Carbon emissions assessment of concrete and quantitative calculation of CO2 reduction benefits of SCMs: A case study of C30-C80 ready-mixed concrete in China

This study elucidates the changes in carbon footprint variations in concrete production processes and component contributions due to the use of supplementary cementitious materials (SCMs) and changes in raw material transport distances through the establishment of a large-scale concrete mix proportion database and life-cycle assessment (LCA). The average carbon emissions for C30-C80 concrete were calculated to range from 262.21 to 401.78 kgCO 2e /m 3 , with data showing significant dispersion due to uncertainties in raw materials and experimental conditions. The incorporation of SCMs leads to substantial and unstable changes in cement content, but still generally reduces carbon emissions of concrete by 5 %-30 % at the same strength level, and increased transport distances have little effect on this reduction rate, which diminishes to zero only when distance exceeds 4166 km. In contrast, transporting aggregates over long distances (from 100 km to 500 km) increases carbon emissions by more than 10 % due to huge mass. Manufactured sand (MS) reduces transport emissions when replacing 50 % and 100 % of natural fine aggregates (NFA) but is scarcely beneficial to total CO 2e emission due to its higher production energy consumption and negative impact on concrete strength. This study highlights the low-carbon potential of SCMs and underscores that reducing production energy consumption and enhancing material performance are crucial for maximizing the comprehensive low-carbon benefits of MS.