Mechanical behaviors and their correlations of ultra‐high‐performance fiber‐reinforced concretes with various steel fiber types

The mechanical behaviors and their correlations of ultra‐high‐performance fiber‐reinforced concretes (UHPFRCs) with various steel fiber types were highlighted in this investigation based on the experiment combined with sectional analysis. Under compression, five fiber types with 2.0 vol% were investigated as follows: no fibers (PL), long twisted fibers (LT), long hook fibers (LH), long smooth fibers (LS) and hybrid fibers (HB, 1% twisted blended with 1% short smooth fibers). The LT revealed the highest compressive strength and strain capacity whereas the PL exhibited the lowest ones. Compared to the PL, the HB produced significant enhancements in strength, elastic modulus and deformation capacity under compression, tension and bending. The order in effectiveness of strength enhancement owing to additional hybrid fibers was as follows: bending > tensile > compressive loading. Based on sectional analyses, the enhancements in moment resistance of UHPFRC beams were closely correlated with higher compressive strength and smaller compressive strain capacity. Besides, the condition for first cracking at the bottom of UHPFRC beam was explored. Finally, a simplified model, based on the tensile response of UHPFRCs, for predicting the flexural resistances of the UHPFRC beams was proposed and validated.