Sandcrete bricks, while widely used in affordable housing across developing countries, suffer from inherent limitations including low compressive strength and high moisture absorption. This study addresses these challenges by optimizing sandcrete brick mix proportions incorporating laterite and water treatment sludge (WTS) using Scheffe's (5,3) simplex lattice design. The research characterized laterite (46.2% passing 0.075 mm sieve, maximum dry density of 2.03 Mg/m³, optimum moisture content of 13.5%, and California Bearing Ratio of 90%), cement (28% consistency, 166/339 minutes initial/final setting time, 3.0 mm expansion, and 84.4 MPa compressive strength at 28 days), and fine aggregates (specific gravity 2.82, water absorption 2%). Thirty-five experimental mixes were formulated and tested for compressive strength and water absorption at 7, 14, and 28 days. Compressive strength results ranged from 0.29 MPa to 24.49 MPa at 28 days, with over 280 mixes exceeding the 7 MPa threshold suitable for structural applications. Water absorption ranged from 0.03% to 3.37%, with an inverse relationship observed between porosity and strength. The optimization model yielded a high coefficient of determination (R² = 99.24%), confirming excellent predictive capability. The optimized mix proportions (water 0.560, cement 1.070, WTS 0.651, laterite 0.549, and fine aggregate 2.761) achieved a maximum compressive strength of 14.99 MPa. The study concludes that laterite and WTS, when optimally proportioned using Scheffe's simplex lattice design, significantly enhance sandcrete brick performance while promoting sustainable construction practices through waste utilization.
Chukwuokwanuzo et al. (Fri,) studied this question.