Utilization of Coconut Shell Charcoal to Improve Bearing Capacity of Clay as Subgrade for Road Pavement

Abstract

Road construction on clay causes many problems with road damage because clay has a low bearing capacity and a large swelling value. The soil stabilization method was used to improve clay soil characteristics by adding cement, lime, fly ash, or other stabilizing agents. One of the stabilizing agents used in this study is coconut shell charcoal. The purpose of this study was to analyze the effect of adding coconut shell charcoal to the CBR value and the swelling index on clay soil. In this study, the coconut shell charcoal used was 0%, 4%, 8%, 12%, and 16% of the dry weight of the soil. The samples used were disturbed soil, and the curing period was 7 days. Testing the physical and mechanical properties of the soil (CBR and Swelling test) refers to the ASTM Standard. The results showed that the addition of coconut shell charcoal by 4% increased the bearing capacity and reduced the swelling index. An optimal CBR value of 14.69% was obtained for the addition of coconut shell charcoal by 4% with the unsoaked condition with a 7-day curing period. Whereas in the soaked soil condition, the optimal CBR value is 8.53% and the swelling value is 0.24%. Increasing the CBR value and decreasing the swelling value will cause the road construction layer to be more stable in supporting the load.