Fiber-reinforced microbially induced carbonate precipitation (MICP) for enhancing soil stability: Mechanisms, effects, and future prospects

Microbially induced calcium carbonate precipitation (MICP) is an emerging technology proposed for soil improvement in recent years. It has environmental protection and sustainability advantages. Reinforcing fiber can effectively improve the flexibility of MICP-treated sandy material. The MICP synergistic fiber solidified sand research results have attracted significant attention recently. This paper introduces the reaction mechanism and curing method of MICP, including injecting soaking, spraying, pre-mixing, single-phase, and step-by-step injection methods. It summarizes the effect of various fibers, including jute fiber, animal fiber, polypropylene fiber, carbon fiber, polyester fiber, and polyvinyl alcohol fiber (PVA), on the synergistic curing of sand. This research project summarized the following results: 1) The two-step injection method improves the uniformity of calcium carbonate distribution in the sample. 2) Adding fiber provided more adsorption sites for bacteria and increased nucleation sites; 3)The fibrous network structure of the sample, combined with the 'bridge' effect, is efficient in preventing cracks from expanding in soil samples; 4) The friction and cohesion between the fiber itself and the sand column improve the overall stability of the sand sample; 5) The coupling of fiber, sand, and generated calcium carbonate improves the flexibility and tensile strength (TS) of specimens; 6) For the two factors of fiber content and fiber length, the effect of fiber content on unconfined compressive strength (UCS) is greater than fiber length. Fiber type is influenced more than fiber length. Meanwhile, the development prospect of MICP synergistic fiber was pointed out, including 1) the influence of fiber pretreatment and modification on curing effect; 2) the fiber and sand mixed, uniform distribution method; 3) The method of mixing the fibers improves the properties of the cured specimens.