Blended Cements - the Carbon Fighter
Blended Cements - the Carbon Fighter

Blended Cements - the Carbon Fighter

Blended cements are cements produced by inter-grinding clinker along with mineral components (MiC) such as fly-ash or slag, both of which are industrial by-products or industrial waste. This may sound quite a simple proposition on the face of it, but this simplistic statement defining the term blended cement hides a lot of history behind its facile façade. The journey of blended cements in India has been tortuous, and topsy-turvy, and the story makes for fascinating reading. Regulatory interventions, commercial availability and opportunity pricing of MiC, idiosyncrasies of the market, indifference of the influencers, conflicting views within the industry itself, and many other such interesting factors contributed to make this journey very complex and colourful.

This eventful journey is seen very aptly, in the changes in the product mix of India Cement Industry. The product mix is reflected in the percentage of ordinary cement (Ordinary Portland Cement or OPC, in short) vs percentage of blended cement (PSC - Portland Slag Cement and PPC - Portland Pozzolona Cement). In 1978/79, the product mix was almost 50:50, between OPC and blended cement (most of which, in those days, would have been slag cement. In 1983, this mix became adverse for blended cement, because OPC percentage rose to a high of 76 per cent, while blended cement percentage dropped to a lowly 24 per cent.

We have to keep in mind that during this time, the industry was being gradually decontrolled by the government, and we must juxtapose the impact of this regulatory disruption on the product mix changes. While so far, blended cement was dominated by slag cement (PSC), and rightly so, as India was setting up more and more integrated steel plants, and slag was being made available int different parts of the country, particularly in the eastern India, action now started shifting towards fly ash-based PPC cement around this time, as more and more coal-based (that too, based on typically high ash content coal of India) thermal power plants started coming on stream, and were producing hazardous fly ash in millions of tonnes. So it was, that around the year 1987, the product mix once again was balanced, at about 50:50, but this time pushed more due to the advent of PPC. And, the march of PPC went on unabated, till today, when the product mix battle is being won decisively by blended cement, and the proportion is now around 70 per cent blended (PPC + PSC) and only about 30 per cent of PPC. There is no reason why this cannot move up to even 85:15 ratio.

That is good news for the climate change battle. We know that CO2 emission is a function of fuel burnt and/or energy consumed. Consider that, on an average, a ton of OPC needs 90 KWh energy, while PPC needs 85 and PSC needs even lesser at 80 KWh/T. In fact, driven by India's sterling performance in introducing blended cement into the market and success of the industry in gaining market acceptance for these blended products, we have one of the lowest specific CO2 emissions per tonne of cement produced, in the world.

Last year, the Bureau of Indian Standards (BIS, the regulatory body that controls cement grades and specifications in India) has permitted introduction of composite cement and have specified the quality criteria etc., for this product. Composite cement is a blend of blends, in the sense that the manufacturers can blend both fly ash and slag into one product, one bag, which will be called composite cement. There may be a few manufacturing challenges which may require some new investments, but in the end this will help to further increase the component of blended cement in the total product mix of Indian cement industry.

Sumit Banerjee Chairman, Editorial Advisory Board

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