Embodied CO₂-based optimal design of concrete with fly ash considering stress and carbonation

This paper proposes a method for the optimal design of concrete by incorporating fly ash. First, an optimal design with the aim of reducing the CO2 emissions was developed. Various constraints, such as the strength, slump, and carbonation with stress, were considered. Second, optimal mixtures were obtained using a genetic algorithm considering the aim functions and various constraints. The results obtained from the analysis demonstrate that, for low-strength concrete, carbonation dominates the mixtures, whereas for high-strength concrete, strength dominates the mixtures. Additionally, the stress types and levels affect the optimal mixtures. A rich mixture is crucial for structural elements with high-level stresses. Furthermore, compared with that of compressive stress, the effect of tensile stress on the mixtures is evident. Finally, optimal designs considering the material costs and embodied energy were performed. These optimal mixtures with low costs or low embodied energy are similar to those with low CO2 emissions.