Utilization of fibers in ultra-high performance concrete: A review

Fibers are essential in reinforcing the mechanical properties of ultra-high performance concrete (UHPC), particularly the tensile and flexural strength. This paper conducts a systematic review on the effect of fibers with different textures and geometry on the properties of UHPC from the following aspects: (1) the bond mechanism of steel fibers with the UHPC matrix; (2) the effect of fiber shape, fiber orientation and hybridization of steel fibers on the microstructure, failure mode, mechanical properties, autogenous shrinkage and durability of UHPC; (3) the reinforcing mechanism of synthetic fibers (polyvinyl alcohol fibers (PVA), polypropylene fiber (PP), polyethylene fibers (PE)), mineral fibers (basalt fibers, wollastonite fibers) and carbon fibers in UHPC and their effect on the performance of UHPC; (4) the use of hybrid fibers and their synergetic effect on the mechanical performance and shrinkage of UHPC. Finally, this paper discussed the further research trends of fibers in UHPC.