PL Bongirwar is the one of the first few government engineers in the country to have used fly ash in pavement quality concrete in southern Maharashtra.
In the year 2003, it was a very bold decision for a government road project to allow use of fly ash. We allowed it in the tender itself, so that there would not be a problem later on. In order to encourage the use of flay ash, we incentivised the contractor. It was suggested that if there is a saving of Rs 1, he should pass on to us only 20 paise.
Surprisingly, the idea clicked. In the design, L&T was using 270 kg of OPC, 110 kg of fly ash and could get results of M 60, whereas we wanted only M 40. Later on, I was criticised, but the important part is the idea of using fly ash in pavement-quality concrete (PQC) got recognition. Today everywhere in the country, fly ash is used in PQC.
Many structural engineers are not using fly ash concrete for structural grade of concrete, mainly due to apprehensions of corrosion of re-bars, but the apprehension is ill-founded. There are a good number of research papers available which say that concrete produced with fly ash is more watertight.
If we want to increase the use of fly ash, the best option is to install efficient air-separators with a capacity of maximum 500 kg to 1 tonne, costing around Rs 9 to 10 lakh. You will get good quality of fly ash separated out. Look at what Dirk is doing at Nasik. They are able to produce quality fly ash in four different varieties and get a rate of Rs 1,800 to Rs 2,600 per tonne.
In fly ash, you need particles less than 45 microns. Such narrow range of particles is possible only if we use separators.
The other aspect which is forgotten is the landed cost of fly ash. It has to be less than Rs 3 per kg. Anything you incur on transportation is around Rs 1 per kg for 150 km; cost of fly ash is around Rs 2 per kg. These rates will be viable only if fly ash is transported in the range of 100 to 150 km radius from its source, beyond which cost of fly ash will be unattractive and no one would like to use it.
(PL Bongirwar holds M Tech and B Tech degrees from IIT-Bombay. He was in-charge of the prestigious Mumbai-Pune Expressway; when he was Joint Managing Director of MSRDC he constructed 50 flyovers in Mumbai and built 29 ROBs across the state. He evolved a new innovative design and construction methodology. He is passionate about the use of fly ash in concrete. Bongirwar is presently working with L&T as an advisor).
MAHAGENCO produces around 34,000 tonnes of fly ash daily from its various thermal power stations. Vijay Singh, Director-Operations, shares his views on the usability of fly ash.
The main function of MAHAGENCO is to produce power. While producing power, we get fly ash as a by-product.
The present generation of fly ash is around 34,000 tonnes per day from various thermal power stations. Out of the total generation, we are able to use about 60 to 65 per cent of fly ash for various applications.
MAHAGENCO as an entity is not into selling of fly ash, but there is a policy decision to form joint ventures for implementing such decisions for effective use of fly ash. Whatever we do regarding value-addition to fly ash will be through joint ventures or through a special purpose vehicle. Our fly ash mainly goes into cement and production of concrete, brick-making, etc. We conducted a few experiments jointly with agricultural universities and improvement in the crop yield was observed. Right now a major portion of fly ash is going for the construction road work of NH 6, from Akola to Dhulia. There it is going for soling purpose. But this kind of use is for limited time. Regarding exports, only cenospheres have a potential of getting exported. They also give better realisation. However, the quantity of cenospheres is limited.