Assessing the Impact of Storage Time at Elevated Temperatures on Degree of Blending in High RAP Mixes with Bio-Based Rejuvenators

In Canada, asphalt concrete is used in the construction of about 90% of pavements. A common practice used to improve the sustainability of flexible pavements through reducing their environmental impacts and cost over their lifetime is incorporating Reclaimed Asphalt Pavement (RAP) in the production of new asphalt mixes. Degree of Blending (DOB) between RAP and virgin binder plays a critical role in the performance of resulting mixes. Therefore, it is essential to quantify and understand factors affecting DOB to optimize the performance of RAP mixtures. The purpose of this study was to evaluate the effect of storage time at elevated temperatures, on enhancing the DOB in these types of mixes, using Attenuated Total Reflection—Fourier Transform Infrared (ATR-FTIR) spectroscopy and Dynamic Shear Rheometer (DSR). Different asphalt mixes were produced with 50% RAP, virgin HL3 aggregates, PG 58-28 virgin binder, and two bio-based rejuvenators. A gap gradation method was used to allow for easy separation of RAP and virgin aggregates after mixing, based on size differences. Control mixes (without rejuvenator) underwent four types of conditioning, 4 and 8 h at 135 and 110 °C. Based on the findings of the control mix, the rejuvenated mixes were exposed to two conditioning states, 4 h at 135° and 110 °C. Thereafter, the mixes were separated into RAP and virgin aggregates, and binder recovered from each separately. The recovered binder was evaluated using ATR-FTIR and high PG DSR testing. The results were used to estimate DOB and study the correlation between chemical and rheological properties. On comparing the test results the optimal storage time and temperature for maximizing DOB was found to be 4 h at 135 °C. It was also concluded that carbonyl indices showed a good linear correlation with high PG measurements.