The influence of geometric characteristic on the pullout behavior of basalt FRP minibar embedded in concrete

Abstract With the increasing demand on structural toughness and energy absorption capacity, the addition of fiber to concrete has become an issue of significance. This paper studies the bond behavior of Basalt FRP (BFRP) minibar with straight, twisted and crimped geometric characteristics. The failure modes, pullout curves and bond strength were compared, and their interface degradation, damage evolution and failure mechanism between single fiber and concrete matrix were analyzed. Additionally, commercial steel fibers and polypropylene fibers were compared with the BFRP minibars to clarify the effect of fiber type on failure morphology, bond strength and interface properties. The results showed that the pulling out process for straight BFRP minibars, twisted BFRP minibars and crimped BFRP minibars was constituted by the elastic bonding stage, the partial de‐bonding stage, the complete de‐bonding stage and the pullout of fiber. The bond strength was composed of chemical adhesion and mechanical bond, where the mechanical bond play important role after the initial failure of chemical adhesion. The bond strength of crimped BFRP minibar, the hooked steel fiber, the indented polypropylene fibers and the twisted BFRP minibar were enhanced by 358%, 324%, 115%, and 54.5% compared to straight BFRP minibars. The interface bonding strengths improve with the increase of matrix strength. Dense microstructures of matrix improve the bond strength. The bond‐slip constitutive model was proposed for crimped, twisted and straight BFRP minibars with regression coefficient of 0.978, 0.891, and 0.992, respectively. Highlights Influence of fiber geometry and concrete strength on the pullout behavior Interface degradation, damage evolution and failure mechanism between minibar and concrete Bond‐slip constitutive model of straight, twisted and crimped BFRP minibars