Corn cob incorporated lightweight concrete: Experimental evaluation and mechanical strength optimization using response surface methodology

Corn cob, an abundant agricultural waste, was investigated as a partial replacement for conventional coarse aggregate in the production of lightweight concrete. This study evaluated the effects of corn cob aggregate replacement levels (5%, 7.5%, and 10% by volume) and water-cement ratios (0.50–0.60) on concrete performance. Experimental investigations included slump, oven-dry density, compressive strength (CS), split tensile strength (STS), flexural strength (FS), water absorption, and sorptivity tests, while thermal conductivity was estimated using a density-based empirical model. Response surface methodology (RSM) was employed to develop predictive models and optimize mechanical performance, and a cradle-to-gate life cycle assessment estimated embodied CO₂ emissions. The mixtures exhibited oven-dry densities of 1570–1793 kg/m³ and compressive strengths of 18.3 ± 0.71–22.6 ± 0.98 MPa (mean ± SD, n = 3). Increasing corn cob content reduced density and estimated thermal conductivity but increased water absorption. The RSM models demonstrated strong predictive performance for CS, STS, and FS, with validation errors below 4%. The life-cycle assessment indicated approximately 6% lower embodied CO₂ emissions than those of conventional concrete. These findings demonstrate the potential of corn cob aggregate for producing lightweight concrete with promising mechanical performance and modest environmental benefits.