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This graphic depicts a single frame from a video simulating the flow of concrete between two walls. In this example, forces are being applied in opposite directions on the two walls, placing the concrete under shear. Various colors are used to represent rock particles of different sizes. The NIST computer models used for these concrete flow simulations may also be applicable for studying the flow of other complex fluids such as polymer blends.
Helping Concrete Go with the Flow

AS THE MOST commonly used building material comprising a $50 billion industry, concrete is big business. But for something so ubiquitous, building researchers still have a lot to learn about how to optimize the performance of concrete for specific types of jobs. For example, fresh concrete should flow smoothly for easy placement, without sacrificing strength and durability when hardened. With funding and cooperation from the private sector, National Institute of Standards and Technology researchers are studying factors affecting the flow of concrete.

The basic method for gauging concrete flow has remained essentially unchanged for a century. A standard cone-shaped mold is filled with concrete and then the mold is removed. As the concrete spreads under its own weight, its “slump” is measured.

To help develop better instruments for such tests, NIST researchers have begun simulating how concrete flows using computer models that take into account the ratio of water to cement, the amount and sizes of rocks and sand grains, and the presence of chemicals like “superplasticizers” that improve flow. This information then is used to help explain the flow behavior of different concrete mixtures in the laboratory. NIST researchers hope their results will provide a predictive tool to optimizing concrete mixtures for specific applications. //

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