Cyrus Pithawala, Director Engineering, Hiranandani Constructions
When it comes to using fly ash for construction, Cyrus Pithawala is the first name that comes to our mind. He is one of the pioneers in this field and has played a key role in communicating and establishing the benefits of fly ash blending in the industry. With years of research and experimentation on fly ash blends, he has arrived at the just right formula for the mix. He shares his approach to using fly ash with ICR. Excerpts from the interaction.
Do you use fly ash in your cement/concrete blends and to what extent?
We use fly ash extensively in all our projects. Now fly ash has become one of the important ingredients for our concrete. In fact even when we outsource concrete through RMC plant, we insist that concrete must have fly ash.
The extent of fly ash content depends on many factors like the quality of fly ash, compressive strength of concrete (especially early strength concrete), and mixing efficiency of concrete mixers. Normally fly ash content varies from 20 per cent to 40 per cent.
What are the benefits of blending fly ash in cement?
Blending of fly ash has many benefits especially when used in coastal environment like Mumbai. Most important is the improvement in durability due to secondary hydration process. Other benefits include:
How do you grade the quality of fly ash?
The quality of fly ash is primarily defined by its fineness. Finer fly ash is more reactive and is thus a preferred choice, especially for making high grade concrete. However, one has to ensure consistency in fineness of fly ash, which can be tested on site using a 45-micron sieve. One must be aware that pond ash shall not be used in concrete. Lastly, fly ash must be checked for its fineness, and must be rated as per Blaines Index, which gives the surface area and loss on ignition at a good reputed laboratory on a regular basis.
How is the availability of good quality fly ash in the country?
Quality of fly ash available in India is not consistent. But there are few sources/suppliers that do ensure supply of good quality of fly ash. Fly ash is basically a by-product of thermal power plants and proper system shall be set up to segregate fly ash of different fineness. Choosing fly ash of the right fineness for concrete making is very important and it depends on the final result that one intends to obtain. Hence the client shall be very alert in testing quality of fly ash on regular basis.
Which are your noteworthy projects where fly ash was used in significant quantity?
As I mentioned earlier, we are using fly ash in all our projects in Mumbai, Chennai and Bangalore. Basically, we are the pioneers for use of fly ash, especially in Mumbai.
Is the industry fully aware of these benefits? What would be your message to the construction community on this?
I would like to say that we must not look at fly ash as just a substitute to reduce cement content and consequently the cost. One has to understand wide range of advantages offered by fly ash. At the same time one has to have proper infrastructure and must have the right Quality Assurance systems in place for procuring, storing, mixing and curing of fly ash concrete. At times people simply add fly ash in concrete without properly understanding the science of concrete mix design and thus do not get the required benefits of fly ash.
Surprisingly, the construction industry is yet not fully aware of the advantages of fly ash. The industry is not yet certain about the quality of fly ash available in India and is neither well equipped to analyse it properly. If used extensively, fly ash can actually improve the quality of concrete, by making it more homogenous.
In conclusion, construction industry must insist on good quality fly ash for which efforts from all the sectors like fly ash producers, suppliers and end users is required.