Ultrafine Materials: Changing the Dynamics of Concrete
Would shifting to environment-friendly concrete be financially sustainable?
All products and services have two major inbuilt costs: the cost of energy required to process it, and the cost of energy to transport it to the market. Apart from this, there are many by-products produced during the manufacturing process, which are mostly pollutants, and incur cost for their disposal, and find their utility in the manufacture of concrete. These by-products incur no cost for the energy used in production, but only the cost of energy needed for their transportation. Thus, the correct indicator for environmentally friendly concrete is basically concrete, which is financially sustainable.
The acceptance of the recent trend of using eco-friendly concrete is still very low; it has not picked up the way it should have. This is because the construction industry is rule-book driven, which means that unless specified and documented, concrete specifications will not be changed.
Also, the specifications are not performance-based, but are prescriptive, wherein the minimum cement, maximum replacement etc. are specified along with just the performance for strength, but there is no mention of durability or sustainability parameters. These documents do not warrant against usage of more environmentally friendly concrete, but it is also the interpretation of these specifications that leads to slow acceptance.
To change this situation, educating the specifiers and the designers will be required. Manufacturers and customers still haven’t understood the importance of environment friendly concrete, and what profits and benefits are in store for them by using this concrete. Manufacturers are driven by customers and customers by the prescriptive specifications, which do not change so easily.
Why is Greencrete by RDC Concrete so popular amongst the designers?
Greencrete is made using selected cementitious materials judiciously such that the cost of concrete is minimum for the specifications of strength. The choice of materials for Greencrete are driven by local conditions, as the closest available material which can give the highest performance per unit cost. As said earlier, the cost of concrete is the best indicator of its environmental friendliness or sustainability. Not many designers are yet aware of such concrete, unfortunately, but few of them have started specifying this concrete for their projects - the reason could be the cost or its sustainability factor. Though green concrete may not find its optimum use everywhere, today almost 50% of conventional concrete can be replaced by Greencrete.
What R&D is being conducted in India for developing sustainable solutions for environment friendly construction?
R&D is being done in national institutes for developing sustainable solutions in construction. These include developing materials and new techniques of construction which would demand fewer resources. Construction creates pressure on resources in many ways. For example, a lower life of structures requires constant construction or reconstruction of existing structures, greater requirement of building materials due to their low strength to weight ratio, inability to optimally use certain materials and their properties relevant for structure and their loading condition. I am happy to say that the new materials and construction techniques are closing these gaps.
Reducing cement content and replacing it with fly ash or GGBFS reduces carbon dioxide emission and water consumption. What is your view of this practice?
Yes, replacing more cement with either fly ash or GGBFS are common strategies to reduce the carbon footprint. Reduction of cement is now also being done through particle packing at the microscopic level. The reason why we have finer cement today as compared to cement of almost 20 years ago, is because fine cement is being used more and more. The strength we achieve at 28 days with a low cost of grinding, is not more than the strength that we get for higher cost of grinding with significant reduced cement content. This is due to the rising cost of transportation w.r.t. the cost of grinding the clinker at the mills.
Reduction in cement content is also possible with ultrafine mineral additives to a significant level from M25 grade onwards. These materials have proven that they can reduce the cost of concrete not just for high grades but also for normal high volume grades. This is essentially due to the proximity of the manufacturing units (which save transportation costs) compared to the imported microfine materials that we got earlier.
We are seeing more and more new ultrafine materials which improve the hydration of cement particles and also the strength properties due to their surface characteristics. In other words, optimum fineness and distribution of particle sizes through supplementary cementitious materials is the way forward towards sustainability.
Concrete Construction September - October 2022
