Improvement of toughness and road performance of unsaturated polyester resin asphalt pavement crack sealant through liquid rubber/nanoclay hybrid toughening

Abstract To more effectively repair cracks and reduce maintenance costs, an unsaturated polyester resin (UPR) sealant, RMUP, hybrid toughened by liquid nitrile rubber and nanomontmorillonite, was developed. The optimal preparation procedure was proposed based on the results of an orthogonal test concerning the impacts of preparation procedure parameters (sequence of modifier addition, stirring speed, and time) on its mechanical properties. The adaptability and effectiveness of RMUP for repairing pavement cracks were assessed through a series of performance tests on composite specimens repaired by RMUP sealant, including bonding performance test, low‐temperature cracking resistance test, water‐induced damage resistance test, and fatigue resistance test, as well as contrastive analysis with other available sealants. Furthermore, the toughening mechanisms involved in RMUP were elucidated with the aid of FTIR and SEM to characterize its molecular structure and fractography. The results demonstrate that RMUP sealant has superior bonding and shear strength, measuring 0.86 and 1.04 MPa, respectively, and shows favorable applicability in crack repair. The sealant can effectively and durably bond cracked pavement structures and yield repaired pavement structures with excellent resistance against water‐induced damage and fatigue. The fractography reveals that the increased toughness of RMUP is attributed to the additive toughening effect of rubber particles and nanomontmorillonite. In addition, the cross‐linking of nitrile rubber molecular chains with UPR polymer chains and the intercalation of UPR polymer chains into nano‐montmorillonite galleries further contribute to the enhanced toughness of the UPR matrix. Highlights The addition order of modifiers impacts the mechanical properties of composites. RMUP effectively and durably bonds cracked pavement structures. The cross‐linking of liquid nitrile rubber with the matrix polymer chains improves composite flexibility. The clay–polymer intercalation structure promotes the matrix's toughness. Multiple toughening mechanisms coexist in RMUP and have an additive toughening effect.