Shear and Tensile Strength Measurements of ${\mathrm{CaCO}}_3$ Cemented Bonds between Glass Beads Treated by Microbially Induced Carbonate Precipitation

The particle-scale shear and tensile strength measurements of microbial-induced calcite precipitation (MICP) treatment have been investigated in this paper. Glass beads were used to represent sand particles. Three particle-scale test setups were developed to measure the tensile, shear, and cyclic shear strength of MICP-treated ${\mathrm{CaCO}}_3$ bonds between glass beads. Sporosarcina pasteurii bacterial cells were introduced to precipitate ${\mathrm{CaCO}}_3$ and form cementation bonds between glass beads. The preliminary particle-scale test (Test setup 1) was designed to measure the shear and tensile strength of ${\mathrm{CaCO}}_3$ bonds precipitated between glass beads mounted on optical fiber sensors with known properties. Shear and tension loads were applied to the ${\mathrm{CaCO}}_3$ bonds by the displacement actuators controlling the movement of movable stages. The improved particle-scale test setup (Test setup 2) was developed using a larger and stable reaction chamber, an automated injecting system, and stiff bending elements (instead of optical fibers) that were connected to glass beads to improve measurements. Deflections of the bending elements were measured to calculate the tensile and shear strength of the ${\mathrm{CaCO}}_3$ bonds using the beam theory. The enhanced particle-scale test setup (Test setup 3) was developed to directly measure the shear and tensile forces generated in ${\mathrm{CaCO}}_3$ bonds using load cells and LVDTs to investigate the monotonic and cyclic response of the ${\mathrm{CaCO}}_3$ bonds. For the tests using Test setup 3, the shear and tensile strengths were 378 and 446 kPa, respectively.