

Result:

The percentage weight of residue over the total sample is reported.

Wt.of Sample Retained on the Sieve

% Weight of Residue =

Total Weight of the Sample

Limits:

The percentage residue should not exceed 10%.

Precautions:

Sieving shall be done holding the sieve in both hands and gentle wrist motion, this will involve no danger of spilling the cement, which shall be kept well spread out on the screen. More or less continuous rotation of the sieve shall be carried out throughout sieving.

Washers, shots and slugs shall not be used on the sieve. The underside of the sieve shall be lightly brushed with a 25 or 40 mm bristle brush after every five minutes of sieving.

Mechanical sieving devices may be used, but the cement shall not be rejected if it meets the fineness requirement when tested by the hand method.

SOFTENING POIN TEST ( RING AND BALL TEST )

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:43:00 +0000

SOFTENING POIN TEST ( RING AND BALL TEST ).

( IS : 1205 – 1978 )

INTRODUCTION:

Bitumen does not suddenly change from solid to liquid state, but as the temperature increases, it gradually becomes softer until it flows readily. All semi-solid state bitumen grades need sufficient fluidity before they are used for application with the aggregate mix. For this purpose bitumen is sometimes cutback with a solvent like kerosene. The common procedure however is to liquefy the bitumen by heating. The softening point is the temperature at which the substance attains particular degree of softening under specified condition of test. For bitumen, it is usually determined by ‘Ring and Ball’ test.

Object:

To determine the softening point of the bitumen by ‘Ring and Ball’ apparatus.

Apparatus:

a) Ring and Ball apparatus – It consists

(i) Steel Balls – 2 nos.each has a diameter of 9.5mm and weight is 2.5+/-0.05gm.

(ii) Brass Rings – 2 nos. each 6.4mm depth, inside diameter at top 17.5mm, inside diameter at bottom 15.9mm and outside diameter 20.6mm and three equally spaced ball guides.

(iii) Support - The metallic support is used for placing pair of rings. The upper surface of the rings is adjusted to be 50mm below the surface of water or liquid contained in the bath. A distance of 25mm between the bottom of the rings and top surface of the bottom plate of support is provided. It has a housing for a suitable thermometer.

b) Thermometer – 0⁰C to 350⁰C – sensitivity 0.1⁰C.

c) Bath and stirrer – A heat resistant glass container of 85mm diameter and 120mm depth is used.

Procedure:

Sample material is heated to a temperature between 75 and 100⁰C above the approximate softening point until it is completely fluid and is poured in heated rings placed on metal plate. To avoid sticking of the bitumen to metal plate, coating is done to this with a solution of glycerin and dextrin. After cooling the rings in air for 30 minutes, the excess bitumen is trimmed and rings are placed in the support as mentioned in item(iii) above. At this time the temperature of distilled water is kept at 5⁰C. This temperature is maintained for 15 minutes after which the balls are placed in position. The temperature of water is raised at uniform rate of 5⁰C per minute with a controlled heating unit, until the bitumen softens and touches the bottom plate by sinking of balls. At least two observations are made.

Results:

The temperature at the instant when each of the ball and sample touches the bottom plate of support is recorded as softening value.

Limits:

Bitumen Grade A 35 & S 35 A 45 & S 45 A 55 & S 55 A 65 & S 65 A 90 & S 90 A 200 & S 200

Softening point 50 to 650 C 45 to 600 C 45 to 600 C 40 to 550 C 35 to 500 C 30 to 350C

DETERMINATION OF WORKABILITY OF CONCRETE (SLUMP

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:35:00 +0000

DETERMINATION OF WORKABILITY OF CONCRETE (SLUMP TEST)

(IS: 1199 – 1959)

Object:

This method of test specifies the procedure to be adopted, either in the laboratory or during the progress of work in the field, for determining, by the slump test, the consistency of concrete.

Apparatus:

a) Mould: the mould for the test specimen shall be in the form of the frustum of a cone having the following internal dimensions:

Dimensions cm

Bottom diameter. 20

Top diameter. 10

Height. 30

b) Tamping Rod: The tamping rod shall be of steel or other suitable material, 16 mm in diameter, 0.6m long and rounded at one end.

Procedure:

The internal surface of the mould shall be thoroughly cleaned and freed from superfluous moisture and any set concrete before commencing the test. The mould shall be placed on a smooth, horizontal, rigid and non-absorbent surface, such as a carefully leveled metal plate, the mould being firmly held in place while it is being filled. The mould shall be filled in four layers, each approximately one-quarter of the height of the mould. Each layer shall be tamped with 25 strokes of the rounded end of the tamping rod. The strokes shall be distributed in a uniform manner over the cross-section of the mould and for the second and subsequent layers shall penetrate into the underlying layer. The bottom layer shall be tamped throughout its depth. After the top layer has been rodded, the concrete shall be struck off level with a trowel or the tamping the rod, so that the mould is exactly filled. Any mortar, which may have leaked out between the mould and the base plate, shall be cleaned away. The mould shall be removed from the concrete immediately by raising it slowly and carefully in a vertical direction. This allows the concrete to subside and the slump shall be measured immediately by determining the difference between the height of the mould and that of the highest point of the specimen being tested. The above operation shall be carried out at a place free from vibration or shock, and within a period of two minutes after sampling.

The slump measured shall be recorded in terms of millimeters of subsidence of the specimen during the test. Any slump specimen which collapses or shears off laterally gives incorrect result and if this occurs the test shall be repeated with another sample.

FLAKINESS & ELONGATION INDEX TEST( SHAPE TEST ).

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:34:00 +0000

FLAKINESS & ELONGATION INDEX TEST( SHAPE TEST ).

( IS : 2386 – PART – 1 )

INTRODUCTION:

The particle shape of aggregates is determined by the percentages of flaky and elongated particles contained in it. For base course and construction of bituminous and cement concrete types, the presence of flaky and elongated particles are considered undesirable as they may cause inherent weakness with possibilities of breaking down under heavy loads. The angularity number i.e., flaky and elongation has considerable importance in the gradation requirements of various types of mixes such as bituminous concrete, cement concrete and soil aggregate mixes.

Object:

To determine the flakiness and elongation of the aggregates by standard flakiness gauge and elongation gauges.

Apparatus:

a) Flakiness gauge (Thickness gauge)

b) Elongation gauge (Length gauge)

Procedure:

a) Flakiness Index: The sample is sieved with the sieves mentioned in above. A minimum of 200 pieces of each fraction to be tested is taken and weighed. In order to separate flaky materials, each fraction is then gauged for thickness on a thickness gauge. The amount of flaky material passing the gauge is weighed to an accuracy of at least 0.1 percent of the test sample.

Calculation:

In order to calculate the flakiness index of the entire sample of aggregates first the weight of each fraction of aggregate passing and retained on the specified set of sieves is noted (X1, X2, X3… etc). Each of the particle from this fraction of aggregate is tried to be passed through the slot of the specified thickness of the thickness gauge are found and weighed (x1, x2, x3…etc). Then the flakiness index is the total weight of the flaky material passing the various thickness gauges expressed as a percentage of the total weight of the sample gauged.

(x1 + x2 + x3 + …)

Flakiness Index = X 100

(X1 + X2 + X3 + …)

b) Elongation Index: The sample is sieved through the IS sieves specified as above. A minimum of 200 pieces of each fraction is taken and weighed. In order to separate elongated material, each fraction is then gauged individually for length in a length gauge. The pieces of aggregates from each fraction tested which could not pass through the specified gauge length with its long side are elongated particles and are collected separately to find the total weight of aggregates retained on the length gauge from each fraction. The total amount of elongated material retained by the length gauge is weighed to an accuracy of at least 0.1 percent of the weight of the sample.

