Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements

Concrete is a globally dominant construction material. This study addresses natural sand depletion and waste disposal challenges, aiming to statistically optimize concrete properties using Response Surface Methodology with ground waste bottle glass and cow bone ash replacements. Ordinary Portland Cement (OPC) conforming to BS 12 (1996) was used with river sand partially replaced by ground waste bottle glass (GWBG) and cow bone ash (CBA) in a 1:3:6 mix at 0.50 w/c ratio. Chemical and mineralogical analyses were performed using XRF and XRD, respectively. Workability was evaluated through slump and compacting factor tests, while compressive and tensile strengths were determined per BS standards. Experimental data were statistically optimized using Response Surface Methodology (RSM) in Design-Expert software. The X-ray fluorescence (XRF) analysis of Cow Bone Ash (CBA) revealed CaO, P₂O₅, SiO₂, MgO, and Al₂O₃ contents of 55.3%, 24.7%, 1.52%, 0.48%, and 0.35%, respectively. The X-ray diffraction (XRD) analysis identified hydroxyapatite, calcite, quartz, portlandite, sylvite, magnesite, and hematite with relative intensities of 72.6%, 15.4%, 4.8%, 3.2%, 1.5%, 1.0%, and 0.5%, respectively. The slump height and compacting factor values from 0% to 20% replacements of GWBG with CBA ranges from 55.47 to 34.58 mm and 4.59 to 4.61%, respectively. The 28-day compressive strength and splitting tensile strengths values were 14.85 to 14.41 MPa and 5.59 to 5.47 MPa, respectively. The optimal mix combination of 12.5% GWBG and 7.5% CBA recorded a slump height of 37.22 mm, compacting factor of 0.82, water absorption of 3.84%, compressive strength of 17.94 MPa, and splitting tensile strength of 6.05 MPa. The optimal mix of 12.5% GWBG and 7.5% CBA achieved the best balance of strength, durability, and workability, demonstrating excellent performance for sustainable and eco-efficient concrete production.