Analysis of the UWVE specimens can now be formulated in the context of the CM for SWVE specimens. For the specimens exposed to 90 % RH, the primary difference is the loss of freezable water within the pores.
The water loss was most evident in the specimens exposed to 90 % RH at a young age. For all values of w/c, the UWVE specimens at 6 h and 12 h never exhibited a freezing peak at -30 ºC. Moreover, those 6 h and 12 h specimens that formed a peak at -45 ºC eventually lost all the water from those pores. The loss of water from the -45 ºC peak indicates that, upon consumption of all the available free water, the chemical driving force for hydration is sufficient to extract water from the reservoirs surrounded by LD C-S-H pores.
The 3 d and the 7 d data for the 0.3 w/c and the 0.4 w/c pastes were, in general, consistent with the data from the SWVE specimens. Because the -30 ºC peak had disappeared prior to 3 d for SWVE 0.3 w/c pastes, the paste was sufficiently able to retain moisture to continue hydrating at a rate equal to that of a sealed specimen. As has been observed from chemical shrinkage measurements, as impermeable as the SWVE 3 d 0.3 w/c paste is, it is still able to absorb moisture in a 100 % RH environment. This accounts for the difference in the hydration rate between the 3 d and the 7 d 0.3 w/c pastes.
The 3 d 0.4 w/c paste, having only just formed the -30 ºC peak, was still able to lose water to the environment (the rate of hydration was slower than that for a sealed specimen) because a sufficient volume of capillary pores were not surrounded by inter-LD pores. The 7 d 0.4 w/c paste (being under similar conditions, with respect to the -30 ºC peak, as the 3 d 0.3 w/c paste) continued to hydrate at a rate equal to a sealed specimen, which is identical to a SWVE specimen at this w/c value.
The 3 d and 7 d 0.5 w/c paste data highlight different aspects of cement hydration. For both cases, the -30 ºC peak has not formed at the time of exposure. Based on previous arguments, the capillary pores are sufficiently percolated to lose a large quantity of evaporable water. Interestingly, both the 3 d and the 7 d 0.5 w/c pastes continued hydrating at a measurable rate. Although some capillary water was probably lost from both systems, it appears as though hydration continued by consuming water trapped in the LD C-S-H pores that freeze at -45 ºC (6 h and 12 h DSC data demonstrate that hydration can remove water from these pores). In fact, the -45 ºC peak height for both the 3 d and the 7 d systems appears to decrease. The fact that the 7 d system is able to hydrate at the same rate as a SWVE system is not altogether surprising because higher w/c pastes contain greater volumes of water in the LD C-S-H pores that freeze at -45 ºC [33].