Calculation:

In order to calculate the Elongation index of the entire sample of aggregates first the weight of each fraction of aggregate passing and retained on the specified set of sieves is noted (Y1, Y2, Y3… etc). Each piece of these are tried to be passed through the specified length of the gauge length with its longest side and those elongated pieces which do not pass the gauge are separated and weighed (y1, y2, y3…). Then the Elongation index is the total weight of the material retained on the various length gauges, expressed as a percentage of the total weight of the sample gauged.

(y1 + y2 + y3 +…)

Elongation Index = X 100

(Y1 + Y2 + Y3 + …)

Combined Flakiness & Elongation Index: To determine this combined proportion, the flaky stone from a representative sample should first be separated out. Flakiness index is weight of flaky stone metal divided by weight of stone sample. Only the elongated particle is separated out from the remaining (non flaky) stone metal. Elongation index is weight of elongated particles divided by total non-flaky particles. The value of flakiness index and elongation index so found are added up.

Limits: (i) Flakiness Index for Bituminous and Non-bituminous Mixes = Max. 15%, (ii) Elongation Index for Bituminous and Non-bituminous mixes = Max. 15%, (iii) Combined Flakiness and Elongation Index for Bituminous and Non-bituminous mixes = Max.30% & (iv) Flakiness Index for Concrete mixes = Max.35%

SAND EQUIVALENT TEST.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:33:00 +0000

SAND EQUIVALENT TEST.

( IS : 2720 – PART – 37 )

INTRODUCTION:

This test is intended to serve as a rapid field test to show the relative proportions of fine dust or clay like material in soils or graded aggregates.

Apparatus:

1) A graduated plastic cylinder, rubber stopper, irrigator tube, weighted foot assembly, and siphon assembly, all confirming to their respective specifications and dimensions. Fit the siphon assembly to a 4 liters bottle of working calcium chloride solution placed on a shelf 915 +/- 25mm above the work surface. In lieu of the specified 4liter bottle, a glass or plastic vat having a larger capacity may be used providing the liquid level of the working solution is maintained between 915 to 1175mm above the work surface.

2) A 85 ml tinned box approximately 57mm in diameter, with gill style cover and having a capacity of 85 +/- 5ml.

3) A wide mouth funnel approximately 100mm in diameter at the mouth.

4) A clock or watch reading in minutes and seconds.

5) A mechanical shaker having a throw of 203.2 +/- 1.02mm and operating at 175 +/- 2 cycles per minute.

6) Dissolve the calcium chloride in 1.89 liters of distilled water. Cool the solution, then filter and add the glycerin and formaldehyde to the filtered solution, mix well, and dilute to 3.79 liters with distilled or dematerialized water.

7) Prepare the working calcium chloride by diluting one measuring tin full 85 +/- 5ml of the stock calcium chloride solution 3.79 liters with water. Use distilled water for the normal preparation of the working solution.

Sample preparation:

The sand equivalent test shall be performed on soils or graded aggregate materials passing the 4.75mm sieve. All aggregates of fine-grained soil material shall be pulverized to pass the 4.75mm sieve, and all fines shall be cleaned from the particles retained on the 4.75mm sieve and included with the material passing the 4.75mm sieve. Split enough of the original sample to yield slightly more than 85ml tin measures of material passing the 4.75mm sieve. Use extreme care to obtain a truly representative portion of the original sample.

Procedure:

Siphon 101.6 +/- 2.5ml of working calcium chloride solution into the paste cylinder. Pour the prepared test sample from the measuring tin into the plastic cylinder using the funnel to avoid spillage. Tap the bottom of the cylinder sharply on the heel of the hand several times to release air bubbles and to promote thorough wetting of the sample. Allow the wetted sample to stand undisturbed for 10 minutes. At the end of the 10-minute soaking period, stopper the cylinder, then loosen the material from the bottom by partially inverting the cylinder and shaking it simultaneously. Hold the cylinder in a horizontal position and shake it vigorously in a horizontal linear motion from end to end. Shake the cylinder 90 cycles in approximately 30 seconds using a throw of 229 +/- 25mm. A cycle is defined as a complete back and front motion. To properly shake the cylinder at this speed, it will be necessary for the operator to shake with the forearms only, relaxing the body and shoulders.

Allow the cylinder and contents to stand undisturbed to 20 minutes, read the level of the top of the clay suspension. This is referred to as the ‘clay reading’. After the clay reading has been taken, the ‘sand reading’ shall be obtained by the following method:

When using the weighted foot assembly having the sand indicator on the rod of the assembly, place the assembly over the cylinder and gently lower the assembly towards the sand. Do not allow the indicator to hit the mouth of the cylinder as the assembly is being lowered. As the weighted foot comes to rest on the sand, tip the assembly toward the graduations on the cylinder until the indicator touches the inside of the cylinder. Subtract 254mm from the level indicated by the extreme top edge of the indicator and record this value as the ‘sand reading’.

Calculations:

Sand equivalent (SE) to the nearest 0.1 using the following formula:

Sand Reading

SE = -------------------------- X 100

Clay Reading

PENETRATION TEST

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:33:00 +0000

PENETRATION TEST

( IS : 1203 – 1978 )

INTRODUCTION:

Penetration test is the test on bitumen to grade the material in term of its hardness.

Object:

To determine the penetration of bitumen by penetration test.

Apparatus:

a) Container: A flat-bottomed cylindrical metallic container 55mm in diameter and 35mm or 57mm in height.

b) Needle: A straight, highly polished hard steel needle.

c) Water bath: A water bath is maintained at 25 +/- 1⁰C containing not less than 10 liters of water, the sample is immersed to depth not less than 100mm from the top and supported on a perforated shelf not less than 50mm from the bottom of the bath.

d) Penetrometer: Electrically operated automatic penetrometer / Manually operated penetrometer. It is an apparatus, which allows the needle assembly of gross weight 100gm to penetrate without appreciable friction for the desired duration of time 5 sec. The dial is accurately calibrated to give penetration value in units of one tenth of an mm.

e) Transfer tray: A small tray, which can keep the container fully immersed in water during the test.

f) Stop Watch.

Procedure:

The bitumen is softened to a pouring consistency between 75⁰C and 100⁰C above the approximate temperature at which bitumen softens. The sample material is thoroughly stirred to make it homogenous and free from air bubbles and water. The sample material is then poured into the containers to a depth at least 15 mm more than the expected penetration. The sample containers are cooled in atmosphere temperature not lower than 13⁰C for one hour. Then they are placed in temperature controlled water bath at a temperature of 25⁰C for a period of one hour.

The sample container is placed in the transfer tray with water from the water bath and placed under the needle of the penetrometer. The weight of needle, shaft and additional weight are checked. The total weight of this assembly should be 100gm.

Using the adjusting screw, the needle assembly is lowered and the tip of the needle is made to just touch the top surface of the sample, the needle assembly is clamped in this position. The contact of the tip of the needle is checked using the mirror placed on the rear of the needle. The initial reading of the penetrometer dial is either adjusted to zero or the initial reading is taken before releasing the needle. The needle is released exactly for a period of 5 secs. by pressing the knob and the final reading is taken on the dial. At least three measurements are made on this sample by testing at distance of not less than 10mm apart. After each test the needle is disengaged and cleaned with benzene and carefully dried. The sample container is also transferred in the water bath before next testing is done so as to maintain a constant temperature of 25⁰C. The test is repeated with sample in the other containers.

Results:

The difference between the initial and final penetration readings is taken as the penetration value.

Bitumen Grade A35 &S35 A45 & S45 A55 & S55 A65 &S65 A90 &S90 A200 & S200

Penetration Value 30 to 40 40 to 50 50 to 60 60 to 70 80 to 100 175 to 225

DETERMINATION OF NORMAL CONSISTENCY

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:27:00 +0000

DETERMINATION OF NORMAL CONSISTENCY

(IS: 4031 – part – 4)

Object:

Determination of the quantity of water required to produce a cement paste of standard consistency.

