S. A. Adegbemileke

This research investigates the suitability of cow bone ash (CBA) as a partial replacement for ordinary Portland cement (OPC) in concrete production, with the aim of reducing cement consumption, lowering environmental impact, and promoting sustainable waste management practices in Nigeria. Cow bones, which constitute a major agricultural waste product, were processed into ash through controlled calcination and evaluated for their potential pozzolanic contribution in concrete. The study focused on assessing the effects of varying percentages of CBA on the fresh and hardened properties of concrete, particularly particle size distribution, workability, strength development, and durability. To achieve the objectives of the study, concrete mixes were prepared using a nominal mix ratio of 1:2:4 and a constant water–cement ratio of 0.50. Cow bone ash was used to partially replace cement at replacement levels of 0%, 5%, 10%, 15%, 20%, and 25% by weight. Laboratory tests were conducted in accordance with relevant British and ASTM standards. These tests included sieve analysis to determine particle size distribution, slump test to assess workability, compressive and flexural strength tests at curing ages of 7, 14, and 28 days, and water absorption tests to evaluate durability characteristics. The results showed that concrete containing 5–10% cow bone ash exhibited improved performance compared to the control mix. At these replacement levels, improved particle packing and additional calcium silicate hydrate (C–S–H) formation led to enhanced strength and reduced water absorption. However, workability decreased with increasing CBA content due to higher water demand, and replacement levels above 15% resulted in reduced strength and increased water absorption caused by higher porosity and unreacted ash particles. In conclusion, cow bone ash can be effectively used as a supplementary cementitious material at replacement levels of up to 10–15%, offering an environmentally friendly and cost-effective alternative to conventional cement in concrete production.

This study investigated the effect of nanosilica (NS) as a partial replacement for ordinary Portland cement (OPC) on the mechanical and durability properties of concrete. The aim was to assess the suitability of nanosilica in improving concrete performance and to determine its optimum replacement level for sustainable construction applications in Nigeria.Concrete was produced using a nominal mix ratio of 1:2:4 and a constant water–cement ratio of 0.5. Nanosilica was used to replace cement at levels of 0%, 1%, 2%, and 3% by weight. Tests carried out included slump test, setting time determination, compressive strength test, flexural strength test, and water absorption test. Statistical analysis of the results was performed using oneway analysis of variance (ANOVA).Results showed that workability increased with increasing nanosilica content, while both initial and final setting times decreased. Compressive and flexural strengths increased up to an optimum nanosilica content of 2%, where 28-day values of 24.4 N/mm² and 5.25 N/mm² were recorded, compared to 22.5 N/mm² and 4.67 N/mm² for the control mix. Water absorption reduced to 7.3% at 2% nanosilica replacement compared to 9.7% for the control, indicating improved durability. ANOVA results showed no significant differences in compressive strength, flexural strength, and workability (p > 0.05), while setting time showed significant variation (p < 0.05). The study concluded that 2% nanosilica replacement provided the best overall performance and is recommended for producing stronger and more durable concrete