Effect of wool fiber addition on the reinforcement of loose sands by microbially induced carbonate precipitation (MICP): mechanical property and underlying mechanism

Animal fibers with α-keratin had obvious advantages of mechanical strength and durability on reinforced microbially induced carbonate precipitation (MICP)-cemented loose sands. Herein, wool fiber, α-keratin-rich animal fiber with high strength, was applied to reinforcement of MICP-cemented loose sands. The mechanical properties and underlying mechanism were experimentally explored. Results showed that adding 0.1 wt% wool fiber enhanced up to 3.34-fold the compressive strength and significantly improved the flexure resistance performance. The microstructural results revealed that wool fibers providing many nucleation sites for calcite precipitation not only significantly decreased the porosity of the specimen, but also effectively generated calcite and distributed fiber-bridging microstructure uniformly, resulting in a marked reinforcement of MICP performance. Further studies indicated that sand grains were cemented with calcite through the intermolecular hydrogen bonds HN–H … O–C(Si). This study first reports the potential and the underlying mechanism of animal fiber on improvement of MICP performance and provides new insight into enhancing mechanical behavior of MICP-cemented loose sands with fibrous proteins. Graphic abstract