Apparatus:

Vicat apparatus (confirming to IS : 5513 – 1968) with plunger ( 10mm in dia ).

Theory:

The standard consistency of a cement paste is defined as that consistency which will permit the vicat plunger to penerate to a point 5 to 7 mm from the bottom of the vicat mould, when the cement paste is tested as described in the following procedure.

Procedure:

Prepare a paste of weighted quantity of cement ( 350 gms) with a weighted quantity of water, start with 30% water of 350 gms of cement taking care that the time of gauging is not less than 3 minutes and not more than 5 minutes and the gauging shall be completed before any sign of setting occurs. The gauging time shall be counted from the time of adding the water to the dry cement until commencing to fill the mould. Fill the vicat mould with this paste, the mould resting upon a non-porous plate. After completely filling the mould, trim off the surface of the paste, making it in level with the top of the mould. The mould may slightly be shaken to expel the air. Place the test block with the mould, together with the non-porous resting plate, under the rod bearing the plunger ( 10mm dia ) lower the plunger gently to touch the surface of the test block and quickly release, allowing it to penetrate into the paste. This operation shall carried out immediately after filling the mould. Prepare trial pastes with varying percentages of water and test as described above until the amount of water necessary for making the standard consistency as defined above is obtained. Express the amount of water as a percentage by weight of the dry cement.

Precautions:

Use clean appliances for gauging. The temperature of cement and water and that of test room, at the time when the above operations are being performed, shall be 27⁰C +/- 2⁰C. the room temperature shall be maintained at 27⁰C +/- 2⁰C.

DETERMINATION OF INITIAL AND FINAL SETTING TIMES OF CEMENT.

( IS : 4031 – part – 5 )

Sample: 350 gms of cement is taken.

Procedure:

Preparation of Test Block

Prepare a neat cement paste by gauging 350 gms of cement with 0.85 times the water required to give a paste of standard consistency. The paste shall be gauged in the manner and under the conditions prescribed in determination of consistency of standard cement paste. Start a stopwatch at the instant when water is added to the cement. Fill the mould with the cement paste gauged as above, the mould resting on a non-porous plate, fill the mould completely and smooth off the surface of the paste making it level with the top of the mould. The cement block thus prepared in the mould is the test block. Use clean appliances for gauging. The temperature of water and that of the test room, and the time gauging, shall be 27⁰C +/- 2⁰C. During the test, the block shall be kept at a temperature of 27⁰C +/- 2⁰C and at not less than 90% relative humidity.

Determination of Initial Setting Time:

Place the test block confined in the mould and resting on the non-porous plate, under the rod bearing initial setting needle, lower the needle gently in contact with the surface of the test block and quickly release, allowing it to penetrate into the test block. In the beginning the needle will completely pierce the test block. Repeat this procedure until the needle, when brought in contact with the test block and released as described above, fails to pierce the block for 5 +/- 0.5 mm measured from the bottom of the mould. The period lapsing between the time water is added to the cement and the time at which the needle fails to pierce the test block by 5 +/- 0.5 mm shall be the initial setting time.

Determination of Final Setting Time:

Replace the needle of the vicat apparatus by the needle with an annular ring. The cement shall be considered as finally set when, upon applying the needle gently to the surface of the test block, the needle makes an impression thereon, while the outer ring fails to do so. The period elapsing between the time when water is added to the cement and the time at which the needle makes an impression on the surface of the test block while the attachment fails to do so, shall be the final setting time.

Limits: Initial Setting Time, minimum = 30 minutes & Final Setting Time, maximum = 600 minutes.

MOISTURE CONTENT TEST.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:26:00 +0000

MOISTURE CONTENT TEST.

( IS : 2720 – PART – 2 )

Object:

To determine the water content of a soil sample by oven drying method / sand bath method / Rapid moisture meter method.

Apparatus:

1) Non-corrodible airtight containers.

2) Heat resistant tray – 5 to 7 cm deep.

3) Rapid moisture meter and absorbent (calcium carbide).

4) Oven, balance and heater / stove etc.

Procedure:

(A) Oven drying method: Take about 30 to 50 gms of soil sample if it is fine grained and about 250 to 300 gms if it is coarse grained soil in to the container and weigh it (W1). Place the container in the oven and dry for 24 hours at temperature of 105⁰ to 110⁰C. Remove the container from the oven replace the lid and cool it, after cooling weigh the container along with lid (W2). Clean and dry the container and weigh it (W3).

Calculations:

(W1 – W2)

Water content, w % = --------------- X 100

(W2 – W3)

(B) Sand bath method: Clean the container with lid or the tray, as the case may be dry and weigh (W1). Take the required quantity of the soil specimen in the container crumbled and placed loosely and weigh (W2). Add a few pieces of white paper if necessary. Place the container with the lid removed or the tray on the sand bath and heat the sand bath. Care shall be taken not to get the sand bath too hot. During heating, the specimen shall be turned frequently and thoroughly with the palette knife to assist the evaporation of water, care being taken to see that no soil is lost in the process. When drying is complete, remove the container from the sand bath, cool and weigh (W3).

Calculations:

(W2 – W3)

Water content, w % = --------------- X 100

(W3 – W1)

Note: Avoid over heating, A convenient method of detecting overheating of the soil is by the use of small pieces of white paper mixed the soil. Overheating is indicated if the paper turns brown.

(C) Rapid Moisture Meter: Set up the balance, place sample in pan till the mark on the balance arm mass lines up with the index mark (taken approximately 6 grams of soil). Unclamp the clamping screw of the instrument sufficiently to move the U-clamp off the cup. Lift off the cup, check that cup and body are clean; otherwise clean it by using a brush. Hold the body horizontal and gently deposit one level scoopful of absorbent (calcium carbide) halfway inside the chamber. Then lay the chamber down without disturbing the absorbent charge. Transfer the soil weighed out as above from the pan to the cup. Holding cup and chamber approximately horizontal bring them together without disturbing sample or absorbent, bring the U-clamp round and clamp the cup tightly into place.

With gauge downwards (except when the steel balls are used) shake the moisture meter up and down vigorously for 5 seconds, then quickly turn it so that the gauge is upwards, give a tap to the body of the moisture meter to ensure that all the contents fall into the cup. Hold the rapid moisture meter downwards, again shake for 5 seconds then turn it with gauge upwards and tap. Hold for one minute and repeat this, when the needle comes to rest on the reading. The reading on the meter is the percentage of water content of the wet mass.

Calculations: From the water content (m) obtained on the wet mass basis as the reading on the rapid moisture meter, the water content (w) on the dry mass basis shall be calculated as follows:

m where, m = moisture content obtained from rapid moisture meter.

w, % = ------------ X 100 w = moisture content on the dry mass basis

(100 – m)

LOSS ON HEATING OF BITUMINOUS MATERIALS.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:25:00 +0000

LOSS ON HEATING OF BITUMINOUS MATERIALS.

( IS : 1205 – 1978 )

INTRODUCTION:

The loss in weight (exclusive of water) of bituminous materials when heated is called loss on heating of bituminous materials.

Object:

To determine the loss on heating of bituminous materials.

Apparatus:

a) Oven – heating capacity is minimum 180⁰C and interior dimensions min.330X330mm.

b) Aluminum Rotating shelf - the self shall be suspended by vertical shaft and centered with respect to the horizontal interior dimensions minimum diameter of 250mm, and shall be provided with a mechanical means of rotating it at the rate of 5 to 6 rpm.

c) Thermometer – 0 to 360⁰C – sensitivity 0.1⁰C.

d) Containers- Metal or glass cylindrical containers shall have a flat bottom and diameter 55mm, 35mm depth minimum.

e) Balance – sensitivity 0.01gm.

