Demonstrates suitability of bottom ash as construction material

At a time when the riverbed sand is getting scarce and its price fast rising, the Neyveli Lignite Corporation has evolved a technology to use bottom ash, a residue being collected from the thermal power stations, as substitute for sand.

After three-and-half-years of relentless research the NLC has demonstrated the suitability of bottom ash as a construction material that has the potential to replace sand.

To demonstrate the utility of bottom ash the NLC has erected an experimental building in an area of 920-sq.ft, built at a cost of Rs. 15 lakh at the pre-casting yard on its premises.

Inaugurating the building on Wednesday, NLC Chairman-cum-Managing Director B. Surender Mohan said that it was the outcome of the collaborative efforts with the VIT University, Vellore, under the industry — institute initiative.

The civil engineers of the NLC led by general managers S. Santhanam and R. Ramakrishnan who worked in tandem with academicians of VIT University led by A.S. Santhi and G. Mohan Ganesh had made it possible after having worked on the Rs. 45.46-lakh project for the past three-and-half years, ever since the Memorandum of Understanding was signed on December 3, 2010 in this regard.

The Chairman complimented the engineers and the academicians for their tireless efforts in finding a right substitute for sand. Annually the Thermal Power Station-I Expansion was generating 25,000 tonnes of bottom ash. (It is usually disposed of on the mine bed).

Now with the arrival of the new technology the entire quantum of bottom ash being obtained from the TPS-I Expansion could be put to use for manufacture of concrete blocks that would meet the demand for domestic consumption.

Through this measure the NLC could save about Rs. 1.5 crore a year. In the concrete portions of the experimental building, such as roofing, plinth beam, lintel and sunshade, bottom ash and sand were used in the ratio of 50:50. However, in the preparation of concrete blocks sand was totally dispensed with by combining the following materials — cement, fly ash, bottom ash and chips in the ratio of 1:0.5:3.5:3 respectively.

It was proved that these blocks had better compressive strength and less water absorbing capacity than the conventional bricks.

The NLC sources said that the bottom ash would fulfil the domestic requirement because many structures were constantly coming up on the premises. Two types of ash deposits — fly ash and bottom ash — were being collected from the boilers of the thermal power station; the first one mostly from the sides and upper portions of the boilers and the second from the bottom of boilers.

“Fly ash is a finer material that finds elaborate use in the brick and cement industry, whereas bottom ash is a coarse material having grains similar to or slightly bigger than that of sand. By putting both forms of ashes to productive use the NLC has now become eminently equipped to protect environment,” the sources added.

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