Mixture Optimization of Sustainable Concrete with Silica Fume Considering CO2 Emissions and Cost

Abstract

This research presents a framework for the mixture design of sustainable SF-modified concrete. The design strength at 28 days was scaled to different values (e.g., 30, 40, 50, and 60 MPa). CO2 emissions and cost were chosen as the design variables to optimize. Strength, slump, and carbonation durability with global warming were applied as constraints of optimal design. The analysis revealed that, for low-CO2 concrete, when the design strength was 30 or 40 MPa, to fulfill the requirement of carbonation, the actual concrete strength ought to be 45.39 MPa, which was much greater than the design strength. Carbonation did not affect the mixtures scaled to a high design strength (50 and 60 MPa). The SF/binder ratio was maximum for low-CO2 concrete. Furthermore, for low-total-cost concrete, when the design strength was 30 MPa, the actual strength was 31.28 MPa after considering carbonation. Moreover, when considering global warming, the actual strength should be 33.44 MPa. The SF/binder ratio was minimum for low-cost concrete. Lastly, for low-material-cost concrete, the design was equivalent to the low-total-cost concrete, along with much lower CO2 emissions. In summary, the suggested technique is valuable for the design of sustainable SF-modified concrete with low CO2 and low cost.