Experimental Study On Durability Of The Interface Between CFL And Concrete Under Wet-thermal Condition

The outstanding characteristics of fiber reinforced polymer (FRP) are their high strength,good corrosion resistance, fatigue resistance, etc. which make FRP reinforced concretestructures be widely applied in the field of civil engineering. The reinforce effect and failuremechanism of FRP reinforced structures have the close relationship with FRP-concreteinterface, Therefore, it is necessary to study on the durability of FRP-concrete interface underwet-hot environment. The study here focuses on the bond-slip mechanism of CFL-concreteinterface under static load; based on the carbon fiber laminate (CFL) invented by our researchgroup, and to explore the interface durability of CFL-concrete in wet-hot environment byexperimental studies. The Main contents and conclusions as followed:(1) Considered the environmental characteristics of the sub-tropical regions, to propose asuitable temperature and humidity aging environment and accelerated simulation. Based onthe double shear test, the effect on the bonding properties of the interface between the CFLand concrete in wet-hot environment was investigated. The results showed that the wet-hotenvironment had a negative impact on the interfacial bonding properties between the CFLand concrete, with the temperature of heat aging, the specimen ultimate load, the initial peelload, maximum strain and peak shear stress has a different the degree of reduction.(2) The damage mechanism, transmission of interfacial stress and evolution ofinterfacial slip are discussed here by the results of static experiments of CFL-concreteinterface and the analysis of damage process and failure modes. The bond-slip constitutiverelationship of CFL-concrete interface based on Popovics model, hyperbolic model, andbilinear model are introduced, and thereafter the formula for characteristic parameters ofcurves are also given here. The wet-hot aging and at room temperature specimens werecompared with analysis effect of the wet-hot environment on the CFL-concrete interfacialbond constitutive relation.(3) By the analysis of the bonding mechanism of interface, the failure mechanism forbond-slip of CFL-concrete interface is described here from the perspective of damage. Thedamage variables and threshold are given for describing the damage process of interface anddamage-slip models for bond strengthen and bonded stiffness are put forward based on the bond-slip constitutive relations of CFL-concrete interface.