Title: Investigation on fracture behavior of cementitious composites reinforced with aligned hooked-end steel fibers

Abstract

Aligning steel fibers is an effective way to improve the mechanical properties of steel fiber cementitious composites (SFRC). In this study, the magnetic field method was used to prepare the aligned hooked-end steel fiber cementitious composites (ASFRC) and the fracture behavior was investigated. In order to achieve the alignment of steel fibers, the key parameters including the rheology of the mixture and magnetic induction of electromagnetic field were theoretically analyzed. The orientation efficiency factor of ASFRC and SFRC was 0.8 and 0.58, respectively. The results showed that, compared with SFRC, the cracking load and the ultimate load of ASFRC were increased about 24–55% and 51–86%, respectively, depending on the fiber addition content. In addition, the flexural tensile strength and residual flexural strength of ASFRC were found to increase up to 105% and 100%, respectively. The orientation of steel fibers also has a significant effect on energy consumption. The fracture energy of ASFRC was 56–70% greater than SFRC and the reinforcement effect of hooked-end steel fiber was higher than straight steel fiber. It was concluded that the fracture properties were enhanced significantly by the orientation of steel fibers. The fractural properties of ASFRC with Vf = 0.8% were found to be superior or equal to those of SFRC with Vf = 1.2%, which confirmed the advantage of ASFRC over SFRC and obtained high fracture properties, at a lesser amount of steel fibers, compared to SFRC. The fibers in the fracture surface showed that not only was the number of fibers of ASFRC higher than that of SFRC, but also the orientation efficiency factor of ASFRC was superior to SFRC, which explains the improvement of fracture behavior of ASFRC.