The carbon footprint of reinforced concrete

As legislation forces significant reductions in the operational carbon dioxide emissions of the built environment, increasing attention is focused on the embodied carbon of structural materials. As the most prevalent structural material, the embodied carbon of concrete is of paramount interest. Previous direct or indirect analyses of embodied carbon in concrete have treated it either as an elemental material with a value of single embodied carbon, or calculated embodied carbon for a limited range of reinforced concrete mix designs, or returned only values for plain concrete. In this paper, the results are presented from a preliminary study into the embodied carbon of reinforced concrete as a function of: concrete strength grade; steel strength; mix design; cement replacement; and structural form. Findings are expressed both in terms of EC_raw (kgCO₂/kg reinforced concrete) and EC_f (kgCO₂ per unit of structural performance). They suggest that there is a wide range of EC_raw (0·06−0·47) and that EC_f is minimised by using C50 concrete. Savings in EC_f achieved by adjusting mix design parameters (20–35%) generally exceed those achieved by replacing cement with pulverised fuel ash (10–25%). C50 beams of all mix designs have lower EC_f than comparable timber composite or steel beams.