Influence of Enzyme Induced Carbonate Precipitation (EICP) on the Engineering Characteristics of Expansive soil

Abstract

Enzyme induced carbonate precipitation (EICP) is a new bio-cementation technique that utilizes plant-sourced urease to catalyze urea degradation and reaction with calcium iron, resulting in the formation of calcium carbonate (CaCO₃) for soil improvement. EICP has considerable promise for novel and sustainable engineering applications such as soil strengthening, pollutant remediation, and other in situ field applications. In this study, the effect of EICP on the geotechnical characteristics of expansive soil is examined. A series of laboratory tests have been performed with an optimal concentration ratio of 0.75 mol/L. The outcomes of the compaction experiment indicated a slight increment in the dry density of the expansive soil from 15.78 to 16.71 kN/m³.Further, it diminished the optimal moisture content of the soil, decreasing it from 22.3 to 18.5%. The utilization of EICP improves the soil mechanical characteristics, reducing swelling pressure by 80% and increasing the UCS, cohesion, friction angle, unsoaked and soaked CBR by 66%, 44%, 49%, 441%, and 430%, approximately. Additionally, it leads to a significant decrease in soil permeability, approximately 63%. Moreover, SEM and XRD analysis confirmed the presence of CaCO₃ content in the treated soil. The experimental findings indicated that the EICP method holds promise in enhancing expansive soil within engineering projects.