Experiment Study Of The Bond Performance Between CFRP And Concrete In NSM Reinforcement Under Freeze-thaw Cycling

In recent years, carbon fiber reinforced plastics(CFRP) reinforced concrete structure has been rapid development, compared with the Surface mounted CFRP strengthening method, the Near Surface Mounted CFRP strengthening technology has some advantages of high material utilization and durable performance, it has the very good application prospect in the field of engineering reinforcement. However, CFRP and concrete interface bonding failure mechanism has not been very good explanation, especially under the action of freeze-thaw cyclings is rarely reported, so it is necessary to research on it.Therefore, this article has carried on the 33 of CFRP and concrete block single shear test, inspection of test parameters include: freezing and thaw cyclings, concrete properties, bond length of CFRP plate and tank wall thickness, buried depth and so on. And the main contents include: ultimate load, failure pattern, stick-slip curve and bonding failure mechanism of specimens NSM CFRP and concrete. The results show that:1.With the increase number of freeze-thaw cyclings, C30 concrete strength gradually reduce, and C60 concrete strength increased,but the growth rate was gradually reduced, it indicates that the C60 concrete has secondary curing effect under the freeze-thaw cyclings.2.With the increase number of freezing-thaw cyclings, the specimen's bond failure modes gradually translated from CFRP strip tensile failure to the resin and concrete interface,and last to the interface of CFRP- resin stripping damage, And the ultimate load are reduced grasually.on the one hand, it showed that freezing and thaw cyclings obviously effect the bonding specimens on its bearing capacity, on the other hand, it also showed the damage of interface rein and concrete was worse than the tinterface CFRP and rein which was caused by freezing-thaw cyclings. And improve the strength of concrete can significantly improve the freezing-thawing resisting performance of interface rein and concrete.3.The interface's stripping was significant increased of the specimen with 40 mm distance from groove edge to the prism edge under the freezing and thaw environment, the ultimate load is also significantly reduced. The degradation was significantly higher than specimen with 70 mm. and it showed that the minimum distance from groove edge to the prism edges should be greater than 40 mm under the reeze-thaw environment.in addition,compare with the 300 mm bond length, The CFRP plate utilization rate is high with the bond length 250 mm although it under the freezing and thaw environment, but the bond performance was significantly reduced when the bond length was selected 450mm(4.5mmCFRP).4.The change of CFRP strip embedment depth has not serious impact on specimen's interface peoformance when it under the room environment. The CFRP plate with three sides embedded was not significant suffered by the freezing and thawing erosion,but some of the leakage of specimen has a great influence on the interfacial bonding performance.5. The linear fitting of ultimate load under the action of the freezing-thaw cyclings,established NSM CFRP and concrete ultimate load reduction equations of theoretical formula under the freezing-thaw cyclings,and it was improved a certain reference value.