| Epoxy resin is generally used as the interface structural adhesive in the carbon fiber cloth reinforced concrete system.However,due to the strong temperature sensitivity of this type of colloid,the mechanical properties of the colloid are rapidly deteriorated near the glass transition temperature(50 ° C ～ 80 ° C),and the interface It is prone to bond failure and damage,so it is not suitable for high temperature environment reinforcement.Inorganic cementitious material,as the adhesive for the reinforced interface of CFRP cloth,has the advantages of good high temperature stability,which can solve the problem of sticking CFRP cloth in high temperature environment.Magnesium oxychloride cement(MOC)is an inorganic cementitious material with light-burned magnesium oxide and magnesium chloride as the main raw materials.It has the advantages of fast hardening and high strength of the interface structural adhesive.Therefore,this study carried out the high temperature performance test of the MOC interface adhesive and the high temperature The bond performance test of concrete reinforced specimens pasted with MOC after action,the research results have important theoretical guiding significance for promoting the application of CFRP reinforcement technology in high temperature environment.The main research contents and conclusions are as follows:(1)Research on the high temperature resistance of MOC structural adhesive.The high-temperature degradation mechanism of MOC colloid properties was analyzed through the related mechanical properties test of MOC after high temperature,combined with XRD and other test methods.The results show that the mechanical properties of MOC decrease with the increase of temperature.When the temperature is lower than 300 °C,the MOC is in the water loss stage.Due to the evaporation of free water in the MOC system and the decomposition of crystallization water in the 518 phase crystal,the mechanical properties of the colloid decrease but the deterioration rate is slow.When the temperature exceeds 300°C,the MOC enters the weight loss stage,and the 518 phase crystal begins to decompose in large quantities and finally generates Mg O and HCl,and the mechanical properties of the colloid deteriorate significantly.(2)Evolution law of bonding properties of CFRP-MOC-concrete interface after high temperature.Through the in-plane shear test,the evolution law of bonding performance indicators such as interface failure mode,interface bearing capacity and stress-strain value was analyzed.the result shows:(1)With the increase of temperature,the failure of the bonding interface will change from the failure of the adhesive layer and the CFRP cloth to the failure of the adhesion of the adhesive layer and the concrete.(2)With the increase of temperature,the bonding performance indicators such as interfacial bearing capacity,maximum stress and strain value decrease,especially when the temperature exceeds 300℃,the decreasing speed is accelerated;(3)The increase of CFRP cloth width and concrete strength will increase the bonding performance indicators such as interface bearing capacity,maximum stress and strain value;(4)The initial interface stiffness and fracture energy decreased with the increase of temperature,and increased with the increase of CFRP cloth width and concrete strength.(3)The effective bond length of the interface will decrease with the increase of temperature and concrete strength,but it is basically not affected by the width of CFRP.The bond length calculation model was further based on the classical model,and the temperature influence coefficient was introduced to establish the CFRP-MOC-concrete interface bearing capacity calculation model after high temperature damage. |
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