Experimental Study On Flexural Behavior Of FRP-reinforced Crumb Rubber Concrete Beams

Fiber reinforced polymer bars(FRP bars)are light weight with high tensile strength and good corrosion resistance.They could be used in reinforced concrete structures instead of steel bars and solve the durability issue associated with steel bar corrosion.However,since FRP bars are linear elastic material with a relatively lower elastic modulus,FRP reinforced concrete beams might have much wider cracks and higher midspan deflections under the serviceability limit state,with a brittle failure mode.Crumb rubber concrete(CRC)is a new type of environmental-friendly concrete material,which is made up of Portland cement concrete added with rubber particles,with good crack resistance and deformability.The combination of FRP bars and CRC is aimed at making full use of the good deformability of CRC and the high tensile strength of FRP bars,thus increasing the crack resistance and improving the brittle failure mode of FRP reinforced concrete beams,which can further promote the application and development of FRP reinforced concrete structures.In this paper,the mechanical properties of FRP bars and CRC with equivalentstrength design were investigated,six simply-supported FRP reinforced concrete beams and CRC beams were designed,and their flexural behavior under two-point monotonic symmetrical loading were investigated.Finite element analysis software ABAQUS was used to simulate the flexural behavior of FRP reinforced CRC beams,and parametric studies were conducted to understand the influence of rubber content,reinforcement ratio,concrete strength grade and cross-section height on the flexural behavior of FRP reinforced CRC beams.Design recommendations of FRP reinforced CRC beams were proposed,based on FEA results and theoretical calculation.The results show that:(1)Through optimization of mix design and pretreatment of rubber particles,crumb rubber concrete can be obtained with equivalent strength as ordinary concrete.When CRC with equivalent-strength design is used in FRP reinforced concrete beams,FRP reinforced CRC beams can reach higher ultimate bending capacity,with higher crack resistance and deformability,and enhanced ductility,as compared with FRP reinforced ordinary concrete beams.(2)The flexural behavior of FRP reinforced CRC beams can be analyzed relatively precisely by ABAQUS.Increasing rubber content can increase the cracking moment up to 28%,increase the bending capacity up to 10%,and improve beam ductility.When the reinforcement ratio increases,the flexural stiffness and ultimate bending capacity of the beams could be increased obviously,with little influence on the cracking moment,while the reinforcement ratio cannot be increased without limitation.The concrete strength grade has much influence on the cracking moment but little influence on the final limit state.When the cross section height increases,it is easier to satisfy the requirement on midspan deflection.(3)Strain distribution on the cross section of FRP reinforced CRC beams basically obeys the assumption of plane section.Code formulas for the cracking moment,midspan deflection,crack width and ductility index of FRP reinforced concrete beams are evaluated in regards to their applicability to FRP reinforced CRC beams.Formulas are proposed for the ultimate bending capacity of FRP reinforced CRC beams and design recommendations are given.