Influence of Fiber Content and Length on Engineering Properties of MICP-Treated Coral Sand

Microbially induced calcite precipitation (MICP) can improve the engineering properties of coral sand. The dry density, permeability, unconfined compressive strength (UCS), tensile strength, and microstructure were measured to investigate the effect of fiber addition on the engineering properties of MICP-treated coral sand and determine the corresponding microstructure. Apart from reducing the permeability and improving the dry density as well as UCS of the MICP-treated coral sand, the added fibers could improve the ductility, failure strain, and tensile strength of the MICP-treated coral sand. The added fibers increased the dry density of the MICP-treated coral sand from 1.38 g/cm(3) to 1.70 similar to 2.01 g/cm(3), reduced the permeability by 2 similar to 3 orders of magnitude, and improved the UCS to 2.78 similar to 21.65 MPa, whereas the tensile strength varied from 0.79 to 2.29 MPa. The fiber content affected the engineering properties of MICP-treated coral sand more significantly than the fiber length. The optimal content of fiber addition was 0.2%, whereas the optimal fiber length was 9 or 12 mm. The improvement of the engineering properties of MICP-treated coral sand with fiber addition can be interpreted by the coating, bonding, and interlacing effects observed in scanning electron microscopy (SEM) images.