CBR Characteristics of Kaolin-Simulated Clay Type Subgrade Stabilised with Cement, Lime, Poly-Fibre and Ionic Compounds mix

Abstract

Soil chemical stabilisation is an effective soil improvement method involving the blending of hydraulic binder with an existing soft soil to enhance the geotechnical properties for improved mechanical performance. Arguably time- and cost-saving as well as less labour-intensive with minimum skill requirement, it is a favourable solution to the construction of rural and farm roads in often economically challenged and resources deprived regions, especially for sites overlying soft grounds like clay deposits. The present study explores the feasibility of stabilising clay type subgrade with a proprietary hydraulic binder admixed with fibrillated polypropylene fibres. The binder—0.9% fibre mix was blended with the base clay of kaolin at optimum water content, in dosages of 0, 1.5 and 4.0% per dry weight of the soil. Soaked and unsoaked CBR tests were carried out on the stabilised specimens at intervals of 3, 7, 14 and 28 days in duplicates to attain the targeted minimum CBR value of 5% stipulated by Malaysian Public Works Department. Stabilisation dosage of 1.5% was found to be inadequate under soaked conditions even with prolonged curing up to 28 days. It was only at 4% dosage that the 3-day old soaked specimen could meet the minimum requirement. 1.5% dosage treatment for the unsoaked specimens recorded CBR values of 12.1–25.0% after curing for up to a week, while a fortnight curing with the 4% dosage specimen raised the CBR value to >30. Overall, the soaked specimens attained about half the strength of the unsoaked ones, with 14 days observed to be the threshold before the strength increment rate plateaued. In summary, the binder-fibre mix could effectively strengthen the clay soil with higher dosages offsetting the curing time, though subject to dry or soaked curing conditions.