Too much cement can make metro rail structures vulnerable: expert

C Shivakumar

Chennai:

India is ignorant of the use of fly ash in concrete mix and projects such as Chennai Metro Rail rely on using only cement and don’t permit use of fly ash which could result in structures developing cracks, according to an expert.

Delivering the G S Ramaswamy Memorial Lecture here to mark the 49^th foundation day of CSIR-SERC, former deputy managing director of Gammon India S A Reddi said that use of too much cement could result in increased cracking due to shrinkage and thermal effects.

He said engineers as well as builders feel that use of too much cement in the building projects could increase the strength of the building. But they are wrong. Even the airport expansion project is being done without the use of fly ash, he said.

He said that on an average India uses 100 million tonnes of cement a year for concrete mix. This could be reduced by 30 million tones if the construction sector uses fly ash. He said this could also improve the life span of a building in India which uses only cement.

He said that as per the Euro code the first part of any design is focused on the life of structure. While the life of a Euro structure is anyway between 100 to 120 years, the life of an Indian concrete structure that is totally dependent on cement is 50 years.

He also highlighted that Indian construction engineers are unable to design a mix with less cement. Quoting a published paper, Reddi said that India use cement content 30 per cent more than what is being used in developed countries.

He said may developed countries are replacing 70 per cent of cement with fly ash. But then is Indian fly ash of good quality. Reddi said that fly ash from power station is not fit for use in concrete and India uses unprocessed fly ash.

The issue is India is ignorant of the use of processed fly ash and has only one plant in Nashik to process it. Many of the engineers use the fly ash without cleaning, he said.

He said that cement produced in India is also not of the good quality when compared to Europe. “Indian cement is one grade less when compared to the cement used in Europe,” says Reddi.