Investigation of rheological properties and Superpave PG of PMB mixed with reclaimed asphalt pavement binders

- Performance of PMB deteriorates with addition of RAP binders.
- RAP binder sources had different influence on physical properties of PMB.
- Inclusion of RAP binder reduces the temperature susceptibility of PMB.
- Addition of 15%, 25% and 40% of RAP binder enhanced high PG of PMB by one grade interval, while no change was found in low PG.

The present study was undertaken to evaluate the effects of two types of reclaimed asphalt pavement (RAP) binders on rheological properties and Superpave performance grade (PG) of a styrene-butadiene-styrene (SBS) co-polymer modified binder (PMB). Two RAP materials: one from urban highway (RAP-A) and other from rural highway (RAP-S) were collected in the study. The asphalt binder extracted from RAP-A and RAP-S had different viscosity, rheological and chemical characteristics. The asphalt binder extracted from RAP-A was found to be stiffer compared to the binder obtained from RAP-S. The PMB was blended with different proportions (i.e., 0, 15, 25 and 40% by weight of binder) of RAP-A and RAP-S binders. Different physical tests, namely penetration, softening point, viscosity, ductility and elastic recovery were conducted on PMB blended with the RAP binders. In addition, high and low temperature Superpave PG of PMB with RAP blended binders were determined based on dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, respectively. The results from physical properties of asphalt binders showed that addition of RAP binders adversely affected performance of PMB. Both type of the RAP binders had difference influence on physical properties of PMB. Addition of 15% of RAP bumped PG of PMB by one grade interval (i.e., from PG76 to PG82). The maximum grade bump for high temperature PG was found to be one grade interval even after addition of 40% RAP. The low PG grade did not change with addition of the RAP binders. Statistical analyses were conducted to compare effects of two types of RAP binders on properties of PMB. Overall the results showed that type of the RAP binder can have different influence on consistency and Superpave PG of PMB, thus caution should be taken during selection of grade of a base binder.