Search

The issues of environmental impacts of concrete have become important since many major infrastructure owners are now requiring environmentally sustainable design (ESD). The carbon dioxide (CO2) emissions are often used as a rating tool to compare the environmental impact of different construction materials in ESD. Currently, the designers are forced to make estimates of CO2 emissions for concrete in ESD based on conjecture rather than data. The aim of this study was to provide hard data collected from a number of quarries and concrete manufacturing plants so that accurate estimates can be made for concretes in ESD This chapter presents the results of a research project aimed to quantify the CO2 emissions associated with the manufacture and placement of concrete. The life cycle inventory data was collected from two coarse aggregates quarries, one fine aggregates quarry, six concrete-batching plants and several other sources. The results are presented in terms of equivalent CO2 emissions. The potential of fly ash and ground granulated blast furnace slag (GGBFS) to reduce the emissions due to concrete was investigated. A case study of a building is also presented. Portland cement was found to be the primary source of CO2 emissions generated by typical commercially produced concrete mixes, being responsible for 74–81% of total CO2 emissions. The next major source of CO2 emissions in concrete was found to be coarse aggregates, being responsible for 13–20% of total CO2 emissions. The majority contribution of CO2 emissions in coarse aggregates production was found to come from electricity, typically about 80%. Blasting, excavation, hauling, and transport comprise less than 25%. While the explosives had very high emission factors per unit mass, they contribute very small amounts (