Small pieces of the hydrated cement pastes were also used in the LTC experiments. Sample mass was typically between 30 mg and 90 mg. For each LTC experiment, one small piece of the relevant cement paste was surface dried and placed in a small open stainless steel pan. The pan with the sample, along with an empty reference pan of similar mass to the empty sample pan, was placed in the calorimeter cell. Using a protocol developed previously, 10 a freezing scan was conducted between 5 ºC and −55 ºC at a scan rate of −0.5 ºC/min. For temperatures between −100 ºC and 500 ºC, the equipment manufacturer has specified a constant calorimetric sensitivity of ± 2.5 % and a root-mean-square baseline noise of 1.5 µW. The peaks observed in a plot of heat flow (normalized to the mass of the sample) versus temperature correspond to water freezing in pores with various size entryways (pore necks). The smaller the pore entryway, the more the freezing peak is depressed. Thus, the presence of, absence of, or change in peaks can be used to infer information concerning the characteristic sizes of the "percolated" (connected) water-filled pores in the microstructure of the hydrating cement pastes. One advantage of LTC over mercury intrusion porosimetry, and other techniques for assessing pore size and connectivity, is that specimens are evaluated without any drying that might damage the pore structure. Of course, the LTC technique can only assess the size and connectivity of water-filled pores. For non-saturated curing conditions, it is assumed that "empty" pores formed due to self-desiccation will not contain any freezable water and thus will not show up on the LTC scans.