PHYSICAL, MECHANICAL, AND MICROSTRUCTURAL ANALYSIS OF CONCRETE CONTAINING COW BONE ASH AT CALCINATION 900°C TEMPERATURE

ABSTRACT This study investigates the physical, mechanical, and microstructural properties of concrete containing cow bone ash (CBA) calcined at 900°C as a partial replacement for cement. The increasing demand for sustainable construction materials has driven research into agricultural and animal waste ashes as supplementary cementitious materials. Cow bone, primarily composed of hydroxyapatite and calcium phosphate, was calcined at 900°C, ground, and sieved to obtain CBA. Concrete mixes were prepared with CBA replacing 0%, 5%, 10%, 15%, and 20% of ordinary Portland cement by weight, while maintaining a constant water-cement ratio. Physical tests conducted included slump, density, water absorption, and porosity. Mechanical performance was evaluated through compressive strength, split tensile strength, and flexural strength tests at 7, 28, and 56 days of curing. Microstructural analysis was performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to assess hydration products, pore structure, and interfacial transition zones. Results indicate that CBA at 900°C exhibits pozzolanic activity due to its high calcium oxide and silica content. Physical properties show a slight increase in water absorption and porosity with higher CBA content, while density decreases marginally. Mechanically, concrete with up to 10% CBA replacement achieved compressive and tensile strengths comparable to, or slightly higher than, the control mix at 28 days, attributed to improved packing density and secondary C-S-H formation. Replacements above 15% led to strength reduction due to dilution of cement content and increased porosity. SEM and XRD analyses confirm the presence of additional calcium silicate hydrate gels and a denser microstructure in 10% CBA mixes, whereas higher replacement levels showed more unreacted particles and microcracks. The findings suggest that cow bone ash calcined at 900°C can be effectively utilized as a partial cement replacement at 10% without compromising mechanical performance, offering an eco-friendly alternative that reduces cement consumption and valorizes waste. Further optimization of particle size and curing conditions is recommended to enhance performance at higher replacement levels.