Experimental Study On Anchoring Performance Of RC Reactive Powder Concrete And Steel Bars

Reactive Powder Concrete(RPC)is an ultra-high-performance fiber-reinforced concrete with advantages such as ultra-high strength,high toughness,high durability,and good environmental protection.This kind of concrete will be used in the field of civil engineering.Great ecological and economic benefits.In engineering,reactive powder concrete often participates in the structure's stress in the form of reinforcing members,so the study of the bonding performance between steel bars and reactive powder concrete has become an urgent problem.So far,domestic and foreign scholars have achieved some results on the related research on the bonding performance between steel bars and reactive powder concrete.Based on previous studies,this paper studies the bond performance between steel bars and RC reactive powder concrete(reactive powder concrete for on-site pouring)through a central pullout test.The compressive strength of concrete is the water-cement ratio(0.16,0.19,0.22),the volume of steel fiber(0,0.5%,1.0%,1.5%,2.0%,2.5%),and the diameter of the reinforcing steel(14mm,18mm,22mm).The bonding lengths of steel bars and active powder concrete(45mm,72mm,99mm)are used as parameters.66 active powder concrete center-pull out test pieces and 2 steel bar-reinforced strain gauges with center-pull out test pieces are designed and manufactured.After the pull-out test of all the specimens,the bonding performance between deformed steel bars and RC reactive powder concrete under the influence of multiple factors is analyzed,and a corresponding anchor length calculation method is proposed.This method can be used for reinforced reactive powder concrete.Application provides design basis.The research content and main work of the thesis include the following aspects:(1)Determine the mix ratio and curing system of reactive powder concrete;perform compressive strength test on 22 sets of cube test pieces cured under the same conditions as the test specimen pulled out from the center,and obtain the mechanical performance index of RC reactive powder concrete;The tensile test obtained the physical properties of the steel bar.(2)Based on the pull-out test of 22 groups of center pull-out specimens,and the failure mode of center pull-out specimens,the characteristics of bond stress slip curve(?-s curve)are analyzed,and the characteristic values of bond anchorage strength r0,?s,?u,?r,bond anchorage slip characteristic values Ss,Su,Sr are obtained.(3)Analysis of the influence of various factors on the characteristic value of the anchoring and anchoring of reactive powder concrete.The research results show that the bonding strength of steel bars and reactive powder concrete increases with the increase of the compressive strength of the concrete;as the amount of steel fibers increases,?u and ?r shows an increasing trend;as the diameter of the reinforcing bar increases,?0 decreases first and then increases,and ?u and ?r decrease;as the bonding length of the reinforcing bar increases,?0 and ?r increase,and ?u decreases.(4)According to the characteristics of the bond stress-slip curve,the experimental data were fitted and analyzed to obtain the empirical formula for calculating the bond anchorage characteristic value of RC-type reactive powder concrete steel bars,and the average bond stress-slip constitutive relationship was established.(5)The center pull-out test of the specimen with a strain gauge inside the steel bar was carried out.Based on the measured strain of the steel bar,the bond stress distribution law within the bond length range was analyzed,and the bond position function was established based on the law and measured data;combined with the average The bond stress-slip constitutive model and the bond position function are used to obtain a model that can reflect the bond stress-slip constitutive relationship in the bond length range.(6)Based on the above formula for calculating the bond strength between active powder concrete and steel bars,the center point method was used to calculate the statistical value of the anchorage length of the steel bars in the active powder concrete.The length calculation formula proposes a correction factor to provide a reference for engineering design.