Influence of Binder Source and Recycled Asphalt Materials on Asphalt Binder Relaxation Properties for Northern Climates.

Low-temperature pavement performance is important in freezing areas in northern climates. While agencies and contractors pursue efforts to add recycled asphalt materials (RAMs) into the mix design to reduce costs, the aged, stiffer material being blended in can dramatically alter the performance. A correlation between the Glover–Rowe parameter (G–R) and delta T_c (ΔT_c) was developed in 2011 by Anderson et al. to relate the onset of nonload-related and significant cracking values. The relationship provides a correlation between nonload-related and low-temperature cracking properties of the binder. To further evaluate this relationship, four cold-region virgin binders from Wisconsin and Michigan were blended with varying percentages of RAM mixtures. Blends were then laboratory aged tested to obtain stiffness, m-value, complex shear modulus, and phase angle from BBR and DSR testing, allowing for the calculation of ΔT_c and the G–R parameters. Investigation of their correlation for each binder source and the change in ΔT_c was evaluated for each blend. Updated correlations and trends show that correlations are source dependent, suggesting that the ΔT_c specification maxima should be re-evaluated for their inclusion of RAP sources. [ABSTRACT FROM AUTHOR]