Er. Kaushal Kishore ,
Materials Engineer, Roorkee
Portland cement, is made by a calcareous material, such as limestone or chalk, and from alumina and silica found as clay or shale. The process of manufacture of cement consists essentially of grinding the raw materials, mixing them intimately in certain proportions and burning in a large rotary kilin at a temperature of up to about 14500C. When the material sinters and partially fuses into balls known as clinker, the clinker is cooled and ground to a fine powder, with some gypsum added, and the resulting product is the commercial portland cement so widely used through out the world. The manufacturing of this cement release in the atmosphere 0.8 tonnes of CO2 in the production of one tonne of cement. When water is mixed with cement and aggregates in the production of concrete for use in the construction, each tonne of cement can absorb up to 0.4 tonnes of CO2 , but that still leaves an overall carbon footprint per tonne of 0.4 tonnes. In the year 2009 about 2000 million tonnes of CO2 was emitted in the atmosphere in the production of cement.
The above problems have been overcome from researches by Nikolas Vlasopoulos Chief Scientist and his colleagues at Imperial College, London, and they have set up a company of Novacem’s cement which is making cement from magnesium silicate that absorb more CO2 as it hardens. Valaspoulos responded that magnesium slicates are abundant world wide with 10,000 billion tonnes available. He is confident that material will be strong enough for use in buildings but acknowledge that getting licence to use it will take several years of testing.