STABILISATION OF TROPICAL BLACK CLAY USING CALCIUM CARBIDE RESIDUE AND COCONUT SHELL ASH AS ADMIXTURE

Abstract

A Tropical Black Clay (TBC), obtained by method of disturbed sampling, at a depth of between 0.5m to 1.5m, at Gwako village, Abuja, Nigeria, was treated with 0, 2, 4, 6, 8, and 10% each of Calcium Carbide Residue (CCR) and Coconut Shell Ash (CSA). Effect of the additives was investigated with respect to compaction characteristics (Maximum Dry Density-MDD and Optimum Moisture Content-OMC) and Unconfined Compressive Strength (UCS) cured at 1, 7, 14, 28, 60 and 90 days. Results of index properties of the soil indicated that it is classified under CH and A-7-5, according to Unified Soil Classification System (USCS) and American Association of State Highway and Transportation Officials (AASHTO) respectively. There was a general decrease in MDD of the treated soil with increase in dosage of the additives from 1.784 g/cm3 at 0% CSA and 0% CCR to a minimum value of 1.666 g/cm3 at 8% CSA and 4% CCR, while the OMC increased with increase in dosage of the additives from 18.0% at 0% CSA and 0% CCR to a maximum value of 23.7% at 4% CSA and 8% CCR. UCS of the treated soil showed general increase with increase in dosage of the both additives and curing period from 19.196 kN/m2 at 0% CSA and 0% CCR to a maximum value of 1194.972 kN/m2 at 0% CSA and 10% CCR after 90 days curing. It was therefore, concluded that, although the treated soil did not meet the 1710 kN/m2 UCS value require for base materials, the requirement of 687-1373 kN/m2 for sub-base materials was achieved within the composition considered and therefore could be used as sub-base materials for lightly trafficked roads.