Performance Evaluation of Intermediate and Base Asphalt Mixtures in Virginia

About the project

The Virginia Department of Transportation (VDOT) has implemented a balanced mix design (BMD) specification for the design and acceptance of dense-graded asphalt surface mixtures (SM) with A and D designations. The BMD specification incorporates performance tests and corresponding criteria to screen out potentially poor-performing mixtures by balancing their cracking and rutting resistances during mix design. Since the BMD specification is applicable to SMs, it does not address potential deficiencies of the underlying asphalt layers such as asphalt intermediate mixtures (IMs) and base mixtures (BMs).

The IM and BM layers correspond to most of the material used in the asphalt concrete pavement and, thus, have a key role in the pavement structural capacity. Nonetheless, IMs and BMs are not often included in routine maintenance schedules. Besides, changes in the mix design and in-place density requirements for BMs starting in 2026 may lead to changes in BMs expected performance, potentially impacting the decision-making during pavement design. Collectively, these factors highlight the need to design and produce good-performing IMs and BMs.

The goal of this study is to benchmark the performance of IMs and BMs with respect to fatigue cracking and rutting resistances and evaluate mix design strategies to potentially improve the performance of BMs, such as incorporating the recycled binder availbility (RBA) concept during mix design. The scope of work will include analyzing VDOT's mix design, production, and in-place density data, performing laboratory tests (index-based and fundamental), and conduct pavement performance simulations.

Better understanding the performance of these mixtures will not only contribute to the design and production of structurally sound pavements but will also support a succesful and responsible BMD implementation for SMs.

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