Procedure:

Heat the sample with care, stirring constantly to prevent local overheating, until the sample has become sufficiently fluid to pour. Place the sample in container and cool the sample to room temperature and then weigh to the nearest 0.01gm. Bring the oven to a temperature of 163⁰C and place the container in oven for period of 5 hr. Remove the sample from the oven, cool to room temperature, and weigh to the nearest 0.01gm. And calculate the loss due to heating.

Limits: Loss on heating of all grades, except A200 & S200 of bitumen is maximum 1% by mass. Loss on heating of grade A200 & S200 is maximum 2% by mass.

Hydrometer method.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:24:00 +0000

Hydrometer method.

Apparatus:

a) Density hydrometer confirming to IS: 3104-1965 – (Range 0.995 – 1.030).

b) Two glass-measuring cylinders of 1000ml capacity with ground glass or rubber stoppers about 7cm diameter and 33cm high marked at 1000ml volume.

c) Thermometer to cover the range 0 to 50⁰C, accurate to 0.50⁰C.

d) Water bath or constant temperature room

e) Stirring apparatus

f) 75 micron sieve.

g) Balance accurate to 0.01g

h) Stop watch

i) Wash bottles containing distilled water

j) Glass rod, about 15 to 20 cm long and 4 to 5 mm in diameter

k) Reagents: Hydrogen peroxide, Hydrochloric acid N solution and Sodium hexametaphosphate.

l) Conical flask of 1000ml capacity

m) Funnel, filter paper, measuring cylinder of 100ml capacity and blue litmus papers.

Procedure:

(A) Calibration of Hydrometer:

1. Determination of volume of the hydrometer bulb (V_h): Pour about 800ml of distilled water in the 1000ml-measuring cylinder and note the reading at the water level. Immerse the hydrometer in water and note the water reading. The difference between the two readings is recorded as the volume of the hydrometer bulb plus the volume of that part of the stem, which is submerged. For practical purposes, the error due to the inclusion of this stem volume may be neglected. Alternatively, weigh the hydrometer to the nearest 0.2g. This weight in grams is recorded as the volume of the hydrometer in ml. This includes the volume of the bulb plus the volume of the stem. For practical purposes the error due to the inclusion of the stem may be neglected.

2. In order to find the area of cross-section (A) of the measuring cylinder in which the hydrometer is to be used, measure the distance, in cm, between two graduations of the cylinder. The cross-section area (A) is then equal to the volume included between the two graduations divided by the distance between them.

3. Measure the distance (h) from the neck to the bottom of the bulb, and record it as the height of the bulb.

4. With the help of an accurate scale, measure the height (H) between the necks of the hydrometer to each of the other major calibration marks (R_h).

5. Calculate the effective depth (H_e) corresponding to each of the major calibration marks (or hydrometer readings, R_h) by the following expression:

1 V_h

He = H + (h - )

2 A

6. Draw a calibration curve between H_e and R_h, which may be used for finding the effective depth (H_e) corresponding to hydrometer readings (R_h) obtained during the test.

7. Meniscus correction (C_m) : Insert the hydrometer in the measuring cylinder containing about 700ml of water. Take the readings of the hydrometer at the top and bottom of the meniscus. The difference between two readings is taken as the meniscus correction (C_m), which is a constant for hydrometer. During the actual sedimentation test, the readings should be taken at the bottom of the meniscus but since the soil suspension is opaque, readings are taken at the top of meniscus. The meniscus correction is always positive.

(B) Pre- treatment of soil:

1. Weigh accurately (to 0.01g) 50 to 100 g of oven dried soil sample (W_d) passing the 0.075mm IS sieve. If the percentage of soluble salts is more than one percent, the soil should be washed with water before further treatment, taking care to see that the soil particles are not lost.

2. Add 150ml of hydrogen peroxide to the soil sample placed in a wide mouth conical flask and stir it gently for few minutes with a glass rod. Cover the flask with glass and leave it to stand overnight.

3. Next morning, the mixture in the conical flask is gently heated in an evaporating dish, stirring the contents periodically. Reduce the volume to about 50ml by boiling. With very organic soils additional peroxide may be required to complete the oxidation.

4. If the soil contains insoluble calcium compounds, add about 50ml of hydrochloric acid to the cooled mixture of soil obtained in step 3. The solution is stirred with a glass rod for a few minutes and allowed to stand for one hour or for longer periods, if necessary. The solution will have an acid reaction to litmus.

5. Filter the mixture and wash it with warm water until the filtrate shows no acid reaction to litmus. Transfer the damp soil on the filter paper and funnel to the evaporating dish using a jet of distilled water. Place the dish and its contents to the oven. Take the weight (W_b) of the oven-dried soil remaining after pre-treatment and find the loss of weight due to pre-treatment.

(C) Dispersion of soil:

1. To the oven-dried soil, add 100ml of sodium hexametaphosphate solution and warm the mixture gently for about 10 minutes. Transfer the mixture to the cup of the mechanical mixer using a jet of distilled water, and stir it well for about 15 minutes. The sodium hexametaphosphate solution is prepared by dissolving 33 g of sodium hexametaphosphate and 7 grams of sodium carbonate in distilled water to make one liter of solution. This solution is unsuitable and should be freshly prepared approximately once in a month.

2. Transfer the soil suspension to the 75 micron IS sieve placed on a receiver and washes the soil on this sieve using jet of distilled water from a wash bottle. The amount of distilled water used during this operation may be about 500ml.

3. Transfer the soil suspension passing the 75-micron IS sieve to the 1000ml-measuring cylinder, and adds more water to make the volume to exactly 1000ml in the cylinder.

4. Collect he material retained on 75-micron sieve and put it in the oven for drying. Determination the dry weight of soil retained on 75-micron sieve.

(D) Sedimentation test with hydrometer:

1. Insert a rubber bung or any other suitable cover on the top of the 1000ml-measuring cylinder containing the soil suspension and shake it vigorously end over end. Stop shaking and allow it to stand. Immediately, start the stopwatch, and remove the top cover from the cylinder.

2. Immerse the hydrometer gently to a depth slightly below its floating position and then allow it to float freely. Take the hydrometer readings after periods of 0.5, 1, 2 and 4 minutes. Take out the hydrometer, rinse it with distilled water and allow it to stand in a jar containing distilled water at the same temperature as that of the test cylinder.

3. The hydrometer is re-inserted in the suspension and readings are taken after periods of 8, 15 and 30 minutes; 1, 2 and 4 hours after shaking. The hydrometer should be removed, rinsed and placed in the distilled water after each reading. After the end of 4 hours, readings should be taken once or twice within 24 hours.

4. Composite correction (C): In order to determine the composite correction, put 100ml of dispersing agent solution in another 1000ml measuring cylinder and make it to 1000ml by adding distilled water. The cylinder should be maintained at the same temperature as that of the test cylinder containing soil specimen. Insert the hydrometer in this comparison cylinder containing distilled water and the dispersing agent and take the reading corresponding to the top of the meniscus. The negative of the hydrometer reading so obtained gives the composite correction (C). The composite correction is found before the start of the test, and also at every time intervals of 30 minutes, 1 hour, 2 hours and 4 hours after the beginning of the test, and afterwards, just after each hydrometer reading is taken in test cylinder.

5. The temperature of the suspension should be observed and recorded once during the first 15 minutes and then after every subsequent reading.

