Effect of elevated temperatures on chemical properties, microstructure and carbonation of cement paste

Abstract

In a fire event, it is well known that the strength of a concrete material significantly decreases, and in some cases, concretebuilding structures can collapse. This is mainly due to the chemical decomposition of hydration products of cement paste atelevated temperatures. This study is to provide the crucial information about how to determine the fire damaged temperaturesand 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 variationof their thermal properties, which, in turn, can reveal a clue of the fire-damaged temperatures. X-ray diffraction, scanningelectron microscope, accelerated carbonation tests were conducted to find the decomposition of hydration, collapse of porestructure, and deterioration of durability at a specific-damaged temperature. Test results showed that the higher thetemperature, the more is the amounts of chemical decomposition, and the higher is the volume of pores in the cement pastesamples. In conclusion, this study proposes a ‘standard directory’ that contains the information on the chemical variation ofhydration products in cement paste at different elevated temperatures.