GEOPOLYMER STABILIZATION OF CLAY SOIL USING EFB ASH AND METAKAOLIN

Abstract

Clay soils with low bearing capacity can pose challenges in construction, requiring stabilization to improve their engineering properties. This study investigates the use of empty fruit bunch ash (EFB ash) and metakaolin as geopolymer-based materials for clay soil stabilization. Metakaolin:EFB ash ratios of 75:25, 60:40, and 50:50 were evaluated at binder contents of 10% and 15%. NaOH concentrations of 8 M, 10 M, and 12 M were used as alkaline activators, with curing periods of 52, 77, and 109 days. Unconfined compressive strength (UCS) was evaluated under unconfined axial loading. The untreated soil exhibited a UCS of 0.325 MPa, while the highest UCS after stabilization reached 3.291 MPa, obtained with a 50:50 metakaolin:EFB ash ratio, 10% binder content, 12 M NaOH, and 52 days of curing. This value represents an approximately 10.1fold increase compared with the untreated soil. The results show that the 50:50 metakaolin:EFB ash ratio and 10% binder content generally produced higher UCS values, while 10 M NaOH yielded the highest average UCS among the tested activator concentrations. The higher strength at the 50:50 ratio may be associated with interactions between metakaolin and EFB ash, although this mechanism requires further chemical and microstructural verification. Overall, the results indicate that the metakaolin and EFB ash combination has potential for clay soil stabilization, including applications such as subgrade and stabilized fills, subject to applicable technical requirements.