Acid corrosion micro-macro mechanism of enzyme-induced carbonate precipitation (EICP) treated sandy soils

Carbon dioxide (CO 2 ) geological sequestration is an effective way to control CO 2 emissions, and the geological safety in CO 2 injection project is the most concern problem. Enzyme-induced carbonate precipitation (EICP) technique is believed as useful to overcome CO 2 leakage problem, but its main cementation matter, calcium carbonate, may be corroded by acidic CO 2 solution. Therefore, laboratory studies are necessary to investigate the acid corrosion and resistance of EICP treated sandy soils. In this study, the EICP specimens were immersed in acid solutions with different concentrations, and both mechanical strength and micro-macro structure were investigated based on mass loss, apparent analysis, unconfined compressive strength tests, SEM and XCT. The results indicate that the corrosive effect of acid solution on EICP specimens was obviously strengthened by the decrease in solution pH, the ablation of calcium carbonate destroyed the cementation-pore structure resulting in the gradual shedding of the outer layer of the specimens and the nearly linear decrease in unconfined compressive strength. After acid corrosion reaction, the EICP specimens were found with a large number of intergranular pores among calcium carbonate particles. This study reveals the evolution mechanism of acid corrosion of EICP specimens, providing a reference for the corrosion resistance of EICP.