Sustainable design of low-CO2 hybrid concrete incorporating calcined clay and limestone powder

Abstract

Calcined clay and limestone powder are increasingly utilized to create sustainable concrete. This paper proposes a low-carbon design approach that involves the addition of calcined clay and limestone powder. The goal of optimized design is to minimize the carbon emissions, and the constraints of optimized design include strength and carbonation durability. Four different optimization design options were considered. Option 1 does not consider carbonation durability, only strength. The results of the optimized design show that the carbonation durability cannot be satisfactory for low-strength (30 MPa) and medium-strength (40 MPa) concrete. Option 2 considers strength and carbonation durability. The carbonation durability life is 50 years, and the CO2 concentration is 0.04 %. The results show that there is a cutoff point for strength (42.72 MPa). Below this cutoff point, the carbonation durability dominates the optimized design, and above this cutoff point, the strength dominates the optimized design. Option 3 also considers strength and carbonation durability. Compared with option 2, the CO2 concentration increases to 0.05 %. The results show that the strength cutoff also increased from 42.72 MPa to 46.45 MPa. Option 4 considers harsh carbonation conditions. The carbonation durability life is 100 years, and the CO2 concentration is 0.05 %. The results show that the actual strength (59.64 MPa) is the same for different design strength levels (30, 40, and 50 MPa). Considering the results of the optimized design, we discovered that as the strength increased, the CO2 emissions increased, and the water/binder ratio decreased. This finding illustrates the effectiveness of this method.