The non-evaporable water content (wn) of each crucible sample was determined as the mass loss between 105 ºC and 1000 ºC divided by the mass of the ignited sample, corrected for the LOI of the unhydrated cement powder, determined in a separate LOI measurement. Previously, the expanded uncertainty in the calculated wn has been estimated to be 0.001 g/g cement, assuming a coverage factor of 2.18 The values of wn were converted to estimated degrees of hydration based on the phase composition of the cement (Table 1) and published coefficients for the non-evaporable water contents of the various cement clinker phases. 19 Based on a propagation of error analysis, the estimated uncertainty in the calculated degree of hydration is 0.004.