Experimental Study On Temperature Field Of Concrete Structure Under Freezing And Thawing Environment

In the cold area, concrete structures are subjected to the long-term sustained damage of freeze-thaw cycles and seriously exposed to the serviceability and safety problems. The freeze-thaw damage of concrete is mainly caused by the freezing of pore water under negative temperature, so the research on temperature field of concrete structures under freezing and thawing environment has great significance for the guidance of the project practice on the frost resistance durability design and assessment.By adopting the structural member test and theoretical analysis method, the dissertation systematically studied the temperature field of concrete structure in the process of freeze-thaw cycles and the detailed work is as follows:(1) With the accomplishment of the freeze-thaw cycle test of concrete wall and the adjoint concrete specimens, this research had realized the temperature monitoring of 28 testing point in three directions in the process of 40 freeze-thaw cycles that each of the cycles is 24 hours long and analyzed the change of temperature field of concrete member. The results indicates: Concrete members are in cyclical changes in the internal temperature of each poi nt, and micro moves of environment temperature lead to few effect on the temperature field; In the same direction, the peak temperature of each testing point decays quickly and the attenuation is largest within the range of 0 ~ 25 mm in depth; The delay ti me of peak temperature is gradually increased along with depth growth and obviously prolongs after more than 100 mm.(2) Using the theory of heat transfer and the concept of temperature wave, the research analyzed attenuation law of the peak of temperature field of concrete member and came up with a practical calculating method for the peak value of temperature field in an arbitrary point; The research also explored the infect intensity and depth of the temperature field led by freeze-thaw cycles.(3) The research had carried out the test of concrete strength after f reezing and thawing damage and made contrast analysis of the concrete strength loss before and after freezing and thawing testing and studied the declination regularity of the internal strength of concrete stucture after freezing and thawing cycles. The research also divided the influence area of temperature field. The result shows: The temperature field led by freezing and thawing cycles has huge impact on the surface layer of concrete structure, causing great damage and losing much strength. But it has little effect on the internal part of the concrete structure with few damage and little strength reduction. The influence rule of freezing and thawing temperature field on concrete strength further supplements and perfects the temperature field impact model which is proposed in this dissertation.