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

Document Type : Article


1 Department of Civil Engineering, Covenant University, PMB 1023, Km 10, Idiroko Road, Ota, Nigeria

2 Department of Civil and Environmental Engineering, Delta State University, Oleh Campus, Abraka, Delta State, Nigeria


This study investigated the flexural strength of geopolymer concrete (GPC) beams produced with ground granulated blast furnace slag (GGBFS) and corn cob ash (CCA). The design of experiment (DOE), Box-Behnken design (BBD) of the 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 applied as continuous (independent) variables to optimize the response factor (flexural strength). Compared with 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 less than 5% variability. Besides, the correlation between the experimental and the optimized flexural strength yielded a high precision with 99.6% “R2”. Therefore, this study's response models would be advantageous in the optimization of mix design proportions for obtaining target flexural strength of GPC beams produced with GGBFS and CCA.


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