TAGUCHI OPTIMIZATION OF FLEXURAL STRENGTH OF BINARY SUPERPLASTICIZED CONCRETE CONTAINING CALCINED MOUND SOIL AS PARTIAL CEMENT REPLACEMENT

Abstract

Increasing demand for sustainable materials for construction has necessitated the exploration of supplementary cementitious materials that can reduce Portland cement consumption without compromising structural performance. This study evaluates flexural strength optimization of grade 40 binary superplasticized concrete incorporating calcined mound soil to partially replace ordinary Portland cement using Taguchi optimization technique. Four control factors comprising cement content (400–450 kg/m³), water–cement ratio (0.31–0.35), superplasticizer dosage (0.6–1.0%), and mound soil replacement (10–20%) were investigated using the Taguchi L₉ orthogonal array. Nine experimental mixtures together with a control mix were produced and tested for 28-day flexural strength. Experimental results indicated flexural strengths ranging from 3.90 to 5.10 N/mm², with the highest value obtained at 450 kg/m³ cement content, 0.33 water–cement ratio, 0.8% superplasticizer dosage, and 15% mound soil replacement. The Taguchi "larger-is-better" signal-to-noise (S/N) ratio was employed to evaluate the optimum combination of factors that maximized flexural performance while minimizing variability. Response analysis revealed that cement content exhibited the largest delta (0.65 MPa), making it the most influential parameter within the investigated range. Mound soil replacement ranked second, followed by superplasticizer dosage, while water–cement ratio showed the smallest variation among the tested levels. The optimized mix produced concrete of flexural strength greater than the control concrete with 3.5% while achieving significant cement replacement. The findings confirm that the integration of optimized mound soil replacement and superplasticizer dosage can improve mechanical efficiency and durability potential of binary concrete. The study provides a practical optimization framework for producing environmentally sustainable structural concrete using locally available supplementary cementitious materials.