Cement, Energy and Environment

th Fig.1. Transformation of products mix in the last decade of the 20 century. Table 1. Cement production trends in the previous two decades Year Total cement, Mt PPC % PSC % Total blended cements % OPC % Others % 2005 + 137 50.09 7.94 58,03 41,52 0.45 2009 + 203 62.50 7.61 70.11 29,49 0.40 2017* 280 65.00 7.00 72.00 27.00 1.00 Note: + Data from CMA; * Data from WBCSD (LCTR review 2018) From the available data it appears that in 2017 the Clinker Factor (CF) for PPC and PSC were 0.65 and 0.40 respectively, while the CF for OPC was close to 0.94. Taking into account other cements produced during the year, the weighted average CF works out to be 0.71. The entire quantity of GGBS available in the country continued to be used up in making PSC but since the amount of granulated slag is limited to 10-11 Mt per year or less, the PSC production has remained flat below 8% during the last few years, notwithstanding the growth in cement production. The major thrust has been on producing PPC with fly ash, the specific consumption of which in the majority of the plants has been raised to about 34%. R ecent Modification in the PPC & PSC Standards A very important development in the standard specifications of PSC and PPC that has taken place in 2018 is the introduction of grading of these cements based on their 28-day mortar strength at par with OPC. The issue was under consideration of the Bureau of Indian Standards since February 1995 but various technical and legal hurdles came in the way of implementing the grading of the two major blended cements in India for over two decades. To start with, the issue of grading the blended cements originated out of a techno-commercial compulsion in the cement market. It is known that the criteria by which cement produced by one manufacturer can be distinguished from the product of another are extremely limited. Compressive strength has always been the primary, if not the singular, distinguishing parameter for cements. In the predominantly retail market of bagged cement in India, the competitive marketing has mostly relied on high 1-day non-standard mortar strength property, and rapid strength gain in early age, both of which are normally not inherent in the blended cements. Hence, some of the producers and users of blended cements were strongly in favor of grading the blended cements in late 1990s. Further, the European standard (EN 197- 1:2000), which defined the quality of all types of cements produced in all member countries in a matrix of SCMs and strength, was the reference point to justify grading of blended cements in India, although the comparison of India as a single country with the European Union as a conglomerate of countries has been unequal. What is important to note to-day that the eventual delay of almost 25 years in implementing the 18