Experimental And Theoretic Research On Using Infrared Thermal Mapping To Probe Into Concrete Defect

In the fields of international and domestic civil engineering, there is an urgent need to research on some important subjects such as to thoroughly assess the constructed concrete bridges, tall buildings, viaducts and dams, to solve the problems of low efficiency, high cost and insecurity caused by traditional check methods in seeking the potential danger of the concrete - constructions, and to quickly carry out loss less exploration in whether the concrete crack and the bare hole will remove from the outside walls of tall buildings. The fulfillment of these subjects will bring enormous social and economical benefit.However, the complication in checking conditions, and the uneven, porous and unstable anisotropic composite materials for the reinforced concrete of modern buildings, which has complex structure and disperse quality, make the infrared loss less checking technique not widespread in civil engineering as in other industrial fields.In this paper, the experiments and theories of using infrared thermal mapping to probe into the concrete defect are given as the main research contents of the "Inspection Method for Evaluating Decaying Concrete Using Thermal Infrared Remote Sensing System" which is subsidized by National Natural Science Foundation. Based on relative results, by combining the finite element imitation computation with experiments together, this paper explores the principles and methods in the loss less checking of concrete defect.The paper mainly deals with the following aspects:1. According to thermal radiation laws and thermal conduction functions of the concrete, the principles and methods by using the infrared thermal mapping technology to carry out loss less inspection for concrete are expounded.2. According to thermal conduction formulation and thermal radiation boundary terms, the formula to calculate the depth of the internal defect in concrete is theoretically put forward and the available range and terms of the formula are established. In addition, the formula for cut-off error is also given.3. The techniques for the finite element thermal analysis are applied to imitate the thermal conduction in concrete at all kinds of defect sizes and object sizes. Furthermore, the formula to calculate the defect depth is also worked out by using concrete surface temperature.4. Similarity theories are applied in the experiment of solid thermal conduction model. As a result, the prototype test difficult to be realized in laboratory is successfully carried out through some similarity principles. By studying the defect depth and size in various types and standards, the variation curve of the defect size is designed in this paper, and the problem on how to use the curve to seek the defect depth and size is solved as well.5. The figure temperature field is formed by analyzing the concrete surface temperature field taken by infrared thermal mapping instrument. The experiment result is also compared with the finite element analytic result so as to search a more accurate measuring method.Finally, by summarizing all the research work, some unsolved problems concerning this subject are proposed.