Experimental study on the bonding performance between GFRP reinforcement and coal gangue concrete

To investigate the influence of different influencing factors on the bonding performance between glass fiber reinforced polymer reinforcement and coal gangue concrete, 48 GFRP reinforcement coal gangue concrete specimens were subjected to pull-out tests. The influence of factors such as coal gangue substitution rate, GFRP reinforcement diameter, coal gangue concrete strength, and anchoring length on the bonding performance between GFRP reinforcement and coal gangue concrete was analyzed. The results indicate that the failure modes of GFRP reinforcement and coal gangue concrete specimens include pull-out failure and splitting failure. The bond slip curve between GFRP reinforcement and coal gangue concrete can be roughly divided into three stages: ascent stage, descent stage, and residual stage. As the replacement rate of coal gangue increases, the ultimate bonding strength decreases. In the coal gangue concrete benchmark strengh C35 group, the replacement rate of coal gangue aggregate increases from 0% to 100%, and the ultimate bonding strength decreases from 5.5% to 25.2%, which is higher than the 4.7%-21.2% of coal gangue concrete benchmark strengh C50 group. Due to the influence of shear lag and Poisson's effect, the bond strength gradually decreases with the increase of reinforcement diameter. The ultimate bonding strength of 16 mm diameter is approximately 77% of that of 10 mm diameter. When the anchorage length increases to a certain value, the load no longer increases. The anchorage length increases from 30 mm (2.5 d) to 120 mm (10 d), and the ultimate bonding strength decreases by 22.89%. A three-stage bonding stress slip relationship was used to establish a bonding slip constitutive model for GFRP reinforced coal gangue concrete, laying a theoretical foundation for the study of bonding and anchoring performance of such components.