Calculations:

(1) The loss in weight in pre-treatment of the soil in percentage is calculated from the following expression:

W_bWhere, P = loss in weight in percentage

P = 1 - ------- X 100 W_d = weight of dry soil sample taken from the soil passing 2mm Sieve

W_dW_b = weight of the soil after pre-treatment

(2) The diameter of the particle in suspension at any sampling time t is calculated from:

D = 10^-5M ( H_e / t ) ^0.5Where, M = poise constant factor

H_e = effective depth of the hydrometer

t = elapsed time, minutes

(3) The percentage finer N^/ based on the weight W_d is calculated from:

100 G Where, N^/ = percentage finer, based on the weight of dry soil sample W_d

N^/ = X R W_d = weight of dry soil sample taken from the soil sample passing 2mm sieve.

W_d ( G – 1 ) G = specific gravity of the soil passing 75 micron sieve.

R = corrected hydrometer reading

R = R_h^/ + C

R_h = R_h^/ + C_m

Where, R_h^/= observed hydrometer reading

R_h = hydrometer reading, corrected for meniscus correction

(4) The percentage finer (N) based on the total weight of dry soil sample (W) is obtained from the relation:

N = N^/ X (W^/ / W) Where, W^/ = cumulative weight passing 2mm sieve.

Values of Factor ‘M’

GRAIN SIZE ANALYSIS.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:23:00 +0000

GRAIN SIZE ANALYSIS.

( IS : 2720 – PART – 4 )

INTRODUCTION:

Most of the methods for soil identification and classification are based on certain physical properties of the soils. The commonly used properties for the classification are the grain size distribution, liquid limit and plasticity index. These properties have also been used in empirical design methods for flexible pavements, and in deciding the suitability of sub grade soils.

The soils received from the field are divided into two parts: one, the fraction retained on 2mm sieve and the other passing 2mm sieve. The sieve analysis also may be carried out separately for these two fractions. The fraction retained on 2mm sieve may be subjected to dry sieving using bigger sieves and that passing 2mm sieve may be subjected to wet sieving; however if this fraction consists of single grained soil with negligible fines passing 0.075mm size, dry sieving may be carried out.

Apparatus:

Various apparatus include set of standard sieves of different sieve sizes, balance, rubber covered pestle and mortar, oven, riffle and sieves shaker.

Procedure:

(a) For the fraction retained on 2.0mm sieve: Sufficient quantity of the dry soil retained on 2.0mm sieve is weighed out. The quantity of sample taken may be increased when the maximum size of particles is higher. The sample is separated into various fractions by sieving through the set of sieves of sizes 100, 63, 20, 6, 4.75 and 2 mm IS sieves. Additional sieve size may also be introduced if necessary. After initial sieving, the material retained on each sieve is collected, the lumps broken down using mortar and rubber covered pestle and is re-sieved thus the soil fraction retained on each sieve is carefully collected and weighed.

(b) For the fraction passing 2.0mm sieve and retained on 0.075mm sieve: Dry sieving may be done in the case of soils which are cohesion less, single grained and without lumps. Rifling or quartering method takes the required quantity of soil sample, dried in oven at 105⁰ to 110⁰C and is subjected to dry sieve analysis using a set of sieves with sieve openings 2.0, 0.6, 0.425, 0.15 and 0.075 mm, pan and lid, additional sieves may be used or any of the sieves removed, depending upon the requirement of the test. The material retained on each sieve and on the pan are separately collected and weighed.

Wet sieving may be adopted in the case of clayey or cohesive soils. Required quantity of sample taken by riffling is weighed. The sample is spread in a tray or bucket and covered with water. In case of soils having fractions that are likely to flocculate a dispersing agent like sodium hexametaphosphate (2.0g) or sodium hydroxide (1.0g) and sodium carbonate (1.0g) per liter of water may be added to the water. The mix is stirred and left for soaking. The soaked soil specimen is placed over the set of sieves of sizes with the finest sieve and pan at the bottom and washed thoroughly. Washing is continued till the water passing each sieve is substantially clean. The fraction of each sieve is emptied carefully without loss of material in separate trays, oven dried at 105⁰ to 110⁰C and each fraction weighed separately.

Calculations:

The weight of dry soil fractions retained on each sieve is calculated as a percentage of the total dry weight of the sample taken.

Results:

The results are plotted on a semi-logarithmic graph with the grain size or sieve size on the X-axis in log. scale and the percentage finer of each sieve on the Y-axis in ordinary scale. The smooth curve joining the points thus obtained is known as the particle size distribution curve or diagram.

Uniformity coefficient of soil, C_u = D₆₀ / D₁₀

Coefficient of curvature, C_c = (D₃₀)² / (D₁₀ X D₆₀)

Where, D60, D30 and D10 are particle sizes corresponding to 60, 30 and 10 percent finer.

FREE SWELL INDEX TEST.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:23:00 +0000

FREE SWELL INDEX TEST.

( IS : 2720 – PART – 40 )

Object:

To determine the free swell index of soils.

Apparatus:

1) 425 micron IS sieve

2) Glass graduated cylinders – 2 nos 100ml capacity

3) Distilled water and kerosene.

Procedure:

Take two 10 grams soil specimens of oven dry soil passing through 425-micron IS sieve. Each soil specimen shall be poured in each of the two glass graduated cylinders of 100ml capacity. One cylinder shall then be filled with kerosene oil and the other with distilled water up to the 100ml mark. After removal of entrapped air the soils in both the cylinders shall be allowed to settle. Sufficient time (not less than 24 hours) shall be allowed for the soil sample to attain equilibrium state of volume without any further change in the volume of the soils. The final volume of soils in each of the cylinders shall be read out.

Calculations:

The level of the soil in the kerosene-graduated cylinder shall be read as the original volume. The soil samples, kerosene being a non-polar liquid does not cause swelling of the soil. The level of the soil in the distilled water cylinder shall be read as the free swell level. The free swell index of the soil shall be calculated as follows:

(Vd – Vk)

Free swell index, percent = ----------- X 100

Where, Vd = the volume of soil specimen read from the graduated cylinder

containing distilled water.

Vk = the volume of soil specimen read from the graduated cylinder

containing kerosene.

FLASH AND FIRE POINT TEST. ( IS : 1209 – 1978 )

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:22:00 +0000

FLASH AND FIRE POINT TEST.

( IS : 1209 – 1978 )

INTRODUCTION:

Bituminous materials leave out volatiles at high temperatures depending upon their grade. These volatile catch fire causing a flash. This condition is very hazardous and it is therefore essential to qualify this temperature for each bitumen grade.

Flash point: The flash point of a material is the lowest temperature at which the vapour of substance momentarily takes fire in the form of a flash under specified condition of test.

Fire point: The fire point is the lowest temperature at which the material gets ignited and burns under specified condition of test.

Object:

To determine the flash and fire point of bitumen by Pensky-Martens closed tester.

Apparatus:

a) Pensky-Martens closed tester consist of cup, lid, stirrer device, shutter, flame exposure device.

b) Thermometer ( 0 – 350⁰C) – sensitivity – 0.1⁰C.

Procedure:

The material is filled in the cup up to a filling mark. The lid is placed to close the cup in a closed system. All accessories including thermometer of the specified range are suitably fixed. The bitumen sample is then heated. The test flame is lit and adjusted in such a way that the size of a bleed is of 4mm diameter. The heating is done at the rate of 5⁰C to 6⁰C per minute. The stirring is done at a rate of approximately 60 revolutions per minute. The test flame is applied at intervals depending upon the expected flash and fire points. First application is made at least 17⁰C below the actual flash point and then at every 1⁰C to 3⁰C. The stirring is discontinued during the application of the test flame.

Results:

The flash point is taken as the temperature read on the thermometer at the time of the flame application that causes a bright flash in the interior of the cup in closed system. For open cup it is the instance when flash appears first at any point on the surface of the material. The heating is continued until the volatiles ignite and the material continues to burn for 5 seconds. The temperature of the sample material when this occurs is recorded as the fire point.

