Evalution Of The Performance Of Different Types Of Concrete After High Temperature By The Ultrasonic Method

There were great difficulties to evaluate the performance of the concrete after fire,the reason was the variety types of the concrete which due to the variety of factors inthe modern building structure. With the broad application of the ultrasonic detectiontechnology in concrete, the results were different when tested by different parameters.Therefore, it was necessary to select the appropriate parameters to ensure the accuracyof test results.Currently, the study of the performance of the concrete after high temperature,which was applied the method of ultrasonic, was focused primarily on one type ofparameters or one type of concrete. Based on the study of existing theories,experimental studies had been carried out on the ordinary portland concrete, highstrength concrete and mixed with polypropylene fibers reinforced high strengthconcrete, under different high temperatures up to200℃,400℃,600℃and800℃,along with the tests of the compressive strength and the flexural strength. Meanwhile,combined with ultrasonic detection technology, the research of the performance of thedifferent types of concrete after high temperature had been carried out, which utilizethe relative velocity, the relative amplitude and the damage degree.The results showed that, the form of the attenuation of the velocity and amplitude,which was measured in the three types of concrete after high temperature, werenonlinear attenuation. The fitting results of heating temperature, loss rate ofcompressive strength and loss rate of flexural strength on relative wave velocity,relative amplitude and damage degree of these three types of concretes were analyzed.As can be seen from the results, the fitting result of the linear function was the worst,however, the results both of the quadratic polynomial and exponential function werethe best and little difference between them. The difference of the performance afterhigh temperature between the concretes were analyzed based on the method ofultrasonic, the fitting result in R2up to0.993and the average relative error is less than5%. Therefore, the performance of the concrete after high temperature, which wereimpact by the different types of concrete, can be ignored. The evaluation method using damage degree or relative wave velocity led to identity results. At the same time, therelative velocity and the degree of damage is universal which to different types ofconcrete. In comparison to the relative velocity and the degree of damage, the fittingresults in R2minimum to0.708and the average relative error reached22.33%. Thencethe results did not have identity, not as the relative amplitudes did the evaluationparameters of concrete after high temperature.