Investigation of the Freezing/Melting Process of Unsaturated Cement Paste by Low Temperature Calorimetry

Low temperature calorimetry (LTC) is usually applied to characterize the porosity of cement-based materials with a total water saturated state. By recording the heat flow of the sample at different testing temperatures, the ice content in the freezing and the melting process can be analyzed. In order to investigate the state of the water during the freezing/melting process of unsaturated porous materials, different from previous study, cement pastes of different moisture content are utilized and tested by LTC test. It is found that the nucleation temperature is independent of the degree of saturation in the range of 87%–100%, while the influence of the degree of saturation on the melting process is significant. For the melting process, the trough temperature increases with the decreasing degree of saturation, and water movement takes place in unsaturated samples during a freezing/melting cycle.