Using of phenolphthalein solutions in fire-damaged concrete was investigated, leading to the following conclusions.
1. Traditionally, colorless areas appeared after spraying waterless phenolphthalein solution on fire-affected concrete, thought to be above 500°C. However, these areas were actually dry regions exposed to temperatures over 150°C.
2. Even in aged concrete structure undergoing carbonation and drying over time, it was determined that the use of a waterless PP solution enables the identification of areas experiencing temperatures above 150°C.
3. By using water-containing PP solution, the thermal decomposition range of CaCO3 where was heated above 600°C can be identified.
