Cement, Energy and Environment

Abstract Production of blended cements has a long history in India. Growth in production of PSC has been in conformity with the availability of granulated blast furnace slag and market demands, while that of PPC has been phenomenal with utilization of over 50 million tonnes of fly ash. There is a notable reduction in the clinker factor and the factor can be brought down further with the introduction of composite cement. The low-carbon transition roadmap for the industry has made a prognosis that in order to meet the target of CO emissions intensity in 2 2050 the trajectory of production and application of blended cements has be more innovative and eco-friendly. The present article is an attempt to revisit the expanding field of blended cements in India from the perspectives of durability, sustainability and climate change Introduction Globally and nationally speaking, the cement industry has proven itself to be an environmentally and socially responsible manufacturing enterprise. Technologically the manufacturing units in most cases are not only efficient but also compliant to health, safety and environmental standards. It has made significant advances in addressing the issues of resource conservation and greenhouse gas (GHG) emissions. The industry has turned out to be the most promising platform for solid waste management in the world. Amongst the various levers used by the industry to achieve its environmental objectives, a prominent one is to reduce the clinker factor in production of cement so that the specific emissions of CO can be 2 reduced. Generally speaking, 0.96 t of CO is emitted from 2 the production of 1 t of clinker as it exits the kiln. The emissions are reduced to 0.92 t of CO per tonne of cement, 2 when the clinker is interground with gypsum to produce Ordinary Portland Cement (OPC). Furthermore, when a blended or composite cement is produced, the emissions can be reduced to 0.65 to 0.80 t of CO per tonne of cement, 2 depending on the types and quantities of supplementary cementitious materials (SCM) added to the cement. The impact of SCMs used in manufacturing blended cement is, therefore, significant in this respect. The Indian cement industry, the second largest in the world, took up the mission of maximizing the production of blended cements decades back, initially to meet the country's ever-increasing demand for cement, but in the last decade, more for reducing the CO emissions. The 2 present paper is an attempt to look into the status and trends of blended cement production in India in the above backdrop. History of Blended Cements Production in India It is generally believed that the basic concept of making blended cements owes its origin to the ancient practices of using natural siliceous materials in lime mortar and concrete. Based on the relicts of Mohenjo-Daro and Harappa, it is acknowledged that that the use of lime-pozzolana mixture as a hydraulic binder was adopted in our sub-continent even in the pre-historic times. Anjan K Chatterjee Former Wholetime Director, ACC Ltd, Mumbai & Chairman, Conmat Tecnologies, Kolkata BLENDED CEMENTS AND SUSTAINABILITY: AN INDIAN PERSPECTIVE 16