Study On Flexural Behavior Of Reinforced Concrete Beams Strengthened With BFRP Grid And PCM

In recent years,basalt fiber reinforced polymer（BFRP）grid-polymer cement mortar（PCM）has been used in the reinforcement of concrete structures,this reinforcement system is called B-FRCM（BFRP-Fabric-Reinforced Cementitious Matrix）.This reinforcement technology has the advantages of high temperature resistance,low price,adaptability to low temperature environment or wet surface,and compatibility with concrete substrate.The defect is that the bond between cement-based binder and existing concrete interface is relatively poor,which affects the bending reinforcement effect of beams.In this paper,an experimental study is carried out on the reinforcement of reinforced concrete beams with BFRP grid-PCM.The main research contents and conclusions are as follows:（1）Single shear tensile test of externally attached concrete specimens of B-FRCM reinforcement system.When the interface was treated with propionic emulsion interface agent or combined with impregnation adhesive,the failure mode was changed from debonding to fiber rupture,and the corresponding ultimate tensile force was 157.95% and244.32% higher than that of the contrast specimens,respectively.The effective bond length theory is also applicable to B-FRCM reinforcement system.The classical interfacial stress theory formula is also applicable to the B-FRCM reinforcement system,and the theoretical calculation results are in good agreement with the experimental results.（2）5 reinforced concrete beams for bending reinforcement,and four point bending test.The cracking load and ultimate load of the reinforced beam increase with the increase of the number of BFRP layers,and the ultimate load of the five-layer BFRP grid increases by37.09% compared with the reference beam.After using BF unidirectional cloth to anchor the end of the reinforced beam,not only can the end of the reinforcement system be effectively constrained to prevent it from debonding,but also can increase the shear bearing capacity of the component,so that the brittle failure caused by debonding or shearing can be transformed into ductile failure.（3）Through theoretical calculation,the ultimate load,peeling load and cracking load are compared with the test results of B-FRCM reinforcement system.Because it is impossible for multilayer fiber bundles to rupture at the same time,the difference of the flexural capacity between the experimental and theoretical values is less than 13%.Compared with the reference beam,it can be seen that the B-FRCM reinforcement system can greatly increase the cracking load of the strengthened beam,up to 63.27%.