2023 Volume 77 Issue 1 Pages 112-119
The mechanism of hysteresis generation in pore structure analysis using thermoporometry is discussed. The pore size distribution during the melting process was similar to that obtained by the mercury intrusion method, in which the sample was dried in the pretreatment process. This indicates that the hardened cement paste is dried during the freezing process in thermoporometry, resulting in changes in the pore structure. This well explains the previously pointed out change in pore structure due to treatment before measurement, indicating the necessity of measuring the pore structure considering the environment to which the hardened cement paste is exposed. The analysis of the measured data with varying water content confirmed the existence of two types of C-S-H gels in the hardened cement paste, LD C-S-H （outer C-S-H） and HD C-S-H （inner C-S-H）, as indicated by Jennings et al. and Goto et al. Furthermore, it is found that LD C-S-H has an ink-bottle pore structure with an entrance pore corresponding to a 2nm gel pore that is frozen by homogeneous nucleation.
