Title: Response Surface Analysis and modelling of Water-Cement Ratio and Curing Age Effects on the Compressive Strength of Selected Nigerian Cement Brands
Authors: Damini Righteous Gilbert and Arogo, Eyaramuonan Charles
Volume: 10
Issue: 2
Pages: 44-55
Publication Date: 2026/02/28
Abstract:
The compressive strength of concrete is strongly influenced by water-cement (w/c) ratio and curing age, yet the combined effects of these factors for Nigerian cement brands remain underexplored. This study investigates and models the influence of w/c ratio and curing age on the compressive strength of concrete produced using BUA, Dangote, and Elephant cements. Three representative mix proportions 1:1:1 (rich), 1:1.5:3 (standard structural), and 1:2.5:5.5 (lean) were prepared with w/c ratios ranging from 0.25 to 0.60. Workability was assessed using slump tests, while compressive strength was measured at 7, 14, and 28 days. Response Surface Methodology (RSM) was employed to develop quadratic predictive models, and one-way and two-way ANOVA were conducted to evaluate factor significance and interactions. Results indicate that both w/c ratio and curing age significantly affect compressive strength for all brands (p < 0.0001). One-way ANOVA shows that variations in strength are predominantly controlled by w/c ratio, with high F-values and minimal residual variance. Two-way ANOVA confirms the main effects' significance, while interaction terms are generally non-significant. Optimal w/c ratios were identified as 0.35 for the rich mix, 0.50 for the standard mix, and 0.40 for the lean mix, with strength reductions of up to 44.7% beyond these levels. Among the brands, BUA exhibited the highest compressive strength, followed by Dangote and Elephant. The quadratic RSM models demonstrated strong predictive capability, providing a practical framework for brand-specific optimization of concrete mix design under Nigerian construction conditions.