The LOI non-evaporable water content measurements were carried out following a procedure described elsewhere [12]. Non-evaporable water content was determined as the relative mass loss between 105 ºC and 1000 ºC, corrected for the LOI of the dry cement powder itself. To convert the non-evaporable water content measurements to estimated degrees of hydration, α, it was necessary to determine the non-evaporable water content for a fully hydrated sample. Based on the compositions of the two plain portland cements listed in Table 1, values of 0.24 g H2O / g cement and 0.234 g H2O / g cement were determined for cements T-1H and T-1D, respectively. The degree of hydration was then determined as the ratio of the measured non-evaporable water content per gram of cement to the amount at full hydration.