View GeoFile 2008-9 (PDF, 826 KB)
Portland cement production is an energy intensive process involving the use of fossil fuels. Cement plants are considered to be significant stationary sources of greenhouse gas emissions. The cement industry is succeeding in the reduction of “Fuel-related” CO2 emissions per tonne of cement produced by increasing the efficiency of cement making equipment, increasing the use of biofuels and alternative fuels, and by reducing the use of Portland Cement through the increased use of blended cements (without sacrificing quality).
This poster introduces the cement-making process, describes how CO2 is generated during Portland cement production, explains the blended cement concept, and demonstrates how the increased use of blended cement is resulting in substantial reductions of CO2 emissions.
Blended cement has chemical and physical properties similar to those of traditional Portland cement (the main cementitious material used to make concrete); however, it commonly consists of 10-30% (in some cases up to 50%) additives that do not require, or require only low temperature calcining. These additives are supplementary cementitious materials (SCMs) or natural pozzolans. They include fly ash, silica fumes, volcanic ash, scoria, pumice, silica sinter, metakaolin, slags, zeolites, diatomaceous earth, rice husk ash, calcined shale, and a number of other materials. As a result, the production of blended cement requires the combustion of a smaller quantity of fossil fuels than Portland cement. The reduction in the use of Portland cement also lowers the level of raw material - related emissions emitted by the calcination of limestone.
The most common secondary cementitious material in British Columbia (BC) is imported fly ash. BC has a variety of locally available secondary cementitious resources. Most of these resources are undeveloped and a lot of them remain untested.
In BC, the substitution of imported fly ash by domestically available pozollans would not be without challenges, but if economically and technically viable, it could benefit the mining industry, help the environment by reducing CO2 emissions and create employment.
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