Experimental Study On The Bond Durability Of BFRP Bars Embedded In Concrete

Fiber-reinforced polymer（FRP,Fiber Reinforced Polymer）bars are considered to be ideal substitutes for reinforcement in marine environments due to their excellent mechanical properties and good corrosion resistance.In recent decades,basalt fiber-reinforced composite（BFRP,Basalt-FRP）ribs,as a new type of composite ribs,have received widespread attention from scholars because of their environmental protection and high cost performance.However,due to its short development and application time,the long-term performance data and degradation mechanism of the BFRP bar-concrete bonding interface are currently poorly controlled,which restricts the application and promotion of the BFRP bars concrete structure to a certain extent.In this paper,an experimental study on the durability of the BFRP bar-concrete interface bond durability was carried out,and the improvement method of the fly ash mineral admixture was explored in view of the potential alkali aggregate reaction potential of the BFRP bar.The main research contents and results of this article are as follows:（1）First,the long-term performance degradation of BFRP bars in the accelerated corrosion environment of the laboratory was studied.The room temperature（25°C）,40°C and 55°C were used to simulate the seawater and alkaline solution immersion environment.The results show that water molecules penetrate into the BFRP bars through the interface between the fiber and the resin matrix,which causes the resin matrix to swell and the performance of the bars decreases.Under simulated seawater environment,Clˉreacts with Fe²⁺in basalt fiber;under alkali solution environment,the ester bond in the resin matrix is??broken,and Si O₂in basalt fiber reacts with alkali,which accelerates the performance degradation of BFRP bar,Due to the high content of Si O₂in basalt fibers,the performance of BFRP bars deteriorated more in alkaline solution environment.（2）The long-term performance degradation of the BFRP rebar-concrete interface adhesion performance under accelerated laboratory conditions was studied.The immersion environment used room temperature（25°C）,40°C,and 55°C to simulate seawater and alkaline solutions.The results show that the bond strength of the BFRP bar-concrete interface is mainly determined by the shear strength of the BFRP bar interlayer,and the failure mode is the rib peeling failure of the surface layer of the BFRP bars.（3）The influence mechanism of the addition of fly ash on the long-term performance of the BFRP reinforcement-concrete interface is studied.The study found that the bond strength of the BFRP bar-concrete interface with fly ash increased by an average of 10.0%.The main reason is that the fly ash has the effect of refining the pores in the concrete,which reduces the penetration rate of the corrosion solution to the bonding interface during the immersion,and the fly ash inhibits the alkali aggregate reaction of the active silica in the BFRP bars.（4）Based on the Arrhenius theory,the bonding performance of the BFRP bar-concrete interface is predicted.In the natural marine immersion service environment,the retention rate of the bond strength of the BFRP bar-concrete interface is about 36.9%after 30 years.