Evaluation of 3D printing and conventional manual techniques for crack sealing in asphalt pavements

This study compares conventional manual crack sealing with a 3D-printing-based crack sealing technique integrated with digital surface scanning, using an optimized rubber tire powder–modified asphalt binder under laboratory conditions. Surface crack geometries were captured using LiDAR scanning, and the crack geometric information was used to guide controlled sealant deposition through 3D printing, aiming to improve repeatability and reduce operator dependency in pavement maintenance. Mechanical performance was evaluated using semi-circular bending (SCB) tests for indirect tensile strength (ITS) and fracture energy, four-point bending (4PB) fatigue tests, and freeze–thaw (FT) conditioning. X-ray computed tomography (CT) was employed to assess internal filling quality, penetration depth, and continuity in both regular and irregular crack geometries. