Practical Laboratory Aging Protocol for Cracking Evaluation of Asphalt Surface Mixtures in Virginia

The Virginia Department of Transportation (VDOT) has implemented the Balanced Mix Design (BMD) concept for its dense-graded surface mixtures to improve the durability and service life of asphalt pavements. The VDOT’s BMD framework specifies the use of the indirect tensile cracking test to assess the cracking susceptibility of asphalt mixtures, requiring a minimum cracking tolerance (CT) index of 70 after short-term oven aging for 4 h at compaction temperature (T comp ). However, the current framework does not account for oxidative aging over the service life of asphalt mixtures, which is becoming increasingly relevant with the use of additives and recycled materials. This study aims to develop a practical laboratory long-term aging protocol to be used in the VDOT’s BMD framework, while balancing the need for an effective differentiation of asphalt mixtures’ performance and ensuring a practical implementation in routine laboratory settings. This study includes 10 asphalt mixtures with varying reclaimed asphalt pavement contents and asphalt binder performance grades. The asphalt mixtures underwent laboratory oven aging at 95°C and 135°C or higher (i.e., T comp ) to determine appropriate aging durations. The CT index of the asphalt mixtures was measured alongside the rheological and chemical properties of the virgin and recovered asphalt binders. This study identified a reduced aging duration at 95°C and established an equivalent accelerated aging duration at T comp . Preliminary criteria for the CT index were also developed based on the observed relationship between the CT index of the asphalt mixtures at different aging conditions and their corresponding Glover–Rowe parameter of recovered asphalt binders.