Study on bond strength between steel-polypropylene hybrid fiber reinforced concrete and deformed bar under cyclic loading

In order to study the cyclic bond strength between the steel rebar and steel-polypropylene hybrid fiber reinforced concrete (HFRC), a total of 36 specimens were designed by means of pull-out test taking the effects of volume fraction and aspect ratio of steel fiber (SF) and polypropylene fiber (PF) into consideration. The results show that the introduction of hybrid fibers has a synergetic effect on improving the bond strength, and SF exhibits a more pronounced influence. For the HFRC specimen, whose volume fraction and aspect ratio of PF were 0.15% and 167, the bond strength is increased by 20.57% and 14.75% respectively, when the volume fraction of SF varies from 0.5% to 1.5%, and 30 to 80 for the aspect ratio. However, no significant influence is observed when the volume fraction and aspect ratio of PF varies. Moreover, when comparing with the SFRC, PFRC and PC specimens, HFRC specimen having SF of 1.5% in volume fraction and 60 in aspect ratio, and PF of 0.15% in volume fraction and 167 in aspect ratio exhibits higher bond strength, and the improvement could reach up to 14.64%, 31.37% and 46.55% respectively. Furthermore, based on the theory of thick-walled cylinder and actual stress state, a modified model was proposed to calculate the bond strength between steel rebar and HFRC. The analytical solutions were then validated by the results from current study and other literatures. © 2017, Editorial Office of Journal of Building Structures. All right reserved.