all about construction

What is Ductal?

2010-01-04T18:06:00.000-08:00

What is Ductal?

Few Years back in 2006; researchers at Iowa State University have developed a new type of concrete that is much stronger than conventional concrete. It can withstand pressures up to 595,000 pounds — more than the weight of seven semi trucks.

A new kind of concrete called Ductal that might allow bridges to hold more weight and last longer. Although it is 10 times more expensive than traditional materials but stronger and virtually impermeable, helping bridges become more durable.

The researchers conducted a load-bearing capacity test using a 71-foot beam made out the new concrete. They applied increasing amounts of hydraulic pressure to the top of the beam to see how much it could withstand before breaking. It finally broke with a loud pop at 595,000 pounds. The ultra-high performance concrete is made from sand, cement, water and small steel fibers. Standard concrete uses coarser materials. The new concrete is specifically engineered to include finer materials and steel fibers, making it denser and stronger.

Facts about construction in India

2010-01-04T09:47:00.001-08:00

Facts About Construction In India

# Sardar Sarovar Dam being executed by the group is the third largest in the world for volume of chilled concrete to be placed -nearly 7 million cum.

# Indira Sagar a 1000 MW Power house is the second largest surface power house in the country.

# Nathpa Jhakri a 1500 MW Power House is the largest underground power house in India.

# Tehri Dam is the third tallest rockfill dam in the world, and the largest in Asia invloving placement of over 25 million cum of all types of fill material.

# Baglihar Hydroelectric project involved construction of 30km of project road along with three bridges.

# Brahmaputra Guide Bund completed in a record time of 7 months.

# Baspa-II and Chamera-II projects involved continuous concrete shuttering for tunnel lining which is used for the first time in the country.

# Teesta V project has been provided with Jet Grouting curtain is being provided below the coffer dams for the first time in India.

# Alimineti Madhva Reddy Irrigation project is the longest underground face to face tunnel in the world.

Concrete Maturity Tester

2009-12-29T10:24:00.001-08:00

Maturity Testing Primer:

When concrete hardens (cures), it gives off heat proportional to its curing rate. By learning how much heat is released, an accurate estimate of the strength can be determined.

Generally, concrete in a structure cures at a MUCH faster rate than concrete in a test cylinder. This is due to the much larger mass of the structure, and better hydration which aids curing. When determining the early-age strength of cast-in-place concrete, reliance on test cylinders can lead to problems. For example, if test cylinders are cured at a lower temperature than the structure, the cylinders would underestimate the strength of the slab, which means that critical construction operations are delayed unnecessarily. Or conversely, if the deck is cooler than the cylinders, the cylinders would overestimate the strength, a clear safety concern.

Maturity testing monitors the curing of the structure and compares it to the cylinder, to more accurately track strength gain in the structure, improving both safety and construction operations.

Maturity Testing has been a recognized ASTM Standard practice (C1074) for over 20 years.

What is BIOCEMENT ?

2009-12-29T07:54:00.000-08:00

Thanks to Varenyam Achal for publishing these research

. Microbes are microscopic organisms such as fungi (which include yeasts), bacteria and viruses. They not only provide the foundation for much of the basic research involved in biotechnology, they help to create durable building materials and structures.

Recently I(Varenyam Achal) discovered and improved few bacterial species which were able to precipitate calcite at higher rate and eventually this process lead to improved compressive strength, reduced permeability and low corrosion rate of reinforcement.

Biocement, a self-healing material to enhance durability of building structures and conservation of cultural heritages

All building materials are porous. This porosity of building material along with ingress of moisture and other harmful chemicals such as acids, chlorides and sulfates affect the material and seriously reduce their strength and life. An additive that seals the pores and cracks and thus reduces the permeability of the structure would immensely improve its life. Conventionally, a variety of sealing agents such as latex emulsions and epoxies etc.; and surface treatments with water repellents such as silanes or siloxanes are used to enhance the durability of the concrete structures. However, they suffer from serious limitations of incompatible interfaces, susceptibility to ultraviolet radiations, unstable molecular structure and high cost. They also emanate toxic gases.
In order to overcome the shortcomings of conventional sealing agents, materials with self-healing capability can be used effectively. Use of urease producing microbes addresses these problems effectively, as these continue to survive and grow within the concrete structure after the initial use. Urease helps in mineralization of calcium carbonate, by hydrolyzing urea present in the environment. It releases carbon dioxide from urea that combines with calcium ions resulting in deposition of calcium carbonate in the form of calcite. Due to urease activity, bacteria are able to use urea as a sole nitrogen source and produce ammonia, which increases the pH in the proximal environment, causing Ca2+ and CO32- to precipitate as CaCO3. These unique properties make it particularly suitable for many applications in civil engineering (concrete structures, plasters, mortars, prefabricated elements, refractory elements, bricks, natural stones, etc.)

A microbial additive that helps in calcite precipitation with urease would enhance durability of building materials as well preserve the cultural heritage.

Some tips on Crack control in concrete

2009-12-27T06:47:00.000-08:00

Different types of cracks includes

Plastic Shrinkage Cracks
Plastic Settlement Cracks
Early thermal contraction cracks
Crazing
Drying Shrinkage
Construction Movement
Accident Overload

Click here for the detailed report on crack control - pdf file

Welcome

2009-12-26T21:26:00.000-08:00

Welcome all to the new blog site on construction.