A 3-D image of a cement paste with a resolution of 1 micrometer.
An image of the same paste that has been virtually hydrated for several hours.
Even in the toughest economic times, producers can not afford to de-emphasize quality control. The concrete industry has been approaching mix designs and material selection in practically the same way for decades. But should this change?
Do you dream of how to improve your quality control program? Would you like to know how a new source of cement or aggregate will affect concrete pumpability without doing lots of slump tests? Do you imagine a tool that could give you advanced warning of chemical incompatibilities in concrete made with blended cements?
Have you wished you could predict how to optimize your mix design cost and performance for a particular commercial project? And after encountering odd testing results, would you like to explain these findings quantitatively so you could understand and use these formerly puzzling results?
Most of the answers are based on studying or testing the ingredients used in the mix design and how they relate to one another. And as most producers know, such work can be tedious and lengthy. Often the answers are discovered well after the project is completed.
Fortunately, help is on the way. In the last 30 years, researchers have been working in computational materials science. The goal is to apply materials science theory to analyze complicated materials like construction materials via the modern computers.
In the last few years, computational materials science has grown in effectiveness and range. Faster computers have revolutionized how researchers can analyze results. Information technology has yielded better hardware and faster algorithms. Quantitative theory based on fundamental materials science has been successfully applied to guide research and develop new materials in the pharmaceutical, metals, and semiconductor industries.The case of concrete
Unfortunately, quantitative theory for concrete materials has not advanced to the same level. Construction materials like aggregates, portland cement, and supplementary cementitious materials such as slag and fly ash are much too complicated for straightforward application of basic materials science.
But thanks to an innovative project, researchers are narrowing this gap. Our industry's leading hope for a computational materials science tool for concrete is the Virtual Cement and Concrete Testing Laboratory (VCCTL).
VCCTL is a large, integrated software package that mimics a complete physical testing laboratory. It's filled with databases of cements and aggregates instead of bins and hoppers. It contains computer programs that combine materials. Once mixed, there's a concrete curing model instead of curing rooms. And a user-friendly software interface, instead of a cart, takes materials and samples around the laboratory, where accurate models for performance prediction are applied, instead of instrumented testing machines.
VCCTL is being developed at the National Institute of Standards and Technologies (NIST), a non-regulatory agency within the U.S. Commerce Department. Partners are the Ready-Mixed Concrete Research and Education Foundation, the Federal Highway Administration, BASF, Mapei, Sika Technology AG, and W.R. Grace. Pervious supporters are PCA, Holcim, Cemex, Dyckerhoff, and the National Stone, Sand, and Gravel Association.