In a fire event, it is well known that the strength of a concrete material significantly decreases, and in some cases, concrete building structures can collapse. This is mainly due to the chemical decomposition of hydration products of cement paste at elevated temperatures. This study is to provide the crucial information about how to determine the fire damaged temperatures and the damage level of cement paste. Samples were exposed to 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 oC, respectively. After that, all heated samples were carefully collected and analyzed, in order to further investigate the variation of their thermal properties, which, in turn, can reveal a clue of the fire-damaged temperatures. X-ray diffraction, scanning electron microscope, accelerated carbonation tests were conducted to find the decomposition of hydration, collapse of pore structure, and deterioration of durability at a specific-damaged temperature. Test results showed that the higher the temperature, the more is the amounts of chemical decomposition, and the higher is the volume of pores in the cement paste samples. In conclusion, this study proposes a 'standard directory' that contains the information on the chemical variation of hydration products in cement paste at different elevated temperatures.

Keywords: Fire damaged temperature, Damage level of cement paste, Carbonation tests.