The legacy FORTRAN version of the elasticity model has been rewritten in C and directly incorporated within the VCCTL software system. It can take as input the cement paste microstructure as given by the CEMHYD3D model, and operate on it to compute the cement paste elastic moduli. However, the elastic moduli output is only as good as the phase elastic moduli input. NIST researchers have combed the geological literature to find the available cement/cement paste mineral elastic moduli data. There also have been some recent data reported in the cement literature on cement clinker minerals and on C-S-H. The VCCTL consortium is committed to measure any other individual phase elastic moduli that are needed. Agreement between model and experiment is quite reasonable for some later-age, Type 1 specimens that were measured elastically by a member of the consortium. Figure 10.3.2 shows this 28-d and 56-d data (saturated curing), plotted against w/c ratio, for both experimental and model results. The agreement is usually within 5%. Other later-age experimental results for cements of different finenesses also have been predicted well by the model; at equivalent degrees of hydration, fineness does not seem to have a significant effect on elastic moduli.
Figure 10.3.2. Comparison of elastic moduli predictions to experimental data, vs. w/c ratio, for 28-d and 56-d specimens. At each w/c ratio, the upper point is the 56-d value and the lower point is the 28-d value.