Response surface optimization of CO2-mixing mineralization concrete: Balancing mechanical properties and carbon sequestration

This study optimized the mix proportions of low-carbon concrete with CO2-mixing mineralization using Response Surface Methodology (RSM) and Box-Behnken Design (BBD). Steel slag (SS) content, fly ash (FA) content, and CO2 dosage were treated as independent variables, with slump (S.P.), 3-day compressive strength (3d-C.S.), 28-day compressive strength (28d-C.S.), and CO2 fixation rate (C.F.) as response variables. Results showed that FA content positively affected S.P., while CO2 dosage negatively impacted it. SS content positively influenced 28d-C.S., while FA, SS, and CO2 all negatively affected 3d-C.S., with FA having the strongest impact. C.F. was most responsive to CO2 dosage, increasing by 39.2% with an increase in CO2 from 0.4 wt% to 1.2 wt%. This study highlights the limited role of FA in improving concrete performance under CO2-mixing conditions and provides new insights into the mechanisms of CO2-mixing mineralization concrete.