Figure 1 shows a schematic view of the structure of the VCCTL. This is a computer-based "virtual laboratory" whose goal is to reduce the number of physical concrete tests, whether for quality assurance or for expediting the research and development process. Many of the models developed at NIST over the last 10 years are at the stage where their predictions are quantitative and accurate. Many standard tests can be replaced by computer models right now, and many more in the future, so that, for example, a cement company that develops a new cement will be able to immediately predict many facets of the performance of concrete made from this cement. Models available now can handle the effects of: (1) different kinds of curing, which involves cement particle size distribution and composition, mineral admixtures, and temperature and moisture conditions; and (2) aggregates, which include the particle size distribution (as given by a sieve analysis), volume fraction, degree of saturation, and shape. These models can now, or soon will be able to, predict: degree of hydration, chemical shrinkage, heat release, diffusivity, set point, strength development, elastic properties, and slump (yield stress and viscosity). Databases are also becoming available for using the cement hydration model for various cements, which are an important component of the VCCTL (see http://ciks.cbt.nist.gov/phpct/database.html).
The earlier CIKS for predicting chloride diffusivity of concrete has been integrated into the VCCTL. The VCCTL consists of a WWW-based menu-driven interface (front end) that controls the execution of the underlying models and returns plots of the quantitative results back to the user. Version 1.0 of the VCCTL should be available by the time this article appears (see http://vcctl.cbt.nist.gov). A consortium of industrial companies is being formed to do the computational and experimental research needed to improve and extend the VCCTL in order to make it more powerful and usable.
Figure 1: Schematic overview of the structure of the Virtual Cement and Concrete Testing Laboratory. Italics indicate a capacity that is planned, but not currently available.