Abstract
This study investigates the effect of palm oil fuel ash (POFA), an agro-industrial by-product, as an additive partial replacement for cement in stabilizing laterite cubes, with a focus on enhancing compressive strength and reducing water absorption while promoting sustainable construction practices. The aim is to evaluate POFA's potential as a pozzolanic additive to mitigate the environmental and economic drawbacks of traditional cement use in lateritic soil stabilization, particularly in tropical regions like Nigeria where laterite and POFA are abundant. The specific objectives include: characterizing the physical and chemical properties of laterite soil, ordinary Portland cement (OPC), and treated POFA; assessing the compressive strength of stabilized laterite cubes at curing ages of 7, 14, and 28 days for POFA replacement levels of 0%, 10%, and 20% by weight of cement; evaluating water absorption characteristics at 28 days across these replacement levels; determining the optimal POFA dosage for the best balance of strength and durability; and comparing the results against civil engineering standards to validate practical applicability. Methodologically, laterite soil was sourced from Benin City, Nigeria, air-dried, and sieved through a 4.75 mm mesh to remove contaminants. POFA was obtained from a local palm oil mill, sun-dried, and finely ground to pass a 75 μm sieve, ensuring high pozzolanic activity due to its silica content (58.4% SiO₂). OPC conforming to ASTM C150 was used as the primary binder. Mix designs followed an additive approach, with laterite as the base (100%) and cement/POFA added in proportionsof 0, 10 and 20%. A water-binder ratio of 0.55 was maintained, and a total of 63 cubes (100 mm × 100 mm × 100 mm) were cast. Specimens were demolded after 24 hours and cured via full water immersion at 27 ± 2°C for the specified periods. Testing involved compressive strength and water absorption calculated as the percentage weight gain after 24-hour immersion. Material characterization included specific gravity (laterite: 2.65, cement: 3.15, POFA: 2.42), fineness, particle size, and oxide composition via X-ray fluorescence. Results indicate that POFA significantly influences both physical and mechanical properties. Chemically, POFA qualifies as a Class F pozzolan per ASTM C618. Dry density andWater absorption were done which gave its higher value at 10%. Compressive strength development showed marked improvements with POFA incorporation. The unstabilized control (100% laterite) yielded only 1.74 N/mm² at 28 days, unsuitable for structural use. Cement alone boosted strength to 3.93 N/mm² (10% cement) and 5.40 N/mm² (20% cement). The synergistic effect was most evident in mixes with both cement and POFA due to pozzolanic enhancement, filler effects, and accelerated hydration. Strength gains were delayed but sustained in POFA mixes, with 7day strengths lower but surpassing controls by 28 days. Overall, 10% POFA replacement optimized performance, meeting requirements for non-load-bearing applications. In conclusion, POFA at 10% replacement level is an effective, sustainable additive for laterite stabilization, reducing cement consumption by up to 50%, repurposing waste to lower environmental pollution and embodied CO₂, and cutting costs without compromising durability. This supports circular economy principles and SDGs 11 and 12. Recommendations include further field trials for long-term durability, exploration of higher POFA fineness or activation methods to extend optimal replacement beyond 10%, and policy incentives for POFA adoption in low-cost housing. Future studies could incorporate additional admixtures or assess resistance to environmental factors like acid attack or freezethaw cycles to broaden applications in diverse climateThis study investigates the effect of palm oil fuel ash (POFA), an agro-industrial by-product, as an additive partial replacement for cement in stabilizing laterite cubes, with a focus on enhancing compressive strength and reducing water absorption while promoting sustainable construction practices. The aim is to evaluate POFA's potential as a pozzolanic additive to mitigate the environmental and economic drawbacks of traditional cement use in lateritic soil stabilization, particularly in tropical regions like Nigeria where laterite and POFA are abundant. The specific objectives include: characterizing the physical and chemical properties of laterite soil, ordinary Portland cement (OPC), and treated POFA; assessing the compressive strength of stabilized laterite cubes at curing ages of 7, 14, and 28 days for POFA replacement levels of 0%, 10%, and 20% by weight of cement; evaluating water absorption characteristics at 28 days across these replacement levels; determining the optimal POFA dosage for the best balance of strength and durability; and comparing the results against civil engineering standards to validate practical applicability. Methodologically, laterite soil was sourced from Benin City, Nigeria, air-dried, and sieved through a 4.75 mm mesh to remove contaminants. POFA was obtained from a local palm oil mill, sun-dried, and finely ground to pass a 75 μm sieve, ensuring high pozzolanic activity due to its silica content (58.4% SiO₂). OPC conforming to ASTM C150 was used as the primary binder. Mix designs followed an additive approach, with laterite as the base (100%) and cement/POFA added in proportionsof 0, 10 and 20%. A water-binder ratio of 0.55 was maintained, and a total of 63 cubes (100 mm × 100 mm × 100 mm) were cast. Specimens were demolded after 24 hours and cured via full water immersion at 27 ± 2°C for the specified periods. Testing involved compressive strength and water absorption calculated as the percentage weight gain after 24-hour immersion. Material characterization included specific gravity (laterite: 2.65, cement: 3.15, POFA: 2.42), fineness, particle size, and oxide composition via X-ray fluorescence. Results indicate that POFA significantly influences both physical and mechanical properties. Chemically, POFA qualifies as a Class F pozzolan per ASTM C618. Dry density andWater absorption were done which gave its higher value at 10%. Compressive strength development showed marked improvements with POFA incorporation. The unstabilized control (100% laterite) yielded only 1.74 N/mm² at 28 days, unsuitable for structural use. Cement alone boosted strength to 3.93 N/mm² (10% cement) and 5.40 N/mm² (20% cement). The synergistic effect was most evident in mixes with both cement and POFA due to pozzolanic enhancement, filler effects, and accelerated hydration. Strength gains were delayed but sustained in POFA mixes, with 7day strengths lower but surpassing controls by 28 days. Overall, 10% POFA replacement optimized performance, meeting requirements for non-load-bearing applications. In conclusion, POFA at 10% replacement level is an effective, sustainable additive for laterite stabilization, reducing cement consumption by up to 50%, repurposing waste to lower environmental pollution and embodied CO₂, and cutting costs without compromising durability. This supports circular economy principles and SDGs 11 and 12. Recommendations include further field trials for long-term durability, exploration of higher POFA fineness or activation methods to extend optimal replacement beyond 10%, and policy incentives for POFA adoption in low-cost housing. Future studies could incorporate additional admixtures or assess resistance to environmental factors like acid attack or freezethaw cycles to broaden applications in diverse climate