Research On Relationships Of Temperature History And Micro-structure Evolution Mechanism Of High-strength Concrete

In recent years,the rapid development of the national economy,more and more high-rise buildings,housing density increasing,the high-rise building with high strength concrete.Compared with ordinary concrete,high stre ngth concrete has a serious deterioration of high temperature performance,mainly because of low permeability of high strength concrete,easily lead to burst failure,so that the structure of refractory time is greatly reduced.So it is necessary to study the variation of the microstructure and mechanical properties of high strength concrete under different temperature.In view of the domestic and foreign research status and existing problems on the microstructure evolution mechanism and mechanical properties of high strength concrete,in this paper,by comprehensive means of scanning electron microscope,X ray diffraction,mercury porosimeter,ultrasonic detectorand Micro hardness tester,the physical and chemical changes of the high strength concrete after different high temperature process and the microstructure changes caused by the process are analyzed,and the relationship between the temperature history and the microstructure evolution of high strength concrete is established.Specific work was as follows:The temperature field distribution of concrete was measured by thermocouple,and combined with the finite element simulation analysis method ABAQ USto study the distribution of the temperature field of the test block.Through the temperature of high strength concrete compressive strength test,and further establish temperature history and high strength concrete micro structural changes and mechanical properties of the relation model,forming of concrete temperature process,microstructure and mechanical properties of the relationship between the scientific method.The study of high strength concrete properties under high temperature,in different temperature history,shows different characteristics of concrete block changes,mainly in color,size and number of cracks and loose degree etc..Then the temperature history and the mechanical properties of concrete are studied.Compared with ordinary concrete,the mechanical property loss of high strength concrete under high temperature is larger than that of ordinary concrete.By using the finite element software ABAQUS,the standard cube the section temperature field distribution were analyzed by numerical simulation,and compared with the results measured by thethermocouple,the results fit wel.Study on the mechanism of the temperature history and microstructure evolution of high strength concrete.Through scanning electron microscopy images of cement slurry,in the aggregate and cement paste interface transition zone hydration calcium silicate gel,needle shaped ettringite(AFT)and hexagonal plate shape calcium(Ca(OH)2)and cement hydrate morphology,status,quantity and pore and crack,observation of X-ray diffraction(XRD)profiles in the crystallization phase,qualitative analysis microstructure characteristics;By measuring the parameters of sound time,amplitude and frequency,the porosity,pore size and micro hardness were measured,and the relationship between micro parameters and temperature history was obtained.By using statistical software SPSS,correlation analysis of temperature history and various microstructural parameters respectively,on the basis of the good correlation,the mathematical model of the relationship between the temperature and the temperature history and the residual strength is established.And based on the qualitative analysis,the relationship model of microstructure parameters temperature history and residual strength was established.The model can not only scientifically and quantitatively describe materials in high temperature process under the action of the microstructural features and the relationship between damage,and accurate quantitative microstructural parameters and high temperature process and mechanical properties of the relationship.