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Next: The Virtual Cement and Concrete Testing Laboratory
E.J. Garboczi, D.P. Bentz, and G.J. Frohnsdorff
National Institute of Standards and Technology
Building Materials Division
100 Bureau Drive, Stop 8621
Gaithersburg, Maryland 20899-8621
Within the Building and Fire Research Laboratory at the National Institute of Standards and Technology (NIST), the Partnership for High Performance Concrete* Technology (PHPCT, see http://ciks.cbt.nist.gov/phpct/) is working to develop the materials science knowledge necessary for making high performance concrete (HPC) a usable, well-understood, and durable material, thus enabling the reliable application of high-performance concrete in buildings and the civil infrastructure. This work involves the combination of experimental and computational materials science research, which is needed to address the complex nature of concrete. The delivery of the output of this research is focussed on developing computer integrated knowledge systems (CIKS), which are a synergistic combination of databases, models, and computational tools. This paper describes the current status of such systems presently available for use by concrete technologists.
The NIST research that is going into the computational systems and tools to be described in this article is divided into six themes within the PHPCT.
(1) Processing of HPC, which is addressing methods for selecting and proportioning ingredients, determining the rheological properties, and selecting the mixing, placing, and consolidation procedures and the curing conditions to assure a product of the desired performance and uniformity.
(2) Characterization of Concrete and Concrete Materials, which aims at providing techniques needed for characterizing the composition and properties of concrete materials, and the composition, structure, and uniformity of an HPC produced by any process or from any source.
(3) Performance Prediction, which is developing a suite of models for simulating and predicting transport and other durability-related properties of HPC.
(4) Structural Performance of High-Strength HPC in a Fire, which is developing methods for predicting the effects of fire on the performance of high-strength HPC.
(5) Structural Performance, which is providing knowledge needed to allow for the most rational use of high-strength concrete and take account of its performance.
(6) Economics of HPC, which is developing models for calculating the life-cycle costs of HPC in infrastructure applications, beginning with bridge decks and then proceeding to other structures.
Clearly, NIST research alone cannot generate all the knowledge that is needed to go into the CIKS systems. The remainder of the knowledge that is needed must be generated from partners from industry and government, who have joined with NIST in the PHPCT. Partners include the Portland Cement Association, Holnam, Inc., Lafarge, Dyckerhoff, Cemex, the Federal Highway Administration, Fibermesh Co., W.R. Grace and Co., Master Builders Technology, and the National Ready-Mixed Concrete Association. New partners are always welcome, and can contact: frohns@erols.com, edward.garboczi@nist.gov, or dale.bentz@nist.gov.
An early CIKS was designed to predict the chloride diffusivity and service life of plain portland cement concrete where corrosion of the steel reinforcement is the major degradation mechanism [1]. This article describes new systems, such as the Virtual Cement and Concrete Testing Laboratory (VCCTL), which is a CIKS that integrates many NIST models into a seamless package for using computational models to hopefully replace much of the testing that is done to develop and verify new concrete mixtures. Other available computational tools are also described.