Investigating and Understanding the Effects of Reclaimed Asphalt Pavement and Shingles on the Rheology and Performance Grading of Asphalt Cement.
The incorporation of Recycled Asphalt Pavements (RAP) and Shingles (RAS) into neat asphalt binder is a useful development towards environmental sustainability apart from its economic savings benefits, which comes as a relief to the finances of the transportation sector. Recycling of pavements reduces the demand for non-renewable resources such as new asphalt binder and mineral aggregates. Unfortunately, there are no protocols to control and guide the sector or contractors on the appropriate and effective amount of RAP/RAS that can be used, which has created a monitoring problem on its usage. The effects that RAP (Highway 7, 11, 403) and RAS have on the rheology of two sources of virgin asphalts of the same grade was studied under this research. Two binders of grade PG 58-28 were modified at different percentages (10%, 20% and 30%) of RAP and RAS. To simulate aging that occurs during Hot Mix Asphalt (HMA) production, laying and compaction and aging that occurs during service life, the modified binders were subjected to Rolling Thin Film Oven (RTFO) aging and Pressure Aging Vessel (PAV) aging. Rheological properties before and after modification and aging were measured using the Dynamic Shear Rheometer (DSR). The resistance to fatigue cracking, permanent deformation, the performance at high and intermediate temperature were accessed using the DSR. The Fraass Breaking Point (FBP) instrument was used to determine the temperature at which cracks initiate which is related to the fatigue resistance in asphalt binders. The extent of oxidation after modification and aging was determined using the Fourier Transform Infrared (FTIR) spectrometer. The Modulated Differential Scanning Calorimetry (MDSC) technique was used to study the changes in glass transition temperatures between the different RAP/RAS at the same modification dosage and aging. The binder increased in stiffness as the percentage of modification increased and this differed with each RAP/RAS source. The binders showed it could take more than 30% dose of Highway 7. Highway 403 RAP and the RAS, from results, are unsuitable for surface course pavement construction. The aging effect was very prominent after aging the samples in the PAV for 40 hours as compared to the standard 20 hours. It was found that the determination of the low temperature performance of a binder using the limiting phase angle temperature at 30 is promising.