Virtual testing is a fashionable name, given the ubiquity of "virtual" anything and everything around us today. But, what does it really mean in reference to cement and concrete materials? In condensed-matter physics, properties of simple materials are measured at a fundamental level. These measurements are then compared to quantitative predictions from condensed-matter theory that is based on valid mathematical principles applied to well-characterized atomic and molecular arrangements. In materials science, however, more complex materials are studied. These include random composites, biological materials, and concrete. For these and others like them, it is not possible to undertake analytical calculations. Thus, the field of computational materials science has been developed with the necessary condensed-matter mathematics solved on computer. Consequently, the virtual testing of cement and concrete is just computational materials science applied to cement and concrete.An ideal model for concrete would be one that starts from the known chemical composition of the material. Beginning with the correct proportioning and arrangement of atoms, the modeling effort would build up the needed molecules, then the nanostructure and microstructure, and would eventually predict properties at the macroscale level. This idealized model, however, is still a long way off even with modern-day computers.
Science-based virtual models that do exist need high-quality data as input that emanate from careful characterization of the materials. The models can predict physical properties of interest to actual materials users, but are based on fundamental parameters and not on empirical testing. For example, measuring the Blaine fineness as a characterization of a cement powder does not provide useful data for a model. On the other hand, careful measurement of the cement particle size distribution (PSD) by, for example, laser diffraction does give particle-level information vital to the successful modeling of how the cement hydrates and develops microstructure.
A functional VCCTL actually increases the need for physical testing and standards. Firstly, property predictions for a model can only be as good as the characterization of the starting materials. Thus, standardized methods for preparing and analyzing such materials will be critical. Secondly, measurements of fundamental properties are needed to validate the predictions. The VCCTL procedures will not eliminate standard tests, but will reduce their number. At the same time, the procedures will drive such testing away from empiricism to a firm basis in materials science.