Flexural optimization of slag-based geopolymer concrete beams modified with corn cob ash

The present study investigates the flexural strength of Geopolymer Concrete (GPC) beams produced by Ground Granulated Blast Furnace Slag (GGBFS) and Corn Cob Ash (CCA). In the Design Of Experiment (DOE), Box-Behnken Design (BBD) of Response Surface Methodology (RSM) was used to optimize the strength. GGBFS was replaced at 0, 20, and 40 wt.% of CCA. The mixes were activated with 14 molar concentration (14 M) of both sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions. The mix design properties such as alkaline liquid-to-binder ratio, binder-to-aggregate ratio, binder ratio, and curing time were statistically employed as continuous (independent) variables to optimize the response factor ( flexural strength). Compared to the control sample (Portland cement concrete), GPC exhibited higher compressive and flexural strengths at up to 40 wt.% of CCA replacement. The models predicted the response of flexural strength with the variability of less than 5%. Moreover, the correlation between the experimental and optimized flexural strengths yielded high precision with 99.6% /R2". Therefore, the response models in this study would be advantageous in optimization of mix design proportions to obtain the target flexural strength of GPC beams produced by GGBFS and CCA.