Guinea Corn Husk Ash (GCHA) was a converted product of Guinea Corn Husk (GCH) that was incinerated up to a temperature of 600OC. The husk is a common agro-waste in Northern Nigeria. The GCHA was used to partially replace Ordinary Portland Cement (OPC) in concrete. The use was expected to reduce environmental nuisance and cost on cement. The replacement levels of 0%, 5%, 10%, 20%, 30% and 40% ash were used. The chemical constituents of the GCHA as determined from an X-Ray diffraction analyzer included SiO2 (85.4%), K2O (4.01%), Fe2O3 (0.64%), CaO (2.04%) and NaO2 (0.98%). SO3 and AI2O3 were not detected. The combined percent of SiO2, Al2O3 and Fe2O3 of 86.04% is above the 70% benchmark for a pozzolana material. Also SO3 and NaO2 fall below the maximum allowable values of 4% and 1.5% respectively. The fresh concrete had slump values that ranged from 11mm for 0% cement replacement to 3.6% for 40% replacement. The hard concrete had flexural strength that was measured as Modulus of Rupture that ranged from the highest value of 4.61N/mm2 at 0% replacement to the least value of 3.19N/mm2 at 30% replacement after 56 days of curing. The density values equally decreased at an average of 3.3%. The trend showed that GCHA did not improve flexural strength nor increased the density of concrete produced with it. The concrete may however find use in mass concreting and in hot weather.
Key words: Guinea Corn, Husk Ash, Flexural Strength, Cement, Concrete, Pozzolana.