COMPRESSIVE STRENGTH

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

Fire exposure destroys concrete structures, and the cooling methods significantly impacts residual strength Rapid cooling, especially with water, may cause additional damage due to thermal shock, yet limited studies compare air- and water- cooling effects. In order to determine which cooling technique best maintains structural integrity, this study will examine how various techniques affect the breaking strength of Grade 30 concrete exposed to temperatures of 200°C, 400°C, and 600°C. This study involves the preparation of Grade 10 concrete specimens, which were cured for 28 days before being subjected to elevated temperatures of 2000C 400C and 600°C in a controlled furnace. After exposure, the specimens were cooled using air and water to compare the effects of each method on compressive strength. The compressive strength of all samples was tested using a compression testing machine, and the results were analyzed through tabular and graphical comparisons to evaluate strength reduction trends. The study revealed that compressive strength decreased with increasing temperature, with watercooled samples experiencing greater strength loss than air-cooled due to rapid thermal shock. At 600°C, Average water-cooled samples record 26.561 N/mm², while air-cooled samples record 28.014 N/mm², confirming that gradual cooling helps to retain more structural integrity. Based on these findings, air cooling is recommended as a safer and more effective method for post- fire concrete recovery. Further research should explore advanced cooling techniques to enhance fire resistance and durability.

All over Nigeria as well as to the overseas the fuel oils as well as crude oils are transported through distribution pipes, tankers cargo ships. Although the processes are well laid out to avoid leakages of pipes, accidents of service tankers these events still happens on a regular bases especially in the niger delta region of the country where pipe vandalism due to oil bunkery is on the rise. All these processes leads to the leakages of fuel oils e.g kerosene which eventually settles on coastal waters. The leaked oil products would result in contaminating the water which are used in the concrete mortar and the sandcrete industry which are the cement dependent industry. In this study, the effect of water contaminated with kerosene on the compressive strength of conventional normal ordinary Portland cement has been evaluated in various exposure conditions. Kerosene (0, 2, 4 and 6%) by weight of water) was used to contaminate water to prepare cement mortar cubes specimens. A number of nine uncontaminated samples were prepared with fresh water. A number of nine samples each were prepared with contaminated water at 2%, 4%, 6% Kerosene replacement. Three samples each of percentage replacement and three uncontaminated samples were crushed at the age of three days, seven days and 28 days of curing. From the results gotten the maximum reduction in the compressive strength of 9.21% occurred at the six percentage contamination at the age of seven days. From results obtained it was seen that as the percentage of contamination increase the compressive strength decreased.