An Experimental Study on Enzymatic-Induced Carbonate Precipitation Using Yellow Soybeans for Soil Stabilization

In this study, the applicability of enzymatic-induced carbonate precipitation (EICP) using yellow soybean for soil stabilization was investigated through laboratory tests. A comparison of carbonate precipitation efficiency between EICP using yellow soybean and microbial-induced carbonate precipitation (MICP) using ureolytic bacteria as a catalyst for urea hydrolysis was made through a series of tube precipitation tests. It was found that EICP can be an excellent alternative to MICP in terms of carbonate precipitation efficiency. In addition, the reinforcing effect of EICP using yellow soybean on soil specimens was investigated by measuring the unconfined compressive strength (UCS) and the amount of calcium carbonate precipitated with varying molarities of solutions and curing times. The results of the unconfined compression tests showed that the curing time (7, 14, 21, 28 days) had no significant effect on the strength enhancement when the molarity of urea–CaCl 2 solution was less than 1.5 M. However, for 3 M of urea–CaCl 2 solution, the UCS increased with curing time (7, 14, 21, 28 days), although the amount of calcium carbonate precipitated was not affected by curing time. In addition, it was confirmed that the strength increment ratio of specimens cured for 28 days under various mixing conditions linearly increased with calcium carbonate contents ranging from 0% to 5.13%. It is concluded that EICP using yellow soybean has a great practical potential as a soil stabilization method.