Prediction of Thermal Decomposition of Hardened Cement Paste

Abstract

When exposed to elevated temperatures, various constituents in hardened cement paste will undergo decomposition, resulting in thermal damage of concrete. To better understand the thermal damage mechanism, it is essential to investigate the whole decomposition process of hardened cement paste. Based on the kinetic and stoichiometric analysis, a numerical method is presented in this paper for predicting the thermal decomposition of hardened cement paste. In this method, the initial volume fractions of various constituents in hardened cement paste are expressed as a function of the water-to-cement ratio, degree of hydration, and the chemical composition of cement. By analyzing the kinetics of decomposition, the volume fraction evolution of each constituent is then formulated in terms of the heating rate and temperature. When silica fume is added, the pozzolanic reaction is also considered. Finally, the validity of the proposed numerical method is verified with three sets of experimental data collected from the literature. The effect of the heating rate on the thermal decomposition of hardened cement paste is evaluated in a quantitative manner.