Because most of the models used in the VCCTL software are rooted in - and operate upon - the details of cement particle microstructure, an accurate and comprehensive knowledge of the starting materials is crucial to the predictive ability of the simulations. Ideally, the most comprehensive model would start from atomic details, and predict macroscopic behavior based solely upon the locations and types of atoms that are present and the environmental conditions. Such a model is far beyond present capabilities. This makes it crucial to experimentally supply many details that the models need so that they may accurately predict macroscopic behavior. This kind of information is generally in the nature of material characterization. In general, the required analyses are nothing more exotic than those that previously have been applied to cements. However, they must be performed more systematically and thoroughly than they have been in the past. Once this is accomplished, the full predictive power of the models can be utilized.
Prior research using the models has revealed the importance of pinpointing for cement the value of the following variables: 1) volume and mass fractions of each cement phase in the material, including mineral admixtures and gypsum; 2) surface-area fractions of each component of the cement phases, as a measure of how phases are distributed within particles; 3) the particle size distribution of each major cement phase, because particle size is probably the main variable controlling reactivity; and 4) the degree of flocculation or agglomeration among cement particles.
A major thrust of the VCCTL consortium has been to create a "cement database" that catalogs the salient microstructure features of a wide range of cements that are needed as input for the VCCTL models. We have begun to work with ASTM, via committee C01 on Cement, to build these needed measurements into the standards so that this kind of information is routinely available, thus making the models more easily and widely usable.