The predicted and measured compressive strength developments are provided in Figures 11 and 12, for cements 135 and 136, respectively. The prefactors used to calibrate to the 3 d measured results were 110.7 MPa and 105.4 MPa for cements 135 and 136, respectively. In the past, calibrating the model to the 3 d measured strength using Powers' gel-space ratio  has provided excellent model predictions of 7 d and 28 d measured strengths for CCRL cements 115 and 116  and for CCRL cement 133 . For both cements 135 and 136, however, calibration to the 3 d values resulted in the model overpredicting the 28 d strength. Conversely, calibrating the model values to the 7 d measured strength (using prefactors of 96.5 MPa and 100.3 MPa for cements 135 and 136, respectively) results in model-predicted 28 d values which are within one standard deviation of the measured mean response. The 28 d predictions are still higher than the measured values, in agreement with the observed differences in the predicted and measured 28 d heats of hydration provided in Tables 3 and 4. Further research is needed to assess the reliability of the model-predicted strengths for a wider variety of cement types. With this in mind, CCRL cements will continue to be evaluated in this manner as they are released for proficiency analysis in the future.