To detect the spalling of the deteriorated concrete surface, active infrared thermography method using the Xenon-Arc Lamp heating system has already been developed. To simplify the heating device system and widen applicable condition, reduced heat emission power was applied to the inspection test on the existing reinforced concrete viaduct. According to the test result, spalling can be detected with the reduced heat emission power, but distinction between the part without deterioration and the spalled part came to be rather ambiguous. To solve the latter problem, a new infrared image processing method focused on the changing trend of the temperature distribution was developed and its availability was proved.
