Conventional concrete is made up of cement, fine aggregate, coarse aggregate, water and chemical admixture, if necessary, in specified proportion. Concrete is widely used as a construction material because of the good strength of Reinforced cement concrete (RCC). The cement which acts as a binding agent in a concrete mix is a pollutant. Almost 5 to 6 percent of carbon dioxide (CO₂) gases are attributed to cement industry alone and this is one of the biggest contributors to the pollution and carbon footprint. In addition to this, the consumption of energy in concrete industry further led to carbon emissions.

India is the second largest manufacturer of cement in the world. Carbon dioxide released by cement industry along with other human activities, mostly because of the fossil fuels that people are burning for energy. Because of the rapid increase in CO₂ emission in 21st century, the planet is suffering from global warming, frequent floods, draughts, fires and numerous other problems. The planet is going through an existential crisis, citing an urgent need for scientific and innovative steps to secure humanity’s future.

India at UNFCCC CoP-26 announced its commitment to achieve net zero carbon emission by 2070. India particularly needs to focus on a smoother renewable energy transition, greater adoption of electric vehicles and greater participation from the government and from the individual.

If we are able to cut the CO₂ released by the cement industry, we would achieve the target of net zero carbon emission earlier than 2070.

The carbon emission from cement industry can be reduced by two approaches:

1. Replace concrete as a construction material by other sustainable materials
2. Replace the cement (wholly or partially) as a binding material in concrete

Complete replacement of concrete in the construction industry would seem hard to achieve. It is hard to imagine a lighter weight, equally strong, abundant and cheap material for high rise construction and infrastructure projects. For now, it seems impossible to completely replace concrete by other sustainable material. Rather than evade the use of concrete, we should think about composite construction techniques by adopting new construction materials which will lead to minimizing concrete usage.

The continuous research on the effective materials to replace cement would play a big role in the construction industry. For now, we will only be able to partially replace cement with supplementary cementitious materials. This is largely due to the inherent properties of the constituent materials of conventional concrete. we can reduce the cement usage by replacing with some percentage of fly ash, silica fume, limestone ash, rice husk ash and sawdust ash but we cannot avoid the cement fully not only that even research have been done with this ash by adding gypsum and lime but it is not up to the mark of cement strength.

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