The California bearing ratio and unconfined compressive strength of clay–palm kernel shell mixtures

Palm Kernel Shell (PKS) is a by-product of the palm oil processing industry that is typically located in areas with very soft soil, particularly in South Kalimantan. It has been extensively studied as a replacement for concrete granular material. Hence, research into the potential use of PKS as a supplement to stabilize soft clay is required. This study aimed to investigate the California Bearing Ratio (CBR) and unconfined compressive strength (UCS) of compacted soft clay mixed with PKS. The clay was taken from a location around Banjarmasin. The sizes of PKS were 4.75mm (i.e. sieve No. 4) and 2mm (i.e. sieve No. 10) for CBR and UCS tests, respectively. Based on the dry mass, the clays was mixed with a PKS content of 2.5%, 5%, 10%, 15%, and 20%. The CBR and UCS tests were performed to the compacted specimens. The presence of PKS resulted made it easy in compacting the soft soil and increasing the CBR and UCS of the mixtures. The maximum CBR and UCS were obtained at the highest density (i.e. a PKS content of 2.5%). The values increased 1.5 and 3 times higher for CBR and UCS, respectively, as compared to the soil without PKS.