Polypeptide additives for improving the performance of microbially induced calcite precipitation (MICP) sand consolidation

Abstract

Recognizing the limitations of Microbially Induced Calcite Precipitation (MICP) for sand consolidation, particularly the insufficient mechanical strength and the uneven distribution of precipitated calcite, our research takes an innovative approach. For the first time, we compare the potential of various polypeptide additives, including polylysine, polyaspartic acid, and polyglutamic acid, to enhance the MICP process. The optimal polypeptide was determined as polylysine, which could increase sand samples’ unconfined compressive strength (UCS) by 35.03% after MICP treatment. The optimal polylysine concentration is 100 mg/L, and the cementing liquid cost increased by only 3%. When the polylysine concentration exceeded 100 mg/L, the UCS of sand-solidified samples decreased. Environmental scanning electron microscope (ESEM) images showed that calcium carbonate and sand were bonded more tightly with polylysine added, and the distribution of calcium carbonate was uniform in the sand samples treated by MICP. X-ray diffractometer (XRD) showed calcium carbonate’s crystal form is calcite. This research signifies a crucial step forward in optimizing MICP for sand consolidation, potentially transforming applications in construction, geotechnical engineering, and environmental remediation.