High-Fidelity Simulation of Complex Suspension Flow for Practical Rheometry

Highly versatile and stone-like in strength, concrete is the most widely used fabricated building material. Accessing the resources of the ALCF through an INCITE award, William George of NIST is researching the flow of concrete to improve its workability and to reduce the impact of concrete production on the environment.

Over 7.5 billion cubic meters of concrete are made each year, powering a $100 billion U.S. industry. Given its predominance, there is broad interest in making concrete a more sustainable material by finding new ways to recycle it, and by reducing the amount of greenhouse gas created during its production. Architects also continue to push for enhanced workability that will allow concrete to flow easily into increasingly intricate forms. These and other improvements require that scientists first find a way to accurately and reliably measure the viscosity of concrete.

Modeling the flow of concrete presents many challenges. Concrete is a dense suspension of aggregates (e.g., sand, gravel) in a non-Newtonian fluid matrix with aggregate size ranges of several orders of magnitude. Significant effects from wide variations in the shape of the aggregates cannot be accounted for by modeling them as idealized spheres. As concrete undergoes shear flow, microstructures formed by the aggregates dynamically change as they are built and destroyed over time. The geometries of rheometers and the characteristics of the suspensions do not allow analytical solutions to relate torque and angular velocity to fundamental rheological parameters.

Results from this study at the Argonne Leadership Computing Facility will advance the science of dense suspensions and enable the measurement science needed for rheometer design with applicability to industries ranging from concrete, food processing and water treatment to coatings and pharmaceuticals.