ABSTRACT
If some flaws with different contents and forms exist in different positions of concrete or other construction, thermal conductivity and specific heat or other properties will be changed partly. When heat transmirted,the infrared radiating power will be affected and the temperature distribution will be changed remarkably. So difference in temperature will appear in the thermal image. The injured features of freeze-thaw concrete structure are that loose layer appears gradually from surface to interior, a large number of microcrack spread inside it, more seriously the surface layer will peel off with or even without finger touching. The present structure of surface layer is essentially made of air and micro-hydration products through weak binding power and the heat transmittion will be blocked by air . In the end the surface temperature of these positions will be raised and thermal spot will appear in infrared thermal image.The temperature range of thermal spot is conversely corresponding to the injured degree and range of this position, so structural evaluation can be made by analyse of infrared thermal image.
