Research On The Properties Of Concrete And Practical Identification Methods After The Building Fire

With the development of society and the level of urbanization raise,the frequency of all types of building fires is increasing rapidly,and constitutes a serious threat to people's life and property safety.At present concrete is the main load-bearing material that is universally used in the all types of industrial and civil buildings,transportation,bridges,water conservancy and a variety of special structures.Concrete is made of cement played a role of adhesion,skeleton role of stone and sand mixed water,which is a hot inert polyphase and compound material.It has good durability,fire resistance and integrity.However,if the concrete is under the high temperature condition for a long time,or suffers sudden heat shocks,will cause complex changes of the concrete performance indicators.When the performance of concrete after different high temperature is studied,the different temperature is the main considered factor;in addition,the different cooling method,fire time,concrete strength and other factors are usually ignored.In order to accurately analyze the residual bearing capacity of the concrete structure after fire,it is very important to consider the relationship between the concrete mechanical properties and temperature,fire time,cooling method etc.factors.It will provide supporting evidence for the assessment,identification,restoration and reinforcement of fired concrete structures.The stress mechanical properties of a plurality strength grade concrete material after high-temperature,fire time and cooling-method are tested analyzed.Meanwhile,according to the experimental results,a practical identification methods for concrete structures after high temperature is established.The specific work of this article is summarized as follows:(1)Based on the high temperature test of different strength grade concrete material,the results show that with the fire temperature and time that the concrete material suffers continues,the apparent color of the concrete produced the change from shallow to deep,addition,specimens also appear more and more serious phenomenon such as lacking of edges and shedding of skin.At the same time,We also obtain the surface physical properties of the concrete material after fire,such as surface color,appearance damage,mass loss,etc.with the changing-rule about the concrete after fire temperature and time.The fire temperature can be approximately calculated from these physical changes,which will provide support for the detection,identification,reinforcement about the fire.(2)Concrete materials are to conduct fire tests according to the international standard ISO-834 temperature rise curve.Choosing the different time by the fire is to analysis the temperature field of concrete specimens.(3)Experimental researches were made on the variation of multiple strength grade concrete mechanical behavior with different cooling method,fire time,based on the given different strength grade of concrete specimens and the way to rise,to constant and to cool in the article,we can use the experimental data to fit the relational expression between compressive strength and fire temperature and time.(4)The trial also studied the effects of different cooling treatments on the compressive strength of concrete specimens after fire.The internal reasons and law of changes of concrete cooled by watering are analyzed.(5)Based on the experimental researches and summarizing the domestic and foreign research achievements of the testing,identify and the evaluation about the fire,a feasible and practical identification methods for concrete structures after high temperature is established.Overall,the study on the performance of concrete after high temperature exposure is conducted,and the results may provide some references for engineering practice and future experimental research.