Study On Thermal Expansion Coefficient Of Concrete Under Extreme Temperature

With the development of global economy and the progress of science and technology,the demand of infrastructure construction under extreme temperature is growing.As the most widely used building material,concrete is the first choice of building structural materials under extreme temperature.The thermal performance of concrete in extreme temperature environment will change significantly compared with that in normal temperature environment.As a parameter to characterize the thermal deformation performance,the change of the thermal expansion coefficient of concrete in extreme temperature environment needs to be analyzed and studied.Considering that it is difficult to test the thermal expansion coefficient of concrete under extreme temperature,based on the subproject of "Experimental Research on reinforced concrete components under extreme temperature" jointly carried out with China Huanqiu contracting & Engineering Corporation and Wuhan University,the test method and calculation theory research of the thermal expansion coefficient of concrete are carried out,so as to carry out the temperature measurement of concrete structure under extreme temperature in the later stage The state analysis of force changing with temperature provides reference and reference.The specific research contents are as follows:(1)The test methods of temperature strain and stress strain in extreme temperature environment were studied.The traditional quartz differential method and half bridge connection temperature compensation test method are improved.The in-situ compensation test method is proposed to effectively separate the material physical deformation caused by temperature and the deformation caused by load under the coupling effect of temperature and load,so as to provide the basis for the test and measurement of the thermal expansion coefficient and mechanical property parameters of the material under the extreme temperature.(2)Carry out mortar,stone and steel bar test pieces and temperature related part of the performance parameters test.The temperature thermal strain of mortar,stone and steel bar in the ultra-low temperature and high temperature environment is measured,and the change rule of thermal expansion coefficient of mortar,stone and steel bar with temperature in the range of-165 ? ~ 500 ? is obtained.The mechanical properties of mortar and stone Cube Specimens under the coupling of temperature and force were measured.The variation of elastic modulus and Poisson's ratio of mortar and stone with temperature in the range of-165 ? ~ 500 ? was obtained.(3)The numerical analysis model of linear expansion coefficient of concrete is studied.The concrete is regarded as a two-phase material composed of mortar and coarse aggregate.On the basis of obtaining the mechanical parameters of mortar and stone specimens under normal temperature environment,the concrete numerical simulation model is established and the mechanical parameters of concrete are predicted.The predicted values are compared with the test values of concrete specimens to verifythe reliability of the concrete simulation model.According to the test results of mechanical parameters of materials and thermal expansion coefficient under extreme temperature,two methods of numerical simulation and theoretical formula calculation are used to simulate the change rule model of thermal expansion coefficient of concrete with temperature.