Experimental Study On Flexural Behavior Of BFRP Reinforced Recycled Aggregate Concrete Beams With Recycled Brick Aggregates

Before the 1990 s,most of the buildings were brick and concrete structures in China.With the gradual demolition of these buildings,a large amount of complex construction waste has been generated,including discarded bricks,discarded concrete,mortar blocks,etc.Considering the limitations of the current economic and technological level,it is impossible to adopt a large number of classification and recycling models based on ingredients.Therefore,the mixed recycled aggregate prepared by using this type of construction waste has complex composition and poor performance stability.The recycled aggregate concrete（RAC）mixed with recycled aggregates has poor crack resistance and strong water absorption,which is easy to induce corrosion of steel bars,which seriously affects the safety of components or structures.Basalt fiber reinforced polymer bar（BFRP bar）is a new type of composite bar composed of resin and basalt fiber,which has excellent tensile properties and anticorrosion properties.By combining BFRP bars and recycled aggregate concrete containing recycled brick aggregates（RAC-RBA）into a BFRP reinforcement recycled concrete structure,it is not only conducive to the efficient recycling of construction waste,but also to solve the problem of steel corrosion.The promotion and use of this new material component is of great significance,but there are few studies in this direction at present.In this paper,mixed recycled coarse aggregates were used to make recycled concrete,and BFRP bars were used to completely replace the steel bars of the beams.The flexural performance of BFRP bars RAC-RBA beams under symmetrical loading under two-point concentrated loads was studied.The main contents and results of the completed work were as follows:（1）Research on the material properties of RAC-RBA,BFRP bars and steel bars.The physical and mechanical properties of various material components of RAC-RBA were measured,and the effect of the content of recycled aggregate on the strength of RAC-RBA was studied through the mechanical properties test of its cubes and cylinders.Through the tensile performance test of BFRP bars and steel bars,the tensile strength,elastic modulus and other performance parameters of the BFRP bars and steel bars under tension in this test were obtained.（2）Experimental research on the flexural performance of BFRP reinforcement RAC-RBA beams under two-point symmetric concentrated static load.Through the bending failure test of 8 beams,including 1 BFRP reinforced NAC beam,6 BFRP reinforced RAC-RBA beams and 1 reinforced RCA-RBA beam,stuied the types of reinforcement（steel reinforcement,BFRP reinforcement）,reinforcement ratio（0.40%,0.60%,0.86%,1.07%）,BFRP reforcement dismeter（10mm,16mm）and the amount of recycled aggregate（0,50%,100%）and other factors.The failure form of the test beam,Characteristic loads,overall working performance of the section,strain deformation,deflection deformation,crack development and ductility were analyzed.（3）Theoretical research on the flexural performance of BFRP reinforcement RACRBA beams.Three calculation methods were selected from the ACI 440.1R-15,CSA.S806-12 and GB50608-2020 to calculate the theoretical values of characteristic load,deflection at midspan under service load and ultimate load,and maximum crack width under service load and ultimate load of BFRP reinforcement RAC-RBA beams.The differences between the experimental values and the theoretical values were compared.The proposed calculation formula for the cracking load of the BFRP reinforcement RAC-RBA beam and the recommended formulas for the ultimate load,deflection and maximum crack width were proposed.