CHARACTERIZATION OF SANDCRETE BLOCKS IN OGUN STATE, NIGERIA

Abstract

ABSTRACT Frequent building failure experience in Nigeria and many other countries necessitates the quality assurance of all building materials in circulation including sandcrete blocks. This study investigates the compressive strength and quality of sandcrete blocks produced in Ogun State, Nigeria. Sandcrete blocks, widely used in construction, are made from a mixture of sand, cement, and water. Laboratory tests conducted include sieve analysis, moisture content, silt/clay content, specific gravity, bulk density, organic matter content, compressive strength, water absorption, and microstructural analysis using X-ray fluorescence (XRF) and X-ray diffraction (XRD). The results revealed significant variations in the quality of sandcrete blocks across different locations in Ogun State, with many blocks failing to meet the minimum compressive strength requirements. The results reveal variations in block quality, with compressive strength tests showing the highest values in Obafemi Owode LGA (1.93 N/mm² for 225 × 225 × 450 blocks and 1.40 N/mm² for 150 × 150 × 450 blocks), while the lowest strengths were recorded in Ado-Odo/Ota LGA (0.17 N/mm² for 6-inch blocks) and Ifo LGA (0.40 N/mm² for both block sizes). Water absorption tests demonstrated similar disparities, with Likosi Simawa Sagamu LGA showing the best performance (7.64-11.29% absorption) compared to Ado-Odo/Ota LGA's worst results (9.44-18.07% absorption). Microstructural analysis through XRF and XRD revealed that sample X5, which demonstrated the highest compressive strength (1.93 N/mm²), benefited from an optimal chemical composition, particularly its high CaO (35.01%) and Fe₂O₃ (11.53%) content. These components facilitated robust cement hydration and the formation of strength-enhancing ferrite phases. Sample K3, with a medium strength of 0.9 N/mm², contained elevated SiO₂ (52%) and moderate CaO (23.13%), but its low iron oxide content limited potential strength gains from ferrite-related reactions while Sample A1, the lowest compressive strength (0.4 N/mm²), was characterized by a high muscovite concentration (52.5% XRD intensity), a mineral known for its weak properties that compromise structural integrity. These findings have critical implications for construction safety, as 68% of tested blocks failed to meet the NIS 87:2007 minimum compressive strength requirement of 1.2 N/mm², while 72% exceeded the 12% water absorption limit, significantly compromising structural integrity and durability. The study recommends immediate regulatory intervention, including standardized mix ratios (1:6 cement-sand), mandatory curing periods (minimum 28 days), and mechanized production methods to address these quality concerns and prevent potential building failures in the region.