Optimization of Design Parameters of Slag-Corncob Ash-Based Geopolymer Concrete by the Central Composite Design of the Response Surface Methodology

This study applied the central composite design of the response surface to optimize the mix parameters in the production of ground granulated blast furnace slag (GGBFS)-based geopolymer concrete (GPC) incorporated with corncob ash (CCA) using grade 30 (M 30) and grade 40 (M 40) concrete as design proportions. The influence factors such as binders (B), curing time (t), and concentration of alkaline activating solution (M), and the response (compressive strength) were optimized in accordance with the 2(2)factorial design of the full central composite, the factors were analyzed and compared with the experimental (input) values. The optimization values showed the maximized compressive strengths as 50.70 and 62.92 MPa with the composite desirability (D) of 1.0000 and 1.0000 at the minimizedB,t, andMas 390 and 500 kg/m(3), 74 and 83 days, and 14 and 14 M for M 30 and M 40, respectively, compared with the experimental values, having the maximum compressive strength of 48.23 and 62.09 MPa for both M 30 and M 40 at 90 days of curing with 14 M. Hence, this study statistically and optimally offered a better fitting of the designed parameters and the experimental results showed a good conformity with the optimized results.