Effect of Palm Oil Fuel Ash on the Strength and Ammonium By-Product Removal of Biocemented Sandy Soil

Abstract

Enzyme induced calcite precipitation (EICP) or biocementation has rapidly evolved in the last decade as an environmentally friendly ground improvement technique. In EICP, plant-derived urease enzyme is used to trigger the hydrolysis of urea in the presence of calcium ions to produce calcium carbonate (CaCO3) precipitate within the soil matrix. Despite the advancement in soil improvement technology via biocementation, there are still concerns about the fate of the ammonium produced as one of the by-products. Therefore, this study performed an experimental investigation to ascertain that using palm oil fuel ash (POFA) might reduce the amount of ammonia produced as a result of biocementation. The soil was mixed with POFA at different percentages (1, 2, 3, 4 and 5%) by dry weight of the soil. The effectiveness of the treatment process was evaluated by conducting the unconfined compressive strength (UCS) and the ammonium removal efficiency. Results show that the strength and ammonium removal efficiency of the biocemented soil decreased and increased, respectively, with an increase in the percentage of POFA. The highest UCS of 161 kPa was obtained at 3% POFA content, while the lowest concentration of ammonium of 0.71 mg/L was at 5% POFA content.