Are we correctly measuring the rotational viscosity of rubberized bituminous binder?

Description

Are we correctly measuring the rotational viscosity of rubberized bituminous binder?

 Gaspare Giancontieri, David Hargreaves, Davide Lo Presti

ABSTRACT. A detailed rheological characterisation of Recycled Tyre Rubber Modified Bitumen’s (RTR-MB) is of paramount importance for their modelling, formulation, processing and performance. Nevertheless, adding crumb rubber to the base bitumen, further than improving the material characteristics can also represent an issue for rheologists. In fact, due to their complex structure, obtaining reliable rheological measurements sometime could be a challenge. Previous works have shown that when standard testing geometries and configurations are used for such complex systems a number of changes may occur within the measuring chamber during the test. These changes all contribute to undermine the sample stability that if altered can provide significantly misleading results. This study emphasizes this aspect by providing a deeper understanding of the phenomena happening during rotational testing of neat and rubberized bitumen at high temperatures, as well as questioning the reliability of the results. The investigation will present the results of a combined laboratory-based and computational approach, focused on highlighting whether by using standard tools samples undergo lack of stability. Results will also highlight that using a novel testing configuration allows recording more realistic and stable viscosity measurements.

Keywords: Recycled Tyre Rubber, Sample stability, Dual Helical Ribbon, modified bitumen