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Mortar Strength Development

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 [8] has provided excellent model predictions of 7 d and 28 d measured strengths for CCRL cements 115 and 116 [3] and for CCRL cement 133 [4]. 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.


  
Figure 11: Experimentally measured (circles) and model-predicted compressive strength development for ASTM C109 mortar cubes prepared from CCRL cement 135. Solid line indicates model calibration to the 3 d measured strength while dotted line indicates calibration to the 7 d measured value. Crosses indicate ± one standard deviation from the mean, as determined in the CCRL testing program.
\begin{figure}
\special{psfile=strplot135.ps hoffset=-20 voffset=35 vscale=65 hscale=65 
angle=-90} \vspace{11.0cm} \vspace{0.10in}\end{figure}


  
Figure 12: Experimentally measured (circles) and model-predicted compressive strength development for ASTM C109 mortar cubes prepared from CCRL cement 136. Solid line indicates model calibration to the 3 d measured strength while dotted line indicates calibration to the 7 d measured value. Crosses indicate ± one standard deviation from the mean, as determined in the CCRL testing program.
\begin{figure}
\special{psfile=strplot136b.ps hoffset=-20 voffset=35 vscale=65 hscale=65 
angle=-90} \vspace{11.0cm} \vspace{0.10in}\end{figure}


Next: Summary Up: CEMHYD3D Results Previous: Heat of Hydration