Risk of environmental contamination arising from concrete structures, Part I: CO2 emission

Abstract

The present study concerns the CO2 emission in the process of cement manufacture. Information on raw materials, energy source and oxide composition was achieved from Korean major six manufacturers. As a result, it was found that the energy efficiency for kilning and control for a loss of CaO in cement manufacture are key factors to emission of CO2. The variation in the amount of coal in the process of kilning accounted for about 30 kg for one tonne of cement, as being equivalent to 70 kg CO2/tonne-cem. Simultaneously, the loss of CaO in refinement of raw materials is crucial in reducing the CO2 emission. The loss of CaO in the cement production was in the range of 9-24 kg for one tonne of cement, which may impose unnecessary energy of coal in kilning and a further decomposition of CaCO3 to CaO and CO2. Substantially, it can be said that energy control for high efficiency of coal in the kilning process and control for a loss of CaO may reduce several hundreds kg CO2/tonne-cem, compared to 729-911 kg CO2/tonne-cem in the cement production. Alternatively, the use of pozzolanic material for Portland cement can reduce the CO2 emission. 30% PFA and 60% GGBS in a concrete mix reduced CO2 emitted for a given mix about 28.9 and 49.6% respectively, compared to Portland cement.