Aging-induced embrittlement, fatigue cracking, and moisture damage are among the primary factors limiting the long-term performance of asphalt pavements. This study investigated the effects of heavy-oil-containing capsules and Nano Zycosoil surface treatment on the mechanical performance, moisture susceptibility, and fatigue behavior of asphalt mixtures. Five mixture groups were prepared: a control mixture, a mixture containing untreated capsules, a mixture containing Nano Zycosoil-treated capsules, a mixture containing treated aggregates and untreated capsules, and a mixture containing both treated aggregates and treated capsules. The optimum asphalt content of each group was independently determined using the Marshall method. The mixtures were evaluated through Marshall stability, indirect tensile strength, tensile strength ratio (TSR), indirect tensile fatigue, and boiling-water tests. In addition, the thermal stability and structural characteristics of the capsules were examined using thermogravimetric analysis (TGA), computed tomography (CT), and scanning electron microscopy (SEM).

Short-term aging decreased binder penetration from 48 to 35 dmm and ductility from 135 to 107 cm, while increasing the softening point from 51.5 to 54 °C. The incorporation of untreated capsules alone reduced indirect tensile strength and fatigue life relative to the control mixture; however, surface treatment of the capsules recovered a substantial portion of this reduction. The mixture containing both Nano Zycosoil-treated aggregates and treated capsules exhibited the best overall performance, achieving a Marshall stability of 1400 kg, dry and moisture-conditioned indirect tensile strengths of 1.884 and 1.815 MPa, respectively, a TSR of 96.34%, and a fatigue life of 112,827 cycles. Its fatigue life was 39.64% higher than that of the control mixture. Furthermore, the estimated retained asphalt coating in the boiling-water test increased from 43% for untreated aggregates to 95% for treated aggregates. Overall, the simultaneous surface treatment of aggregates and capsules provided the most effective improvement in mechanical performance, moisture resistance, and fatigue durability.