Limits: The flash point for all grades of bitumen materials is 175⁰C, minimum.

DUCTILITY TEST. ( IS : 1208 – 1978 )

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:21:00 +0000

DUCTILITY TEST.

( IS : 1208 – 1978 )

INTRODUCTION:

In the flexible pavement construction where bitumen binders are used, it is of significant importance that the binders form ductile thin films around the aggregates. This serves as a satisfactory binder in improving the physical interlocking of the aggregates.

Object:

To determine the ductility of the bituminous material.

Apparatus:

a) Ductility machine.

b) Briquette moulds.

c) Knife.

Procedure:

The bitumen sample is melted to a temperature of 75 to 100⁰C above the approximate softening point until it is fluid. It is strained through 90 micron sieve, poured in the mould assembly and placed on a brass plate, after a solution of glycerin and dextrin is applied at all surfaces of the mould exposed to bitumen. After 30 to 40 minutes, the plate assembly along with the sample is placed in water bath maintained at 27⁰C for 30 minutes. The sample and mould assembly are removed from water bath and leveling the surface using hot knife cuts off excess bitumen material. After trimming the specimen, the mould assembly-containing sample is replaced in water bath maintained at 27⁰C for 85 to 95 minutes. The sides of the mould are now removed and the clips are carefully hooked on the machine with out causing any initial strain.

The pointer is set to zero, the machine is started and the two clips are pulled apart horizontally at a uniform speed of 50 +/- 2.5mm per minute. While the test is in operation, it is checked whether the sample is immersed in water at depth of at least 10mm. The distance, at which the bitumen thread of each specimen breaks, is recorded (in cm) to report as ductility value.

Results:

The distance stretched by the moving end of the specimen up to the point of breaking of thread measured in centimeters is recorded as ductility value.

Limits: The minimum ductility value of A35 & S35 grade bitumen is 50 cm at 27⁰C.

All other grades, the ductility value is 75 cm at 27⁰C.

DELETERIOUS CONTENTS OF SOILS.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:20:00 +0000

DELETERIOUS CONTENTS OF SOILS.

I. Determination of Total Soluble Sulphates by Volumetric Method: (IS : 2720 – Part – 27)

Object:

Determination of total soluble sulfate content of soil by Volumetric method.

Sample Preparation: Take about 100 grams of oven dried soil sample and sieve it in a 425 micron IS Sieve.

Preparation of Reagents:

1. Barium Chloride Solution (N/4): Dissolve 30.5 grams Barium chloride in one liter of distilled water.

2. Potassium Chromate Solution (N/4): Dissolve 24.275 grams of Potassium chromate in a small amount of distilled water. Add few drops of Silver Nitrate solution to it to remove any Chloride, filter and dilute to 250 ml.

3.Silver Nitrate Indicator: Dissolve 500 mg of Silver Nitrate in 100 ml of distilled water.

4.Dilute Solution of Ammonium Hydroxide: (Sp.Gr 0.888) Mix Ammonium Hydroxide and distilled water in the ratio of 1:2.

5.Concentrated Hydrochloric acid: Sp.Gr 1.11.

Test Procedure:

1. 10 grams of soil sample taken in to beaker.

2. Add 50 ml water, stir well, allow decanting and filtered.

3. Take 10 ml filtrate sample by pipette in a conical flask.

4. Make it slightly acidic by adding concentrated hydroelectric acid (i.e.: few drops) and heat to boiling.

5. Add Barium Chloride solution (N/4) from the Burnett till the precipitation is complete, measure the volume in ml and recorded it as ‘X’.

6. Neutralize the solution with Ammonium hydroxide (i.e.: few drops).

7. Tit rate the excess of Barium chloride against Potassium Chromatic solution(N/4), measure the volume in ml and recorded it as ‘Y’. the end point may be confirmed, if considered necessary, by using Silver nitrate solution as an external indicator.

Calculations:

Sulfates as Sodium Sulfate in Soil, percent by mass = 0.0177 x (X – Y)

II. DETERMINATION OF ORGANIC MATTER IN SOILS ( IS: 2720 – Part – 22)

Object:

Determination of total Organic matter in soils.

Sample Preparation:

1. Total weight of original soil sample (Oven dried) – W1 grams.

2. Sieve the sample on 10 mm IS sieve and weighed the passing material – W2 grams.

3. Then sieve the sample on 425 micron IS sieve and take the soil sample for the test – Approximately 5 grams – W3 grams.

Preparation of Reagents:

1. Potassium Dichromate Normal solution: Dissolve 49.035 grams of Potassium Dichromate in one liter of distilled water.

2. Ferrous Sulfate 0.5 N solution: Dissolve 140 grams of Ferrous Sulfate in 0.5 N Sulfuric acid to make one liter of solution (Add 14 ml of concentrated Sulphuric acid to distilled water to make one liter of solution for 0.5 N Sulfuric acid).

3. Concentrated Sulfuric acid: Sp.Gr 1.83.

4. Or tho Phosphoric acid: Sp.Gr 1.70 to 1.75.

5. Indicator: 0.25 grams of Sodium Diphemylamine-Sulphonate dissolved in 100 ml of distilled water.

Standardization of Ferrous Sulphate Solution:

1. Take 10 ml of Normal Potassium Dichromate solution in to 500 ml conical flask.

2. Add 20 ml concentrated Sulfuric acid and swirled and allowed to cool for some times.

3. Add 200 ml of distilled water, 10 ml of Or tho Phosphoric acid and 1ml of the Indicator and the mixture shall be shaking thoroughly.

4. Ferrous Sulfate solution added through Burnett in 0.5 ml increments, up to the solution changes from blue to green.

5. Add 0.5 ml Potassium Dichromate, then solution changing the color back to blue.

6. And then Ferrous Sulfate added drop by drop until the color of the solution changes from blue to green. Measure the total volume of Ferrous Sulfate solution in ml and recorded it as ‘X’.

Procedure:

1. Take 5 grams of soil sample of 425 micron IS sieve passing in 500 ml conical flask.

2. Add 10 ml of Potassium Dichromate solution.

3. Add 20 ml of concentrated Sulphuric acid and allowed to 30 minutes on a heat insulating surface like asbestos sheet.

4. Add 200 ml distilled water, 10 ml of Ortho Phosphoric acid, 1 ml of the Indicator and the mixture shall be shake vigorously.

5. Ferrous Sulphate solution added through burette in 0.5 ml increments, up to the solution changes from blue to green.

6. Add 0.5 ml Potassium Dichromate, then solution changing the color back to blue.

7. And then Ferrous Sulphate added drop by drop until the color of the solution changes from blue to green. Measure the total volume of Ferrous Sulphate solution in ml and recorded it as ‘Y’.

Calculations:

1. The Volume of Potassium Dichromate used to oxidize organic, V= 10.5(1 – Y/X).

2. Percentage of Organic Matter in soil = (0.67W2V) / (W1W3)

III. DETERMINATION OF CHLORIDE AND SALINITY IN SOILS

Object:

Determination of total Organic matter in soils.

Sample Preparation:

1. Take the oven dried soil sample and sieve it on 2 mm IS sieve.

2. Take 50 grams of 2mm passing material in conical flask and add the distilled water with 1:5 ratio, allowed to 16 hrs, so that the salts are extracted by the distilled water completely.

Preparation of Reagents:

1. Chloride free distilled water.

2. Potassium Chromate – color Indicator.

3. Standard Silver Nitrate (0.0141N / 0.0156N): Dissolved 2.395 grams Silver Nitrate in one liter of hot distilled water to prepare 0.0141N solution. Alternatively, dissolve 2.65 grams of Silver Nitrate in one liter of hot distilled water to prepare 0.0156N solution.

