Urban News

The Hindu 20.01.2010

New concrete promises to increase durability

Staff Reporter

VISAKHAPATNAM: A new concrete developed by the Institute of Solid Waste Research and Ecological Balance and Ecological Balance (INSWAREB) here promises to increase the durability of concrete apart from addressing sustainability issues.

Christened ‘No-Aggregate Concrete (NAC)’, the mixture doesn’t contain stone (coarse aggregate) as in the case of conventional concrete. N. Bhanumathidas and Kalidas of INSWAREB claim that preliminary studies have proved that the durability of concrete could be increased by 10 to 20 times with the use of NAC.

The transition zone i.e., the ‘zone of bond’ between the cement matrix and stone (coarse aggregate) results in accumulation of free lime and formation of low density crystals of lime that develop weak links and micro cracks due to tensile shrinkage. Dr. Bhanumathidas and Kalidas feel that avoiding coarse aggregate in concrete, without sacrificing the performance requirements, gives a new definition to concrete that is devoid of transition zone. Fine and coarse aggregate are added to cement to render workability and application.

The researchers claim that the mixture developed at INSWAREB labs doesn’t contain coarse aggregate but uses fly ash as pozzolanic binder and micro aggregate nullifying the role of coarse aggregate. They say the strength of NAC ranges between 40 MPa and 80 MPa, which is two to four times the strength of conventional concrete thus saving money and material.

“Though density of this concrete is around 1,800 kg/cu. m as against 2,400 kg/cu. m. for conventional concrete, the increased strength is achieved to due to microstructure properties and better bonding. The mixture contains cement, fly ash, additives and chemical admixtures,” Mr. Kalidas said.

The differential density would open up new vistas in designing structures resistant to earthquakes. Avoiding the use of coarse aggregate conserves natural stones and saves hillocks and hills. “A 10-foot diameter dome would be constructed by INSWAREB at Sheelanagar for demonstration of NAC. The product developed would be sent to the Ramco Research and Development Centre in Chennai for micro structure studies,” Mr. Kalidas added.

The Hindu 20.01.2010

New building rules come into force

Special Correspondent

THIRUVANANTHAPURAM: The government has brought into force the revised building rules in the State by reducing the coverage and floor area ratio and increasing the number of parking lots and extent of open space.

Local Administration Minister Paloli Mohammed Kutty said in a release here on Tuesday that restrictions had been imposed on the construction of multi-storeyed buildings. The coverage of residential apartments has been reduced to 1.5. On remitting an additional fee, this would be increased up to 2.75.

Curbs have been imposed on constructing multi-storeyed buildings close to narrow roads. As many as 100 units will be permitted on sites which have an access of 12-metre width. For constructing more than 100 units, the access should be 15 metre wide. A seven-metre road is mandatory for constructing a four-storeyed building.

While constructing residential apartments, a 100-sq.m. apartment should have one car parking facility. This has been increased in the case of hotels. Residential flats and apartments should set apart 30 per cent space for parking visitors vehicles.

Tackling emergencies

All multi-storeyed buildings should provide 5-metre open space around them so that fire-tenders can move freely in the event of an emergency. Solar water heaters should be installed in lodges, hospitals, marriage halls and residential apartments.

All details of construction, including the name of the developer and construction permit, should be displayed at the construction sites. Land developers should furnish details of approval for layout too. Permission of the immediate resident should be secured for scooping the plot beyond the prescribed limit.

The developer will have to compensate for the loss, if any, incurred due to piling. A qualified engineer should always be present at the sites. Safety norms too have been laid in the rules.