Comparative mechanical behaviors of four fiber-reinforced sand cemented by microbially induced carbonate precipitation

Microbially induced carbonate precipitation (MICP) has been found promisingly to improve soil mass properties with the environmentally friendly biogeochemical process, while MICP-treated soils show brittleness. Discrete fiber inclusion is an effective way to enhance soil ductility. In this study, we collaboratively utilized these two techniques for soil reinforcement. Mechanical behaviors including permeability, unconfined compressive strength (UCS), splitting tensile strength (TS) of biocemented sand reinforced by different contents (i.e., 0–1.8% by sand weight) of carbon fiber (CF), basalt fiber (BF), polypropylene (PP) fiber, and polyester (PET) fiber were accessed and compared. The microstructures of samples were also investigated by X-ray diffraction and scanning electron microscopy. It was found that fiber inclusions had a positive effect on the amount of precipitated calcium carbonate, and furthermore calcium carbonate type would not be changed by the introduction of four fibers. Besides, the beneficial effect of fibers on UCS was most pronounced at approximately 1% fiber volume fraction for four fibers, while permeability and TS were improved with the increase in fiber content. On the whole, the order of performance for the four fibers was as follows: CF > BF > PP > PET, evaluated by the improved behaviors of permeability, strength, and ductility for fiber-reinforced, biocemented sand. While taking cost into account, BF was the most cost-effective material among the four fibers.