Procedure:

1. Take 25 ml of filtered sample in a conical flask.

2. Adjust the PH in the range of 7 to 8 by adding Sulphuric acid or Sodium Hydroxide solution.

3. Add 1 ml of Potassium Chromate – Yellow color develops.

4. Take 0.0156N Silver Nitrate solution in burette and titrate till brick red color develops. Measure the volume in ml and recorded it as ‘X’.

Calculations:

1. Chloride(mg/l or ppm), Y = (X x 35.46 x 1000 x 0.0156) / (ml of sample taken)

2. Salinity (ppt or gms/lt) = 0.03 + 1.806 x Chlorides in g/lt.

3. Total Chlorides in soil sample = 5 x Y.

DELETERIOUS CONTENT OF AGGREGATES. ( IS : 2386 – PART – 2 ) I. DETERMINATION OF CLAY LUMPS:

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 09:15:00 +0000

DELETERIOUS CONTENT OF AGGREGATES.

( IS : 2386 – PART – 2 )

I. DETERMINATION OF CLAY LUMPS:

Apparatus:

1) Balance – sensitive to 0.001 g, 2) Containers – size and shape that will permit the spreading of the sample on the bottom in a thin layer, 3) Sieves – conforming to IS : 460-1962.

Sampling:

Samples shall be obtained by quartering or by the use of a sampler, from a representative sample selected from the material to be tested. They shall be handled in such a manner as to avoid breaking up clay lumps, which may be present. Samples shall be dried to constant weight at a temperature not exceeding 110 ⁰C.

Samples of fine aggregate shall consist of particles coarser than 1.18 mm IS sieve and shall weigh not less than 100 g.

Samples of coarse aggregate shall be separated into different sizes using 4.75mm, 10mm, 20mm and 40mm IS sieves. The weight of the sample for different sizes shall be not less than those indicated below:

Size of Particles Marking Weight of Samples Min (gm)

up the Sample (mm)

4.75 to 10 1000

10 to 20 2000

20 to 40 3000

over 40 5000

In the case of mixtures of fine and coarse aggregates, the material shall be separated into two sizes on 4.75 mm IS sieve, and the samples of fine and coarse aggregates shall be prepared as described above.

Procedure:

The sample shall be spread in a thin layer on the bottom of the container and examined for clay lumps. Any particles, which can be broken into finely divided particles with the fingers, shall be classified as clay lumps. After all discernible clay lumps have been broken, the residue from the clay lumps shall be removed by the use of sieves indicated below:

Size Particles marking up Size of sieves for sieving residue of

the Sample clay Lumps

Fine aggregate (Retained on 1.18 mm) 850 micron

4.75 to 10 2.36 mm

10 to 20 4.75 mm

20 to 40 4.75 mm

Over 40 mm 4.75 mm

Calculations:

The percentage of clay lumps shall be calculated to the nearest 0.1 percent in accordance with the following formula:

(W – R)

L = ------------- X 100

Where, L = percentage of clay lumps.

W = weight of sample.

R = weight of sample after removal of clay lumps.

II. DETERMINATION OF CLAY, FINE SILT AND FINE DUST.

Apparatus:

1) A watertight screw-topped glass jar of dimensions similar to a 1-kg fruit-preserving jar, 2) A device for rotating the jar about its axis, with this axis horizontal, at a speed of 80 +/- 20 rev/min, 3) A sedimentation pipette of the And reason type of approximately 25 ml capacity. This consists mainly of a pipette fitted at the top with a two way tap and held rigidly in a clamp which can be raised or lowered as required, and which is fitted with a scale from which the changes in height of the pipette can be read, 4) A 1000 ml measuring cylinder, 5) A scale or balance of capacity not less than 10 kg, readable and accurate to one gram, 6) A scale or balance of capacity not less than 250 g, readable and accurate to 0.001 g, 7) A well ventilated oven, thermostatically controlled, to maintain a temperature of 100 to 110 ⁰C.

Chemicals:

A solution containing 8 g of sodium oxalate per liter of distilled water shall be taken. For use, this stock solution is diluted with distilled water to one tenth (that is 100 ml diluted with distilled water to one liter).

Test sample:

The sample for test shall be prepared from the main sample taking particular care that the test sample contains a correct proportion of the finer material. The amount of sample taken for test shall be in accordance with below table.

Maximum Size Present Approximate Weight of sample for test

in substantial (kg)

63 to 25 6

20 to 12.5 1

10 to 6.3 0.5

4.75 or smaller 0.3

All in aggregates shall be separated into fine and coarse fractions by sieving on a 4.75 mm IS sieve and the two samples so obtained shall be tested separately.

Procedure:

Method for fine aggregate: Approximately 300 g of the sample in the air dry condition, passing the 4.75 mm IS sieve, shall be weighed and placed in the screw topped glass jar, together with 300 ml of the diluted sodium oxalate solution. The rubber washer and cap shall be fixed, care being taken to ensure water tightness. The jar shall then be rotated about its long axis, with this axis horizontal, at a speed of 80 +/- 20 rev/min for a period of 15 minutes. At the end of 15 minutes, the suspension shall be poured into the 1000 ml measuring cylinder and the residue washed by gentle swirling and decantation of successive 150 ml portions of sodium oxalate solution, the washings being added to the cylinder until the volume is made up to 1000 ml. The determination shall be completed as described below.

Method for coarse aggregate: The weighed sample shall be placed in a suitable container, covered with a measured volume of sodium oxalate solution (0.8 g per liter), agitated vigorously to remove all adherent fine material and the liquid suspension transferred to the 1000 ml measuring cylinder. This process shall be repeated as necessary until all clayey material has been transferred to the cylinder. The volume shall be made up to 1000 ml with sodium oxalate solution and the determination completed as described below.

The suspension in the measuring cylinder shall be thoroughly mixed by inversion and the tube and contents immediately placed in position under the pipette. The pipette shall then be gently lowered until the tip touches the surface of the liquid, and then lowered a further 10 cm into the liquid. Three minutes after placing the tube in position, the pipette and the bore of tap shall be filled by opening and applying gentle suction. A small surplus may be drawn up into the bulb between tap and tube, but this shall be allowed to run away and any solid matter shall be washed out with distilled water from top end. The pipette shall then be removed from the measuring cylinder and its contents run into a weighed container, any adherent solids being washed into the container by distilled water

from top end. The contents of the container shall be dried at 100 to 110⁰C to constant weight, cooled and weighed.

Calculations: The proportion of fine silt and clay or fine dust shall then be calculated from the following formula:

100 1000 W2

Percentage of clay and fine silt or fine dust = ----- ( ---------- - 0.8 )

W1 V

Where, W1= weight in g of the original sample, W2= weight in g of the dried residue, V= volume in ml of the pipette & 0.8 = weight in g of sodium oxalate in one liter of the diluted solution.

III.DETERMINATION OF LIGHT-WEIGHT PIECES.

Apparatus:

1) Balances – for weighing fine aggregates, a balance having a capacity of not less than 500 g, sensitive to at least 0.1 g; for weighing coarse aggregates, a balance having a capacity of not less than 5000 g, sensitive to at least 1 g.

2) Containers – containers suitable for drying the aggregate sample, and containers suitable for holding the heavy liquid during the sink-float separation.

3) Skimmer – a piece of 300-micron sieve cloth of suitable size and shape for separating the floating pieces from the heavy liquid.

4) Hot-plate or oven.

Heavy liquid: The heavy liquid shall consist of a mixture of carbon tetra chloride, and 1, 1, 2, 2-tetrabromoethane, chloroform, and monobromobenzene, or bromoform and benzene, in such proportions that the desired specific gravity will be obtained. Bromotrichloromethane may be used as a heavy liquid having a specific gravity of 2.00. The specific gravity shall be maintained within +/- 0.01 of the specified value at all times during the test.

