| Fiber reinforced polymer（FRP）has the advantages of light weight,high strength and strong chloride corrosion resistance.It is expected to replace steel bars to improve the long-term durability of concrete structures in marine engineering and other corrosive environments.However,the alkali resistance of B/GFRP reinforcement is poor,and corrosion will occur in alkaline environment,resulting in strength degradation.The commonly used Portland cement（OPC）concrete contains hydrated product calcium hydroxide（Ca（OH）2）with high alkalinity.The composite of B/GFRP reinforcement and OPC concrete will reduce the bond strength between reinforcement and matrix due to the deterioration of FRP reinforcement due to alkali corrosion,which will have an adverse impact on the structural durability.Therefore,the application of B/GFRP reinforcement is restricted.In view of this,this study uses low alkali corrosion-resistant cement（slag sulphoaluminate cement（G·SAC）and high belite sulphoaluminate cement（HB·SAC））to replace OPC.Different from OPC system,the hydration product of this cement is mainly ettringite（AFt）without Ca（OH）2.Concrete is prepared based on low alkali corrosion-resistant cement,which has high sulfate resistance.It is compounded with FRP to form B/GFRP reinforcement-low alkali corrosion-resistant cement concrete,which solves the problem that FRP reinforcement is vulnerable to alkali environment corrosion in OPC concrete,and further ensures the bonding performance between FRP reinforcement and concrete.The purpose of this paper is to study the time-varying law of B/GFRP reinforcement low alkali corrosion resistant cement concrete interface bonding performance,establish an analysis model of B/GFRP reinforcement low alkali corrosion resistant cement concrete interface bonding strength,and clarify the evolution mechanism of B/GFRP reinforcement neutral energy and bonding strength in low alkali cement（G·SAC and HB·SAC）concrete matrix.The research results will provide new materials,new technologies and new theories for improving the durability of concrete structures.The main research contents include:（1）Through pore solution piezometric titration test,the pore solution of OPC,G·SAC and HB·SAC paste specimens cured with fresh water and sea water was taken to study the deterioration of B/GFRP reinforcement in different pore solutions;（2）Through pull-out test,the time-varying law of interfacial bonding properties of B/GFRP bar OPC concrete,B/GFRP bar G·SAC concrete and B/GFRP bar HB·SAC concrete in seawater and fresh water environment is studied;（3）Based on the long-term performance prediction method of FRP bars,the bond strength durability prediction model is established.The results show that:（1）the p H of G·SAC and HB·SAC matrix cured with fresh water is lower than OPC;The p H of cement matrix decreases due to seawater curing,but the alkalinity of OPC cured with the same seawater is still higher than that of low alkali cement（G·SAC and HB·SAC）;（2）In the fresh water environment,with the increase of curing time,the interfacial bond strength between B/GFRP reinforcement G·SAC concrete and B/GFRP reinforcement HB·SAC concrete gradually increased,while the bond strength between B/GFRP reinforcement and OPC concrete matrix gradually decreased;（3）In seawater environment,the bond strength of B/GFRP bar-HB·SAC concrete and B/GFRP bar-G·SAC concrete increased more significantly than that in freshwater environment. |
