Experimental Study On Mechanical Properties Of Different Types Of Concrete At High Temperature

With the increase of urban housing intensity,the wide application of new materials,and the universal use of gas and electrical automation,the probability of building fire is greatly improved.After the fire,not only the strength of concrete material is reduced,but also the ability of concrete to resist erosion decreases rapidly.Therefore,it is necessary to carry out experimental research on the durability and durability of concrete after high temperature.The main work of this article is as follows:(1)summarized the current research status and research problems of different strength concrete at home and abroad after high temperature.(2)based on the high temperature test,the rule of concrete appearance and mass loss with temperature is studied.With the increase of temperature,the order of apparent color change of the specimen is bluish grey to brown grey to white to red.When the temperature is 300-400 C,there are a few fine cracks on the surface of the specimen,and the number of cracks increases gradually;when the temperature is 500 C,there are many cracks on the surface of the specimen.A large number of wide cracks appear on the surface of the specimen when the temperature is 700 C-800 C.With the increase of temperature,the mass loss rate of concrete with different strength increases gradually,and the strength grade and quality loss have little influence.(3)the change of compressive strength of concrete block with temperature,fiber content and cooling mode under different temperatures,different intensities and different cooling methods is analyzed and studied.The test results show that with the increase of temperature,the compressive strength of the concrete specimen decreases gradually after the high temperature,and the downward trend increases with the increase of temperature,and the content of different rigid fibers has a certain influence on the compressive strength of the concrete specimen after high temperature.(4)the general methods of building fire risk assessment,including qualitative analysis,semi quantitative analysis and quantitative analysis,are briefly introduced.Based on the test,a preliminary discussion is made on the nondestructive testing,evaluation and identification of the concrete after fire.