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A unique, multi-phase, random, complex, and composite material, concrete provides both strength and impermeability to engineered structures. Unlike most construction materials, the properties of concrete continue to develop over time and in place−assisting processing and fabrication. Testing and quality assurance, however, become more complicated. For instance, having to wait 28 days to ensure performance compliance is a unique, but not necessarily an attractive, feature of concrete. Computer models today attempt to reduce the length of this waiting period through the prediction of cement and concrete properties by means of virtual testing. Based upon a detailed characterization of starting materials, such models predict a variety of properties of both fresh and hardening concrete. Successful prediction of properties with virtual testing will result in tremendous time and cost savings to the cement and concrete industry, and will play an important role in enabling the use of performance specifications. Virtual testing will also support the capability to rapidly perform a large number of "what-if" type computations to explore and optimize new material systems.
The successful prediction of properties through virtual testing is the goal of the National Institute of Standards and Technology (NIST)/Industry Virtual Cement and Concrete Testing Laboratory (VCCTL) consortium. Its members currently include two NIST laboratories (Building and Fire Research and Information Technology) and nine industrial members: Holcim (US) Inc., International Center for Aggregates Research, Portland Cement Association, National Ready Mixed Concrete Association, Sika Technology AG, Verein Deutscher Zementwerke eV, W.R. Grace & Co., Degussa/Master Builder Technologies, and Association Technique de l'Industrie des Liants Hydrauliques. A report on the progress of this consortium's work follows, along with a general overview of what virtual testing of cement and concrete actually is and what it aims to accomplish.