Fracture of Interparticle MICP Bonds under Compression

Abstract

Microbiologically induced calcium carbonate precipitation (MICP), as a promising reinforcement technique, has been investigated extensively through element and model tests. However, tests on the particle-scale behaviors of MICP bonds are rarely conducted yet, which constrains the development of constitutive and numerical models of MICP-treated sands. In this paper, a set of devices is designed to form MICP bonds between spherical quartz beads (SQBs) and spherical calcareous beads (SCBs) and investigate the microscopic compression behavior of the interparticle MICP bonds in comparison with portland cement (PC) bonds. The experimental results reveal that the PC bonds are the strongest, whereas the MICP bonds between SQB are the weakest. A higher cementation degree leads to higher strength and smaller dispersion among parallel specimens, while a larger interparticle distance causes smaller strength and greater dispersion. Identified with force–displacement curves and optical photos, the PC-treated SQB specimens are dominated by brittle failure, the MICP-treated SQB specimens can present ductile or brittle failure, and possible grain crushing is observed in the MICP-treated SCB specimens. Scanning electron microscopy (SEM) images suggest better interfacial bonding for the MICP-treated SCB specimens than for the MICP-treated SQB specimens. Gravity-related inhomogeneity is observed in the MICP bonds, whereas a homogeneous dense microstructure is observed in the PC bonds.