Study On The Mechanical Properties Of CFRP-Concrete Bonding Interface On Hygrothermal Environment

Having a light weight,high strength,corrosion resistance,fatigue resistance,etc.features,carbon fiber reinforced polymer(CFRP)are widely used in the field of civil engineering reinforcement.In the study of CFRP reinforced concrete members,the basis of two different materials working together is that the adhesive interface performances well.Because the reinforcement members are mostly long-term exposed,the mechanical properties of the bonding interface would be affected by the ambient temperature and humidity.So it is necessary to study the mechanical properties of CFRP-Concrete bonding interface under hyperthermal and humid environment.This paper was supported by the Construction Technology Project of Ministry of Transport(Grant No.2015318814190).The key technology research on durability of the girder bridge after bonded reinforcement under coupling loadand in hydrothermal environment.In the paper,the author make use of double shear test of concrete samples and three-point bending test of CFRP reinforced concrete beam to study the mechanical properties of CFRP-Concrete under hyperthermal and humid environment.Mainly aspects and conclusions are as follows:(1)Through double shear tests of concrete,we carried out 25 o C/95%RH ?25o C/85%RH?60o C/95%RH?60o C/85%RH and 5d?10d?15d in totall 52 groups of CFRP-Concrete bonding interface mechanical property research under five kinds of experimental conditions after three different cracking time.Double shear failure modes show that the influence of the humidity on bonding interface is very large at a high temperature.And hyperthermal and humid environment has a very large negative impact on the CFRP-Concrete reinforcement interfacial bonding capacity.What's more,ultimate loads of group B(25o C)is higher than the control group at room environment(8o C).While it 2decreased significantly when it was 60 o C.A small humidity difference doesn't work much on the ultimate load at a low temperature.while at hyperthermal environment,it could significantly decrease the ultimate load even a small humidity increase.(2)Three-point bending reinforced concrete beam test shows,60 o C/95%RH environment have negative effects on the performance of CFRP and concrete interfacial bond property: after 5d ? 10 d and 15 d of function time,testing beams' ultimate loads fell 1.44%,3.39% and 6.63% respectively in contrast with the control group at room environment.(3)According to the strain obtained from the tests,the author adopt bilinear equations which consider the characteristics of the material itself?temperature effects?humidity effects and two factors coupling effects.Then the the CFRP-Concrete interface bonding-slipping constitutive model is set which includes effects of temperature and humidity.It analyze the mathematical methods under hyperthermal and humid environment and mathematical expression is get based on the experimental results.the analyze method provide a reference for the further research on the CFRP-Concrete interfacial bond property under a hyperthermal and humid coupling environment.