Theoretical Analysis And Experimental Research On Tensile Performance Of Reinforced Reactive Powder Concrete

Reactive Powder Concrete(RPC) is a new generation concrete material,compared with conventional concrete,it possesses excellent properties such as ultra-high strength,high toughness and high durability etc.The excellent characteristics especially for high compressive strength and high tensile toughness make RPC a revolutionary application prospect in civil engineering field.For RPC is often reinforced by steel bars in application,it has great theoretical and practical signigicance to carry out the experimental research of RPC and reinforced RPC on their tensile behavior.Based on the national natural science foundation of China,the uniaxial tensile tests of RPC and reinforced RPC are developed,and the investigated results can be listed as follows:(1) Based on the reference review and experimental results,a self-designed uniaxial tensile test equipment is developed.RPC as well as reinforced RPC uniaxial tensile tests are completed.In order to solve the stress concentration problem,a dumbbell-shaped specimen combined with variable-thickness copper sheet is used in the test and gains satisfied effect.The innovative test method developed by author is suitable for reinforced concrete in direct tension;(2) The test reveals that the complete uniaxal tensile stress-strain curve of RPC (V_f =1%,2%) can be obtained through Universal Testing Machine without any stiffness-strengthen devices.The test also shows that the tensile failure mode of RPC changed from brittleness to ductility before and after steel fiber added.As for reinforced RPC,it is found that all specimens exhibit well restricted-fissure performance when strengthed with steel bar.There are two types failure mode of reinforced RPC in uniaxial tensile test,that is,single-slit failure when np＜0.20 and multiple-slit failure when np≥0.20;(3) In view of the effect of restrained shrinkage on tensile test results,a restrained shrinkage modified model of reinforced RPC is developed.Based on this model, tensile stress-strain curves eliminated shrinkage effection of reinforced RPC are abtained.Comparative analysis shows that after strengthed by steel bar,the descending segment of RPC tensile stress-strain curve is mainly influenced,and reinforcement ratio parameter n,o is the main influential factor;(4) According to analytical results,a theoretial trilinear constitutive model of reinforced RPC tensile stress-strain curve is constructed.For the sake of convenience,a practical simplified tensile stress-strain model of reinforced RPC is also presented. These two theoretical models can provide theoretical basis to the whole process nonlinear analysis of reinforced RPC structures;(5) Based on microstructure of RPC and fracture mechanics theory,the tensile mechanism of RPC and reinforced RPC are studied.The reasons of high toughness of RPC and well restricted-fissure performance of reinforced RPC are interpreted.