Asphalt cements are graded, specified, and purchased in large part according to their rheological properties. Asphalts from different sources have different chemical compositions, which affect their rheology. Compositional variations also affect the interactions of asphalts with modifiers such as elastomeric and plastomeric polymers, polyphophoric acid, hydrated lime, and anti-strip additives. Pavements with desirable rheological properties resist permanent deformation (rutting, shoving) at high pavement temperatures, remain durable at moderate temperatures, and resist low-temperature cracking by relaxation of thermal stresses.
WRI uses rheological techniques to investigate the influence of chemical composition on asphalt physical properties. With time and exposure to environmental conditions, asphalts oxidize and age, causing changes to their chemical composition. Rheological properties of asphalts are measured using dynamic shear rheology at moderate and high pavement temperatures and using steady-state measurements (Brookfield) at asphalt-aggregate mixing temperatures. Low-temperature rheological measurements of asphalt are performed using a bending-beam rheometer.
Asphalt samples are analyzed using frequency sweep dynamic shear rheology at several temperatures in order to construct master curves of asphalt properties. Rheological data can be fit to the CAM model, the WLF model or others and are used with chemical, physical, and spectroscopic data from other analytical techniques to increase understanding and improve the science of predicting pavement performance from material properties.
Rheological measurements provide important insight into performance properties of materials. WRI can perform frequency sweep dynamic shear rheology, steady-state rheology, and multiple stress creep recovery (MSCR) testing over a wide temperature range on asphalt and other materials. On asphalt, we can also perform low-temperature bending beam rheology. What’s more, WRI can perform ultra-low torque and torsion-rectangular rheological measurements on a variety of materials.