Eco-Friendly Innovation in Soft Soil Stabilization: Combining Fine Pumice, Aluminium Hydroxide, and Lime to Enhance Road Bearing Capacity

Abstract

Soft soil is a material with low bearing capacity that often poses a major challenge in road construction, particularly in areas with high water content. This study aims to enhance the bearing capacity of soft soil through chemical stabilization using a combination of pumice, aluminium hydroxide (AH), and lime, with lime content variations of 2%, 4%, and 6%. The soft soil samples were collected from Subaim Village, East Halmahera, which naturally has a CBR value of 4,49% (categorized as "Poor to Fair") and is only suitable for use as a subgrade layer. Testing was conducted in accordance with ASTM standards on specimens soaked for 3 to 28 days to assess the impact of lime content and curing duration on the CBR value. The results showed that the addition of lime significantly improved the CBR value compared to the natural soil. At 2% lime content, the CBR value increased from 9,90% to 26,09%, while 4% lime produced the highest CBR value of 33,28%, representing an improvement of over sevenfold compared to the natural soil. Lime at 6% resulted in a CBR value of 27,89%, but it was less efficient compared to 4% lime. Based on CBR value classification, stabilization with 4% lime is categorized as "Good" and can be used as a base or sub-base layer for road construction under medium to heavy traffic loads. This research demonstrates that the combination of pumice, Al(OH)₃, and lime is an effective, environmentally friendly, and economical local material alternative for improving the bearing capacity of soft soil. It also offers a sustainable solution for road infrastructure development in remote areas.