Experimental investigation on bond behavior of CFRP-concrete interface with end anchorage in hygrothermal environments

Externally bonded reinforcement (EBR) of reinforced concrete (RC) structures with fiber reinforced polymer (FRP) is unable to meet the requirements of the engineering. Because premature debonding failure limits the usage scenario of the EBR method, which cannot fully utilize the high tensile performance of FRP. More and more studies focus on the improvement of the EBR method by extra anchors on the FRP-concrete interface to improve its ultimate strength. Considering the influence of environmental conditions on the FRP-concrete interface with anchorage, the application of extra anchorage under hygrothermal environments has to be investigated. The paper optimizes the existing end mechanical anchorage to avoid damage to carbon fiber reinforced polymer (CFRP) and concrete substrate. The compressive pressure exerted on the CFRP laminate can be controlled by adjusting the torque on the end anchorage. A series of end-anchoted doublelag shear tests under different hygrothermal conditions were carried out for invesitgating the bond behavior of CFRP-concrete interface. The test results showed that the load increment of the ultimate strength of the CFRP-concrete interface decreased with the increase in temperature and relative humidity. Correspondingly, friction surfaces due to the compression provided by end anchorage changed from concrete-concrete interface to the concrete-adhesive or adhesive-CFRP interfaces. The relationship between friction coefficient and temperature and relative humidity was built. The shear stress and slip distribution curves were calculated from the strain distribution functions fitted from the strain data measured by DIC. Fracture energy for the CFRP-concrete bond was estimated, and the bond-slip relationship for the hygrothermal conditions was constructed.