Structural concrete and sustainability

Abstract

During the manufacture of Portland-type cements, significant emissions of carbon dioxide occur, some of which comes from the burning of fuel in the kiln, and the balance from the chemical dissociation of limestone (CaCO3). In South Africa the typical specific CO2 per ton of cementitious binder is about 765 kg. However, the effect of this is significantly diluted by the addition of aggregates (around 80% of the mass of a cubic meter of concrete) and cement extenders, of which many are industrial by-products (up to 50% of the mass of binder which typically is about 15% of the mass of a cubic metre of concrete. In order to optimise the embedded energy of a particular concrete structure it is necessary to make decisions on the selection of the concrete materials to be used on a particular project and this chapter gives guidance to the design and construction teams on how to make these decisions. The designer should also give consideration to passive design factors, as the most significant proportion of the energy consumed in a structure during its lifetime is taken up during the operation of the building through the provision of lighting and climate control.