Sustainable asphalt mixtures design: Balancing environmental impact, cost, volumetric and performance considerations

Asphalt mixture design must balance mechanical performance, life-cycle cost, and environmental impact, particularly when incorporating sustainable technologies such as warm mix asphalt (WMA), reclaimed asphalt pavement (RAP), and rejuvenating agents (RA). This study proposes a four-dimensional Balanced Mix Design framework (BMD-4D) that integrates volumetric feasibility with mechanistic pavement performance, life-cycle cost analysis (LCCA), and life-cycle assessment (LCA). A factorial program spanned multiple volumetric states in the VMA-VFA domain, including HMA/WMA production, RAP incorporation, and RA use. Mixtures were characterized through dynamic modulus and cyclic fatigue testing, while rutting susceptibility was quantified using the Stress Sweep Rutting test and a permanent deformation Shift Model. Pavement-scale fatigue and rutting lives were predicted via mechanistic-structural simulations and converted to cracked area and rut depth through calibrated transfer functions. Cost and global warming potential (GWP) were quantified at the project scale by coupling LCCA with cradle-to-use LCA, including use-phase effects via pavement-vehicle interaction modeling. Response surfaces were calibrated for Performance-, Cost-, and Environmental-Volumetric Relationships, enabling optimization under specification constraints. Two pathways were compared: a single-index efficiency approach using monetized environmental externalities and a multi-objective Non-dominated Sorting Genetic Algorithm II (NSGA-II) formulation generating a Pareto front. Pareto-optimal solutions were ranked using the entropy-weighted Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), identifying a compromise volumetric target within the feasible region. Monte Carlo uncertainty propagation produced a joint Probability of Success field, delineating a robust design space where all thresholds are simultaneously met. The framework provides a transparent methodology to support sustainable mixture selection under volumetric feasibility and uncertainty. The framework is demonstrated for a single mixture family produced with one aggregate source, one binder grade, one WMA additive, one rejuvenating agent and a single RAP source at 20% content; the reported technology effects are therefore specific to this material system, and broader calibration and field validation are required before the numerical trends are generalized. The contribution reported here is therefore a demonstration of the methodology on one material system rather than a calibrated design tool of general applicability.