COMPARATIVE ANALYSIS OF SELECTED STABILIZATION AGENTS FOR SUBGRADE SOIL

The lateritic soil which is the major material used in road construction sometimes may be unsuitable which leads to failure of the pavement profiles. This study therefore evaluated the use of hydrated lime, cement and bitumen in stabilizing lateritic soil. Lateritic soil samples were collected from proximal four (4) different borrow pits namely Odookun-Igbeti (OI), Gbemi-Igbeti (GI), Isafa-Kisi (IK), Yoyin-Kisi (YK) along Igbeti-Kisi Road, Oyo State, Nigeria. The stabilized soil mixture was prepared by using 2, 4, 6 and 8% hydrated lime, cement and bitumen by weight of soil samples, while the unstabilized sample served as control. The unstabilized and stabilized samples were subjected to Specific Gravity (SG), Particle Size Analysis (PSA), Liquid Limit (LL), Plastic Limit (PL), Maximum Dry Density (MDD), Optimum Moisture Content (OMC), and unsoaked California Bearing Ratio (CBR), in accordance with British Standard BS 1377: 1990. The SG and PSA values for the unstabilized samples obtained from OI, GI, IS and YK were 2.28, 2.41, 2.22, 2.47 and 35.14, 33.78, 41.10, 41.04%. LL and PL values were 33, 33, 19, 34% and 22, 17, 23, 14%, respectively. The corresponding MDD, OMC and unsoaked CBR were: 1.79, 1.90, 1.72, and 1.81 g/cm3, 15.0, 15.5, 18.9, 13.3%, and 18, 11, 4, 17%, respectively. The corresponding ranges of values for stabilized samples for the varying percentage of the stabilizing agents were: Lime: LL (33 - 36, 33 - 42, 39 - 43, 34 - 42%); PL (19 - 26, 17 - 27, 23 - 28, 14 -27%); MDD (1.67 - 1.95, 1.79 - 1.95, 1.64 - 1.76, 1.63 - 1.92 g/cm3); OMC (11.4 - 15.0, 11.0 -15.5, 11.5 - 18.9, 9.0 - 13.3 %); and CBR (48, 43, 17, 30%), respectively. For Cement: LL (33 -38, 33 - 38, 39 - 48, 34 - 48 %); PL (21 - 26, 17 - 26, 23 - 32, 14 - 30%); MDD (1.76 - 1.88, 1.76 - 1.90, 1.72 - 1.94, 1.73 - 1.82 g/cm3); OMC (10.9 - 15.0, 12.5 - 16.6, 12.6 - 18.9, 9.0 - 13.3 %); and CBR (45, 39, 29,31%), respectively. While for Bitumen: LL (30 - 34, 29 - 34, 38 - 41, 34 -38%); PL (17 - 24, 13 - 23, 17 - 24, 14 - 26%); MDD (1.67 - 1.95, 1.73 - 1.93, 1.72 - 1.93, 1.68 -1.92 g/cm3); OMC (11.4 - 15.0, 9.0 - 15.5, 13.0 - 18.9, 9.0 - 13.3%); and CBR (56, 41, 20, 25%), respectively. The study has shown that lateritic soil samples obtained from the four sites required stabilization based on geotechnical properties, hence the stability of the laterite soil samples were enhanced with hydrated lime, cement and bitume