What is the environmental impact of using PFA in concrete?
PFA is pozzolanic and can be used as a partial cementitious material. As such it reduces the quantity of Portland Cement required. Due to the chemistry of Portland cement and the temperatures required to produce cement, for every tonne of PC made produces ~900kg of CO2. By replacing 30% of the total cement content with PFA the overall environmental impact has been shown to be reduced by at least 17% for the same 28 day strength. With some types of concretes for certain exposure classes (See BS EN206-1 and BS 8500) reductions in emissions of >50% are possible. With High Volume Fly Ash (HVFA) concrete, which contains between 55 and 70% PFA, or when the specified strength is at 56 days or more, even greater reductions in the environmental impact are achievable. When PFA is incorporated in structural concrete there is a reduction in leaching potential. The pozzolanic reaction reduces the permeability effectively preventing any significant leaching from either the PFA, the Portland cement o
