Subgrade Soil Stabilization Using Stone Dust and Coarse Aggregate: A Cost Effective Approach

Abstract

Pavement construction tends to be relatively expensive in areas where subgrade soil is poor. Improvement in soil properties by replacement of the poor subgrade soil may not always be an economical solution. Keeping this into consideration, an experimental study was carried out on three types of fine-grained soil to demonstrate an economical solution by mechanical stabilization of the subgrade soil with stabilizers such as coarse aggregate of 10 mm size and stone dust. The effect of mechanical stabilization on Maximum Dry Density (MDD), Optimum Moisture Content (OMC) and California Bearing Ratio (CBR) was investigated. The study revealed that on the addition of the stabilizers with subgrade soil, the CBR value and MDD increased while OMC decreased. IRC: 37-2012, the standard for the thickness design of flexible pavements in India, specifies the use of select soil of minimum CBR 8.0% when traffic on the road is 450 commercial vehicles per day or higher. This desired value of CBR under soaked condition was obtained by the addition of 30% stone dust, or 20% of 10 mm size coarse aggregate, or 10% stone dust + 10% coarse aggregate of 10 mm size by mass of dry soil. This mechanical stabilization resulted in increase in soaked CBR value by 32.4%–194.7% for three types of fine-grained soils considered in the study. The mechanical stabilization with coarse aggregate or stone dust is also found to be more economical as compared to replacement of the soil with good soil of desired CBR value by more than 50%.