A Study on Crushed Coconut Shells as Stabiliser to Soil

Abstract

Road construction over soft subgrade soil is a major issue affecting cost and scheduling of highway projects. Many techniques have been conducted to strengthen the highway soil subgrade. One of them are using additives such as coconut shells, rice husk ash, stone dust, and fly ash. to strengthen the soil. The strength of the subgrade is commonly expressed as California Bearing Ratio (CBR). In this study, the crushed coconut shells (CCS) of 65 mm to 10 mm ranges of size was mix with the laterite soil. A series of unsoaked CBR test were conducted with an addition of 1, 2, 3, 4, 5, 6, 7 and 8% of CCS to determine the strength of the stabilized laterite soil. The laterite soil is classified as sandy SILT of high plasticity (MH) according to British Standard Classification System (BSCS). The results show that the CBR values of the stabilized soil increase with an increasing percentage the CCS. The stabilized soil with 4% CCS is the highest CBR value, 27.5%. The CBR% then decreasing as further additional of CCS %. The stabilised soil with an 8% CCS content had the lowest CBR value at 5.25%, which is lower than the unstabilised laterite soil’s CBR value. It is concluded that the additions of CCS have greatly improved the soil strength with the increment increase of CBR value. Hence CCS has a good potential for upgrading the CBR value of subgrade soil.