Descriptive comparison of fatigue performance in asphalt mixtures containing reclaimed asphalt pavement using combined activation treatments

This study examined fatigue damage evolution in asphalt mixtures containing 48% Reclaimed Asphalt Pavement to determine how RAP material characteristics and combined activation treatments influence dry and moisture-conditioned fatigue performance. Three RAP materials, Urban Arterial, Highway Corridor, and Industrial Pavement, were each combined with Low, Medium, and High activation treatments that simultaneously varied rejuvenator dosage, mixing temperature, and compaction temperature, producing nine formulations. Dry specimens were tested at 400 and 500 microstrain, while freeze-thaw-conditioned specimens were tested at 500 microstrain. RAP characterization included binder content, penetration, softening point, viscosity, carbonyl index, sulfoxide index, and fine fraction. Performance evaluation included volumetric properties, Indirect Tensile Strength, Tensile Strength Ratio, Retained Modulus, fatigue life, dissipated energy, normalized stiffness damage, Fatigue Life Retention, and Normalized Fatigue Loss. The Medium treatment produced the highest fatigue life within each RAP material. HC_M achieved the highest N₅₀ values of 81,726 cycles at 400 microstrain, 28,451 cycles under dry conditions at 500 microstrain, and 22,983 cycles after freeze-thaw conditioning. HC_M also achieved a Tensile Strength Ratio of 90.1%, Retained Modulus of 87.5%, Fatigue Life Retention of 80.8%, and Normalized Fatigue Loss of 19.2%. Increasing strain from 400 to 500 microstrain reduced fatigue life by 65.2% to 70.3% across the tested formulations. These results indicate that moderate combined activation provided the most favorable balance of moisture resistance and fatigue durability among the tested 48% RAP mixtures.