Experimental study of the bond performance and mechanical response of GFRP reinforced concrete

• Bond performances and mechanical responses of GFRP concrete members were studied.
• The optimum GFRP bar is of 0.8d thread gap, 1 mm thread depth and is in favor of small diameter.
• GFRP beam has close bearing but inferior crack control capacity compared to steel reinforced one.

This study carried out laboratory investigations of mechanical behaviors of glass fiber reinforced polymer (GFRP) concrete and consisted of three test programs. It first obtained elastic parameters of GFRP bar and then conducted pull-out test to evaluate the bond performance of GFRP/steel bar with concrete. The test variables involved diameter, thread depth, thread width, embedment length of GFRP bar and cement strength, a total of 32 combinations. Test results indicate the optimum GFRP bar is with thread gap of 0.8-diameter, thread depth of 1 mm, and in favor of small diameter size. The GFRP reinforced specimens provide approximately 60% of bond strength benchmarked by the steel reinforced specimens but have much higher slip length. Lastly, four-point bending test was applied to five types of GFRP/steel reinforced concrete beams to investigate the mechanical responses of the beams until failure. Test results indicate at the same reinforcement ratio and geometric size, GFRP bar and steel bar have the same bearing capacities. However, the former is inferior to the latter in terms of crack control.