Experimental Study And Analyse On Bond Behaviors Between Reinforcing Bars And ECC

Engineered cementitious composites,referred to as ECC,is widely used in the constructions,which has super high tensile strength,toughness and durability so that it can effectively solve the problems caused by brittleness of concrete.Fiber Reinforced Polymer/Plastics,referred to as FRP,commonly including CFRP bars,GFRP bars and BFRP bars,etc.Compared with the traditional steel bars,FRP bars have more excellent corrosion resistance,higher strength and lower density,especially,it play an more and more crucial role in solving the corrosion of the traditional steels,there is a wide application prospect in various fields of civil engineering.In this paper,the reinforcing bars mainly include all kinds of steel bars and FRP bars.Based on the summary of the existing results,combining the excellent performance of FRP bars and ECC,this paper explored the bondimg behaviors of steel bars-ECC and FRP bars-ECC respectively,the study on the bonding properties of reinforcing bars-ECC can provide guidance on its popularization and application in practice.The unidirectional loading test is used to analyze the bond-slip relationship between reinforcing bar and ECC under various influencing factors such as ECC strength,type and diameter of reinforcing bars,external constraint,etc.The specific research contents are as follows:1)Introduced the mix proportion and preparation process of the ECC.From two aspects of tensile and compression performance,the conventional mechanical properties of ECC with different strength grades are tested,and the difference between them and the mechanical properties of the traditional concrete is compared.2)Studied the bonding properties of steel bars and ECC.A total of 30 unidirectional loading specimens are designed for 10 working conditions and taking a comprehensive consideration about several factors such as ECC strength,steel diameter and hoop constraint,the multi-factor coupling on the steel bars-ECC performances such as bond strength,peak load slippage,hoop strain and bond-slip relationship curve are explored,the failure mode and crack development of the specimens are observed and analyzed statistically.3)Studied the bonding properties of CFRP bars-ECC and GFRP bars-ECC.By 33 unidirectional loading specimens under 10 working conditions,comprehensive consideration ECC strength,type and diameter of FRP bars,hoop constraint,studied their influence on bonding strength of FRP bars-ECC,peak load slippage and the bond-slip relationship curve,the crack development and failure modes of the specimens had been carried on the summary.4)On the basis of the existing bond-slip constitutive relations,the bond-slip relationship curves of reinforcing bars-ECC,CFRP bars-ECC and GFRP bars-ECC are analyzed by using the experimental data,and the fitting effects of each model are compared and evaluated.