Determining elastic properties of reclaimed asphalt pavements (RAP) from indirect tensile test and full-field measurement technique

This study investigates the elastic mechanical properties of asphalt mixtures containing various proportions of reclaimed asphalt pavement (RAP) by combining the indirect tensile test (Brazilian test) with a full-field strain measurement technique. Five mixtures with identical aggregate grading, binder content and richness modulus, but different RAP percentages, were evaluated. Full-field strain maps revealed highly heterogeneous microstructures, characterized by rigid aggregates and deformable binder-rich zones, yet the analytical method used enabled the extraction of consistent macroscopic elastic parameters. Strain analyses demonstrated that a minimum virtual gauge length of approximately 20 mm is required to reach a representative measurement scale. Results show that Young’s modulus increases almost linearly with RAP content, reflecting the stiffening effect of aged binder, whereas Poisson’s ratio decreases, indicating reduced lateral deformation capacity. These trends were robust over different virtual gauge lengths. The Grid Method proved particularly suitable for characterizing strain heterogeneity and for determining elastic properties without the limitations inherent to physical strain gauges. The proposed methodology offers a reliable framework for analysing heterogeneous asphalt mixtures and provides a foundation for future studies involving alternative loading configurations, micromechanical modelling, rejuvenated binders or extended RAP contents.