Abstract:To realize the multi-objective performance of concrete proportion design, this study employed single-factor experiments to establish the optimal ranges for slag content, fly ash content, and water/binder ratio in C40 ready-mixed concrete. Using the response surface methodology, quadratic regression models were developed to systematically analyze how these three factors influence concrete slump and compressive strength. The NSGA-II algorithm was further applied in combination with TOPSIS comprehensive evaluation method to achieve multi-objective optimization of the mix proportion. The results demonstrated that the regression model established by response surface method has high accuracy and reliability, with correlation coefficients R2 of 0.9447 and 0.9604. The influence of fly ash content on slump was significant, while the influence of water/binder ratio on compressive strength was significant. The optimal mix proportion was obtained after optimization: slag content of 8.66%, fly ash content of 25%, and water/binder ratio of 0.34. Experimental verification showed that the relative error between predicted and measured values was less than 5%. This study provides a theoretical basis and reference for the optimal design of concrete proportion.