The Effect of Nucleating Agents on Enzyme-Induced Carbonate Precipitation and Corresponding Microscopic Mechanisms

Plant urease has the advantages of high activity and small size in enzyme-induced calcium carbonate precipitation (EICP). However, there area lack of nucleation sites for calcium carbonate in EICP. Sucrose and sorbitol, which are readily available and inexpensive, have the potential to provide nucleation sites for EICP as nucleating agents. To explore the effects of the two nucleating agents on EICP, the productivity of calcium carbonate, unconfined compressive strength (UCS) and microscopic mechanisms were tested. It is found that the productivity of EICP can be increased as much as 5.1% by the addition of sorbitol with an optimal content of 5%, and the productivity of EICP can be increased as much as 12.3% by the addition of sucrose with an optimal of 4%. The UCS of EICP-treated sand increases by 2.2 times after being improved by sorbitol with a content of 5.2%, the CaCO₃ content of EICP-treated sand with sorbitol added increased by 1.5% compared to conventional EICP-treated sand. These results show that the two nucleating agents are effective for improving EICP. The SEM images verify that sorbitol/sucrose can compensate for the lack of nucleating sites in EICP and explicate the effect of nucleating agents on EICP.