Steady Shear Properties of Crumb Rubber Modified Bitumen

摘要

The rheological properties of crumb rubber modified bitumen poses considerable challenges in terms of quantification. This investigation concerns the measurement of shear stress and normal stress difference when samples of crumb rubber modified bitumen were tested in a dynamic" shear rheometer in a steady shear mode for a range of temperature and shear rates. Two commercially available crumb rubbers (Ⅰ and Ⅱ) were blended with an air blown bitumen. Three different dosage rates were used and the testing was carried out. It is seen that the material exhibit considerable normal stresses and normal stress difference when subjected to shear. A coarser graded crumb rubber (crumb rubber-Ⅰ) results in considerable reduction in shear stress and normal stress difference for any dosage rate, shear rate and temperature. A finer graded crumb rubber (crumb rubber-Ⅱ) results in considerable higher stress-overshoot in shear stress and normal stress difference for any dosage rate, shear rate, and temperature. For a given crumb rubber type and temperature, as the shear rate is increased, the normal stress differences increases at a much higher rate than the shear stress. These measurements clearly depict the difference in terms of crumb rubber type and dosage rates. These kinds of fundamental rheological experiments, when appropriately interpreted, shed considerable light on the interaction of crumb rubber with bitumen.