Abstract
When fire-damaged Reinforced Concrete buildings are investigated, it is very important to evaluate maximum temperatures of concrete and steel in main structural parts and to diagnose the degree of damage to each member. This paper describes a new method to evaluate maximum temperatures during fire, utilizing the characteristic of an admixture responsive to thermal variations. Even if the quantity of admixture in concrete is small, its absorbance of ultraviolet rays can be measured with high accuracy because of its sensitivity. Concrete test samples were heated to every 100°C from normal temperature up to 600°C, and the absorption curves were obtained at each temperature. The relations between temperatures and absorbances were derived from the measured absorption curves, and showed almost linear relations. Therefore, it was found that maximum temperatures in concrete could be evaluated from absorbance measurements.
The validity of this evaluation method was verified by fire tests of a column and a floor. In the results, the evaluated values agreed with the ones measured by thermocouples. Moreover, the method was applied to various actual fires. In the results, it was found that the method could be applied to the fires and that the maximum temperatures in the concrete damaged by fire were accurately obtained by the method.
