Cement, Energy and Environment

approach, which addresses the central issue related to need of making high temperature and lime intensive alite phase in cement for achieving strength, is therefore necessary for maximizing synergy between sustainability and profitability. Maximizing synergy between sustainability and profitability by producing less energy intensive alternative cements: One of the non-conventional approaches which hold a potential of fulfilling objective of transforming ourselves into eco-friendly cement producer is to extend our product portfolio with low energy intensive cements like Reactive Belite Cement (RBC), Mineralized Clinker Cement (MCC), Calcium Sulfa-aluminate Cement (CSC) and Portland Limestone Cement (PLC) over a period of time. Amongst these products first three types essentially alter the mineralogical characteristics of the clinker whereby the dependence of functional properties of the cement on high temperature stabilizing Alite phase (C 3 S) is minimized by either synthesizing alternative low temperature strength giving mineral phases or making other phases in regular clinker more reactive, thereby circumventing fundamental need of high temperature processing. In doing so, the so called detrimental minor elements in the current context (alkali, sulfur, magnesia, etc.) are utilized to our advantage in stabilizing more reactive belite or sulfoaluminate phases requiring much less limestone and correspondingly lower heat/energy. In other words, the concerns of the manufacturing units, namely increased impurities and low lime content, can in fact be utilized advantageously to effectively address sustainability issues. The other cement namely PLC on the other hand concentrate on reducing clinker content in the cement similar to PPC but in a much cost effective manner. However, easier said than done, creating this paradigm shift in manufacturing practice requires bold decisions to account for factors like • Willingness to accept more radical departure from traditional cement phase compositions and manufacturing practice • Change in mindset of targeting higher early strengths than that required for practical purposes and durability aspects • Generation of first hand reliable concrete durability data for cements made in bulk using such non-traditional routes in Indian context • Dedicated research and developmental effort to accommodate and integrate technological requirements of such non-conventional cements into existing plants • Modification of existing standards and specifications which can accommodate these new products without affecting customer aspirations In fact some of these products (for example CSC and PLC) are being actively pursued in different countries in Asia (excluding India) as well as in Europe by focusing and educating the customers about the needs of construction industries for 'structural durability' rather than only 'strength'. Thus apart from energy and resource conservation, other striking advantage of these cements is their enhanced durability in concrete applications as compared to regular concrete. Understandably the onus of exploring newer eco-friendly cements along with fulfilling need of ever increasing demand for cement and concrete lies on market leaders especially in developing countries as opposed to players in developed countries which are not yet as hard pressed for resource crunch due to near saturation condition in cement consumption and relative abundance of high grade raw materials. Being a market leader in India our cement business can afford to experiment with such products in a calibrated manner for leading the way towards effective sustainability. Following sections elaborate salient features of such non-conventional cemenUclinkers further in the light of their technical specs, cost– benefit implications, etc. Reactive Belite cement, Calcium Sulfa– aluminate Cement and Mineralized Clinker Cement: Industrially Alite in Ordinary Portland clinkers is formed by effecting reaction between belite and free lime at temperatures exceeding 1400 deg C followed by rapid quenching in coolers. High-Belite cements are those in which there is a reversal in the preponderance of Alite by Belite without sacrifice of early age strength in mortar and concrete. Since this implies higher levels of early reactivity in Belite, such cements are also known 10