Bond Behaviors between Sand-coated GFRP Rebar and Concrete in Different Surface Conditions

Based on tests of 27 Losberg pull-out specimens,the bond behaviors between sand-coated GFRP rebar and concrete in different surface conditions were systematically analyzed.Test results showed that the experimental bond stress-slip curves between GFRP rebar and concrete(τ-S curve) was divided into ascending stage,descending stage and oscillating stage,and the ascending stage could be divided into the micro-slippage stage and slippage stage;with larger rib spacing of sand-coated GFRP rebar,higher spacing between troughs of the oscillating stage was obtained;for two kind of the sand-coated GFRP rebar specimens with different surfaces,the failure modes included pullout failure and splitting failure;the bond strength of sand-coated GFRP rebar with concrete was 84.2%~98.6% of that of the deformed steel;compared with the Aslan-1 sand-coated GFRP rebar,the bond strength of Aslan-2 sand-coated GFRP rebar with finer,better-distributed and thicker sand was 10% higher;the bond strengths of the two kinds of sand-coated GFRP rebar with different surfaces decreased along with the increase of the rebar diameter and the reduction of the concrete strength.