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Supplementary Cementing Materials

SCMs Help Reduce Emissions

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Increasing the use of supplementary cementing materials (SCMs) is a proven method of addressing climate change and clean air. 

SCMs are materials that can be interground with cement clinker to produce blended cement, or can be directly added to a concrete mix as a complementary agent.  SCMs are waste products from other industries that would otherwise require disposal. In Canada, commonly used SCMs include fly ash, blast furnace slag and silica fume. 

Approximately 60% of greenhouse gas emissions associated with cement production are irreducible process emissions that result from heating raw materials to form cement clinker.  For each tonne of supplementary cementing materials used in place of pure Portland cement, approximately one tonne of greenhouse gas emissions is avoided.  This practice also has the added environmental advantages of avoiding air pollutant emissions, reducing energy consumption, making use of materials otherwise destined for landfill, and increasing production capacity without installing new kilns.

Since 2004, the Canadian cement industry has improved its clinker/cement factor, the proportion of pure portland cement used in making cement, from 86% to 83%.  Based on 2006 data, the global average clinker to cement ratio was 0.78. In 2008, the Canadian average clinker to cement ratio was 0.83.

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Currently, the use of blended cements of SCMs to produce concrete typically replaces 20% of the energy-intensive clinker that would otherwise be required to produce a cubic metre of concrete. In 2008, this resulted in a 1.4 million tonne reduction in CO2 emissions in Canada.