keywords: Concrete, cassava peel ash, egg shell powder, compressive strength
The major problem facing the world today is environmental pollution. Production of Portland cement causes the emission of carbon dioxide resulting to environmental pollution and global warming. This research is on the effect of cassava peel ash (CPA) and egg shell powder (ESP) as partial replacement of cement in concrete production. The cassava peel (CP) used was sourced from a local industries while the egg shell (ES) used was sourced from bakeries and restaurants. The CP was sun dried, burnt and sieved through a 75 µm sieve, while the ES was washed, sun dried, ground and sieved through a 75 µm sieve, and both materials were characterized by X-Ray Fluorescence (XRF) analytical method. The consistency, setting times and drying linear shrinkage of cement paste with CPA and ESP of 0, 5, 10, 20, 30 and 40%, respectively by weight of cement were investigated in accordance with standard procedures. CPA and ESP were mixed in a proportion of 10:90, 20:80, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80 and 10:90, respectively for the partial replacement of 0, 5, 10, 20, 30 and 40%, respectively by weight of cement. A total of six hundred and seventy five numbers of 150 mm cubes of hardened concrete were tested for compressive strength at 3, 7, 28, 56 and 90 days of curing in accordance with standard procedures. The results of the investigations showed that CPA was predominantly of Silicon oxide (56.73%) and a combined SiO2, Al2O3 and Fe2O3 content of 66.75%; and the result of the investigations showed that ESP was predominantly of Calcium oxide (52.75%) and combined SiO2, Al2O3 and Fe2O3 content of 0.22%. The addition of CPA and ESP in concrete production showed slight increase in compressive strength with increase in CPA/ESP additive up to 10% and decrease in compressive strength with further increase in CPA/ESP content. The 28 days compressive strength of concrete containing 10% CPA/ESP content was 6.4% more than normal and 10% CPA/ESP would be considered as the optimum percentage replacement; while that of concrete with 20% CPA/ESP content was 14.9 % less than normal.