GEOTECHNICAL PROPERTIES OF LATERITIC SOIL STABILIZED WITH CASSAVA PEEL ASH AND STEEL DUST

The management of solid waste like steel dusts is a major challenge in Nigeria. Cassava Peel Ash (CPA) is a good pozolan as established from past studies. In this study, the geotechnical properties of weak lateritic soil stabilized with CPA and steel chips was investigated. Cassava peels of variety UMUCASS42 were collected from a local cassava processing factory in OkeBaale, Osogbo, Osun State. They were sundried, calcinated at 700oC and its chemical composition (Calcium, Silicon, Iron and Aluminium Oxides) were determined using XRay Fluorescence (XRF) Analyzer. Three lateritic soils samples A, B and C from 7o28ʹ46ʺN 4o34ʹ45ʺE, 7o34ʹ55ʺN 4o24ʹ47ʺE and 7o44ʹ54ʺN 4o31ʹ10ʺE, respectively were used. The geotechnical properties which included Moisture Content, Specific Gravity, Particle Size Analysis (percentage passing sieve no 200), Plastic Index (PI), Optimum Moisture Content (OMC), Maximum Dry Density (MDD) and California Bearing Ratio (CBR) of lateritic soil were determined at natural state. The lateritic soils were stabilized at 4% fixed steel dusts and at 0, 2, 4, 6 and 8% of CPA by dry unit weight of the soil samples. The MDD, CBR, OMC and Unconfined Compressive Strength (UCS) of the stabilized lateritic soil samples were determined. Analysis of Variance (ANOVA) at 5% level of significance was used to determine the effects of varying percentage of CPA with steel chips. The Calcium, Silicon, Iron and Aluminium Oxide of CPA at 700oC were 10.51, 60.67, 4.91 and 4.56%, respectively. The natural moisture content, specific gravity, percentage passing sieve no 200, PI, OMC, MDD and CBR of soil samples A, B and C were 15.1%, 2.73, 42.1%, 11.3%, 22.2%, 1846 kg/m 3 , 6%; 10.1%, 2.8, 50.8%, 7.7%, 19.6%, 1702 kg/m 3 , 2% and 13.8%, 2.65, 42.1%, 11.3%, 15.1%, 2880 kg/m 3 , 4%, respectively. The corresponding values for MDD, CBR, OMC and UCS of stabilized soil samples A, B and C varied from 1938-2042 kg/m 3 , 8-10%, 18.4 22.2%, 186-305 kN/m 2 ; 1935-2144 kg/m 3 , 4-6%, 16.8 -19.6%, 195–295 kN/m 2 and 2880-3020 kg/m 3 , 5-8%, 11.8-15.1%, 159-230 kN/m 2 , respectively. There was significant effect of varying percentage of admixture (CPA and steel chips) for stabilization on PI (P = 0.1986>0.05). The composite of CPA and steel chips is a good stabilizer for poor lateritic soil. Stabilization of weak lateritic soil with 4% of the composite can be used for base course in highway construction work. Keywords— Cassava, steel chips, laterite, stabilization