New cementless concrete for construction
Concrete is the most popular building material due to its versatility. Cement is an essential ingredient of concrete. But each tonne of cement releases around 0.7 tonnes of carbon dioxide into the atmosphere during its manufacture. There is a need to reduce carbon emissions by various means. There are new methods of minimising these emissions by reducing or eliminating the use of cement.
In the case of blended cement, there is partial replacement of cement by different cementitious materials such as fly ash, granulated slag, etc. In case of high-volume fly ash concrete, the replacement of cement exceeds 50%.
There are relatively new materials in which traditional cement can be completely avoided. FaL-G and Geopolymer are two of them. They can be used in making paste, mortar bricks and concrete.
* FaL-G is made up of fly ash, lime and gypsum which are the by-products of thermal power plant, paper and fertilizer industry. This needs traditional curing to gain strength. This material is extensively used in Bhadrachalam and surrounding areas for various projects. It is best suited for low cost housing.
* Geopolymer is made out of fly ash, granulated slag and chemicals like sodium hydroxide/silicate. Geopolymer masonry blocks and concrete do not need traditional curing and certainly no thermal energy is required to gain strength. Also, they are highly resistant to acids, sulphates, elevated temperature and other aggressive exposure. They are found in many industrial applications due to fast production, and are used in Australia. In India, geopolymer remained as a laboratory material due to various reasons. There is a scope for developing this material for various applications in the construction industry.