Fly ash has a new story to tell

The country’s largest power generation company, NTPC, has been taking its sustainability effort seriously. Developing geopolymer and nano aggregates from residual fly ash for use in construction of roads and houses is a manifestation of this.

With an installed capacity of over 64,880 MW, and nearly 20,000 MW under construction, NTPC has its task cut out in decarbonisation and reduction of gas emissions.

India produces about 258 million tonnes of fly ash per annum, a by-product of coal-fired power plants. Of this, about 78 per cent is utilised and the balance remains in ash dykes. NTPC intends to transform the fly ash it produces into a revenue generating by-product.

By reusing the 8,000 tonnes of ash produced daily at the NTPC’s Ramagundam plant, it is minimising fugitive emissions from ash ponds. Over the last three years, the station has achieved over 100 per cent ash utilisation. CV Anand, Executive Director of NTPC Southern Region, says, “NTPC has developed and deployed geopolymer coarse aggregates and nano concrete aggregates. It has constructed a 1.45-km cement-free, fly-ash-based geopolymer road inside the Telangana Super Thermal Power Project in Telangana.” The company is also supplying the aggregates to the National Highway Authority of India.

NTPC has launched a research project for the generation of geopolymer aggregate using more than 90 per cent fly ash. Tests at the National Council for Cement and Building Materials in Hyderabad show these coarse aggregates can be used in construction of buildings.

Anand says, “This aggregate does not require any cement for using it in concrete.” It can reduce carbon emission and water consumption, he adds.

The country’s infrastructure development requires an estimated 2,000 million tonnes of aggregates a year.

At the NTPC Simhadri plant, close to Visakhapatnam, a model building has been developed using nano concrete aggregate. Fly ash is also used as a micro-nutrient and for soil amendment in agriculture.

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