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OMISANDE, LAWRENCE A, Volume 4 Issue 1, 2020 Pages 13-20, Published: 2021-10-10


The rapid growth of Ilaro and its environs have led to an increase in construction activities in the area. These projects require quality and stable earth for its implementation. However, large areas are covered with highly plastic and expansive soil, which is not suitable for such purpose. Consequently, this research was undertaken to investigate and improve the engineering properties of the black cotton soils of Ilaro and its environs. In Experimental investigation, the soil-Fly ash mixtures were prepared by mixing 0%,10%,20%,30%, 40% and 50% of fly ash (by weight).All these mixtures were tested in the laboratory for their index properties, compaction characteristics and California Bearing Ratios in accordance with British standard (BS 1377-1990). From the test results it was identified that addition of fly ash decreases plasticity and improves strength characteristics. Addition of 30-40% attains higher CBR values and improved swell characteristics. The study concludes that fly ash has a good potential to be used as an additive for improving the engineering properties of black cotton soils. The research recommended 30% of fly ash content for improving the engineering properties of BCS and to make it suitable in many civil applications