Nonlinear Viscoelastic Response Assessment of Sustainable Asphalt Binders Containing Guayule Resin and Crumb Rubber Using MSCR and Interrupted Shear Flow Tests

This study evaluated the nonlinear viscoelastic (NLVE) response and structural recovery characteristics of sustainable asphalt binders incorporating guayule resin and crumb rubber modifier (CRM). Capturing NLVE behavior is critical to represent field-like conditions under heavy traffic and high temperatures, conditions where traditional linear metrics fail to distinguish binder performance. By assessing guayule resin’s potential, the study addresses the growing demand for environmentally responsible materials in modern pavement design. The experimental matrix included sixteen binders: nine asphalt–rubber–guayule (ARG) blends with varying AR and CRM dosages, five corresponding asphalt–rubber–asphalt (ARA) controls, and two neat references. Performance was evaluated using Multiple Stress Creep Recovery (MSCR) and Interrupted Shear Flow (ISF) tests, capturing elastic recovery, stress sensitivity, and structural reorganization, supported by DSR-based rheology and viscosity profiling. This comprehensive testing framework offers insights into both nonlinear and linear binder behavior. MSCR results demonstrated that although ARG binders exhibited measurable elastic recovery and nonlinear response, they were generally outperformed by their corresponding asphalt rubber binders in terms of percent recovery and stress sensitivity. However, several ARG formulations still matched or exceeded the performance of the control asphalt binder, indicating their viability as sustainable alternatives. ISF testing further highlighted the unique recovery capacity of guayule–rich binder through rebuilding internal structure within 5 to 10 seconds of rest, behavior not captured by conventional testing or observed in asphalt rubber binders. These findings underscore the active role of guayule resin in nonlinear recovery and structural resilience, supporting its use in sustainable binder technologies.