A new rheological approach to evaluating the aged performance of Crumb Rubber Modified binders

Crumb Rubber Modified (CRM) binder specifications has historically relied on empirical testing with limited relationships to pavement performance. Several fundamental rheological tests have been developed in the Dynamic Shear Rheometer (DSR) with demonstrated correlation to field performance. However, these tests are conducted on aged materials to simulate in service performance through laboratory aging protocols that are not suitable for CRM binders. With the growing need for reliable performance-based characterisation of asphalt binders, a new approach to evaluating CRM binder performance is needed. This study utilises an experimental approach to introduce a new analysis methodology for evaluating performance characteristics of CRM binders. A new rheological parameter ‘Crossover Temperature’ is introduced and defined as the temperature at which the stiffnesses of CRM and residual (rubber filtered out after interaction) binders coincide. Crossover Temperature provided strong correlations to CRM binder fatigue and rutting characteristics, without the need for binder aging or micromechanical modelling. A wide range of base asphalt binders and CR sizes were utilised in this study. This parameter is recommended for Quality Control screening of CRM binders.