The approximate volumes of materials to be combined to produce a mixture of the desired specific gravity may be computed from the following specific gravitates of the different liquids:

Liquid specific Gravity

1,1,2,2 2.97

Ben zen 0.88

Bromofrom 2.88

carbon tetra chloride 1.58

Monobromo benzen 1.49

For determining coal and lignite, the heavy liquid used shall have a specific gravity of 2.00 +/- 0.01.

Test Sample: The minimum size of test sample shall be as follows:

Maximum size of aggregate (mm) Minimum Weight of Samples (gm)

6.3 (fine aggregate) 200

20 3000

40 5000

80 10000

Procedure:

1) Fine aggregate: Allow the dried sample of fine aggregate to cool to room temperature and then sieve over a 300-micron IS sieve until less than one percent of the retained material passes the sieve in one minute of continuous sieving. Weigh the material coarser than the 300-micron IS sieve to the nearest 0.1 g; then introduce it into the heavy liquid in a suitable container, the volume of liquid being at least three times the absolute volume of the aggregate. Pour the liquid off into a second container; passing it through the skimmer and taking care that only the floating pieces are poured off with the liquid and that none of the sand is decanted onto the skimmer. Return to the first container the liquid that has been collected in the second container and, after further agitation of the sample by stirring, repeat the decanting process just described until the sample is free of floating pieces. Wash the decanted pieces contained on the skimmer in carbon tetrachloride, until the heavy liquid is removed, and then dry. The pieces will dry very quickly, but may be placed in an oven at 105⁰C for a few minutes if desired. Brush the dry decanted pieces from the skimmer onto the balance pan and determine the weight to the nearest 0.1 g.

2) Coarse aggregate: Allow the dried sample of coarse aggregate to cool to room temperature and sieve over a 4.75 mm IS sieve. Weigh the material coarser than the 4.75 mm IS sieve to the nearest 1 g; then introduce it into the heavy liquid in a suitable container, the volume of the liquid being at least three times the absolute volume of the aggregate. Using the skimmer, remove the pieces that rise to the surface, and save them. Repeatedly agitate the remaining pieces and remove the floating pieces until no additional pieces rise to the surface. Wash the decanted pieces in carbon tetra chloride until all of the heavy liquid is removed, and allow to dry. Determine the weight of the decanted pieces to the nearest 1-gram.

Calculations: Calculate the percentage of lightweight pieces as follows:

For fine aggregate: L = (W1/W2)x100

For coarse aggregate: L = (W1/W3)x100

Where, L = percentage of lightweight pieces, W1 = dry weight in g, of decanted pieces, W2 = dry weight in g, of portion of sample coarser than 300-micron IS sieve & W3 = dry weight in g, of portion of sample coarser than 4.75 mm IS sieve.

DETERMINATION OF SOFT PARTICLES.

Apparatus: The apparatus shall consist of a brass rod, having a Rockwell hardness of 65 RHB to 75 RHB. A brass rod of about 1.6 mm diameter and of proper hardness inserted into the wood shaft of an ordinary lead pencil is a convent tool for field or laboratory use.

Test Sample: Aggregates for the test shall consist of material from which the sizes finer than the 10 mm IS sieve have been removed. The sample tested shall be of such size that it will yield not less than the following amount of the different sizes, which shall be available in amounts of 10 percent or more:

Sieve size (mm) Sample Weight (gms)

10 to 12.5 200

12.5 to 20 600

20 to 25 1500

25 to 40 4500

40 to 50 12000

Procedure:

Each particle of aggregate under test shall be scratched with the brass rod with a small amount of pressure (about 1 kg). Particles are considered to be soft if during the scratching process, a groove is made in them without deposition of metal from the brass rod or if separate particles are detached from the rock mass.

Calculations: The report shall include the following information.

a) Weight and number of particles of each size of each sample tested with the brass rod.

b) Weight and number of particles of each size of each sample classified as soft in the test.

c) Percentage of test sample classified as soft by weight and by number of particles.

d) Weighed average percentage of soft particles calculated from percentage in item (c) and based on the grading of sample of aggregate received for testing.

AGGREGATE CRUSHING VALUE TEST.

noreply@blogger.com (Civil Engineering.com) — Sun, 19 Jan 2020 08:22:00 +0000

AGGREGATE CRUSHING VALUE TEST.

( IS : 2386 – PART – 4 )

INTRODUCTION:

The principal mechanical properties required in stones are (i) satisfactory resistance to crushing under the roller during construction and (ii) adequate resistance to surface abrasion under traffic. Aggregates used in road construction, should be strong enough to resist crushing under traffic wheel loads. If the aggregates are weak, the stability of the pavement structure is likely to be adversely affected. The strength of coarse aggregates is assessed by aggregates crushing test. The aggregate crushing value provides a relative measure of resistance to crushing under a gradually applied compressive load. To achieve a high quality of pavement, aggregate possessing low aggregate crushing value should be preferred

Object:

To determine the aggregate crushing value by compressive testing machine.

Apparatus:

a) Steel cylinder with open ends, and internal diameter 152 mm, square base plate, plunger having a piston of diameter 150 mm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder.

b) Cylindrical measure having internal diameter of 115 mm and height 180 mm.

c) Steel tamping rod with one rounded end, having a diameter of 16 mm and length 450 to 600 mm.

d) Balance of capacity 3 kg with accuracy up to 1 gm.

e) Compressive testing machine capable of applying load of 40 tonnes, at a uniform rate of loading of 4 tonnes per minute.

Procedure:

The aggregate passing 12.5 mm IS sieve and retained on 10 mm IS sieve is selected for standard test. The aggregate should be in surface dry condition before testing. The aggregate may be dried by heating at a temperature 100 ⁰C to 110 ⁰C for a period of 4 hours and is tested after being cooled to room temperature.

The cylindrical measure is filled by the test sample of aggregate in three layers of approximately equal depth, each layer being tamped 25 times by the rounded end of the tamping rod. After the third layer is tamped, using the tamping rod as a straight edge levels off the aggregate at the top of the cylindrical measure. About 6.5 kg of aggregate is required for preparing two test samples. The test sample thus taken is then weighed. The same weight of the sample is taken in the repeat test.

The cylinder of the test apparatus is placed in position on the base plate; one third of the test sample is placed in this cylinder and tamped 25 times by the tamping rod. Similarly, the other two parts of the test specimen are added, each layer being subjected to 25 blows. The total depth of the material in the cylinder after tamping shall however be 100 mm. The surface of the aggregates is leveled and the plunger inserted so that it rests on this surface in level position. The cylinder with the test sample and the plunger in position is placed on compression testing machine. Load is then applied through the plunger at a uniform rate of 4 tonnes per minute until the total load is 40 tonnes, and then the load is released. Aggregates including the crushed portion are removed from the cylinder and sieved on a 2.36 mm IS sieve. The material, which passes this sieve, is collected.

The above crushing test is repeated on second sample of the same weight in accordance with above test procedure. Thus two tests are made for the same specimen for taking an average value.

Calculation:

The aggregate crushing value is defined, as a ratio of the weight of fines passing the specified IS sieve to the total weight of the sample expressed as a percentage.

100 W2 Where, W1 = Total weight of dry sample.

Aggregate crushing value = W1 W2 = Weight of the portion of crushed material passing 2.36 mm IS sieve.

Results: The mean of the crushing value obtained in the two tests is reported as the aggregate crushing value.

Limits: The aggregate crushing value for cement concrete pavement shall not exceed 30%.

The aggregate crushing value for wearing surfaces shall not exceed 45%.