Research On Dynamic Mechanical Properties Of Reactive Powder Concrete After High Temperature

Reactive Powder Concrete(RPC)is a type of high-performance concrete without coarse aggregates,which has ultra-high strength,high toughness and high durability.In recent years,the research on RPC has mostly focused on normal temperature and its static mechanical properties,while on the high temperature and dynamic mechanical properties are relatively less.The service environment of concrete in modern engineering is more and more complex,which is likely to be affected by external loads such as fire,high temperature,and impact.In order to study the dynamic mechanical properties of RPC in complex environment,this thesis mainly carries out the following research through SHPB(Split Hopkinson pressure bar)test:(1)Construction of RPC dynamic constitutive model after high temperature.The effects of temperature,strain rate and fiber content on the dynamic stress-strain curve and failure morphology of RPC were investigated experimentally.The dynamic stress-strain curves of RPC under various influencing factors were obtained,and the dynamic constitutive model of RPC after high temperature was established based on the obtained dynamic stress-strain curves fitting.(2)Analysis of dynamic mechanical properties of RPC after high temperature.The dynamic mechanical properties of RPC after high temperature were measured from five aspects: dynamic compressive strength,peak strain,dynamic strength growth factor,toughness,and dynamic elastic modulus.The influence of temperature,strain rate,fiber volume content and other factors on the dynamic mechanical index of RPC was obtained.(3)Numerical simulation of RPC impact compression after high temperature.The SHPB test model of reactive powder concrete is established by LS-DYNA finite element software using HJC(Holmquist-Johnson-Cook)constitutive model.By adjusting the parameters of HJC constitutive model,the simulation results of RPC under the impact of different strain rates were obtained.The accuracy of the simulation model was verified by comparing with the experimental data.In conclusion,in this thesis,through the SHPB test,RPC with different high temperatures,different strain rates and different fiber contents were systematically studied by means of test and simulation,and the dynamic constitutive model of RPC and its dynamic mechanical indexes were obtained.The results of this thesis provide a theoretical basis and experimental basis for the design of RPC as an anti-high temperature and impact-resistant structure in engineering,and have certain guiding significance for the popularization and promotion of RPC.