| High performance concrete(HPC)has been used in many important projects,especially in Bridges,high-rise buildings,rail transit and other projects,showing its unique superiority,and at the same time,it has also produced remarkable benefits in the aspects of safe use period,economic rationality,adaptability of environmental conditions and so on.In order to promote the development of engineering construction in cold areas,electric induced hardening was adopted to study the synergistic effect of coarse aggregate and cement mortar on the mechanical properties of CFRP and the interaction of coarse aggregate and carbon fiber on the resistivity and mechanical properties of CFRP under negative temperature environment.Then the dosage of coarse aggregate,carbon fiber and cement mortar is optimized to ensure the project quality and reduce the project cost.In this paper,firstly,the influence of coarse aggregate content on the stability of the conductive network constructed by carbon fiber is studied,and the suitable mixture ratio of carbon fiber high performance concrete containing coarse aggregate is optimized.Secondly,the influence of electric induced hardening on the micro-structure and static mechanical properties of carbon fiber high performance concrete was studied.Based on the heat transfer theory,the average thermal conductivity of concrete in the whole curing process from plastic state to solid state was calculated by using the modeling software COMSOL.Based on the validity of the simulation,the corresponding load power required by electric induced hardening was simulated under the external environment of-30℃～-60℃.Finally,the dynamic mechanical properties of electric induced hardening specimens were studied.The main research contents and results are as follows:Firstly,the mix proportion and preparation technology of carbon fiber in high performance concrete was studied,and good preparation was determined by the test,in guaranteeing concrete has smaller resistivity and higher mechanical performance under the premise of through a series of experiments,the influence factors such as mixing process,coarse aggregate content,carbon fiber content and the analysis of the interaction of the two.The optimal combination of carbon fiber content of 0.5vol% and coarse aggregate content of 20% was determined,and then the optimal mix ratio of electric induced hardening carbon fiber concrete was determined.The load power of electric induced hardening experiment was determined to be 30 W by contrast test.Secondly,the mechanical properties of electric induced hardening specimens,standard curing specimens and steam curing specimens under-20℃ environment were studied.It was found that electric induced hardening specimens could accelerate the formation of early strength of cement mortar and prevent the specimens from freezing.At the same time,the micro-structure and hydration products of the electric induced hardening specimens at-20℃ were studied.The scanning electron microscope analysis,TG analysis and XRD diffraction analysis showed that the electric induced hardening concrete specimens had a relatively dense micro-structure and a relatively high degree of hydration.The average thermal conductivity of concrete in the whole process of electric induced hardening is 0.72W/(m·K),which is simulated by COMSOL software.Based on the validity of the external temperature simulation at-20℃,the load power of electric induced hardening at-30℃～-60℃ is predicted,and the validity of the simulation is verified by the electric induced hardening test at-30℃.Finally,SHPB test technology was used to carry out impact tests on specimens under different curing regimes.Compared with other curing regimes,the stress growth of specimens as well as the variation law of DIF value and strain rate of specimens were studied,and CEB 2010 empirical formula was modified. |
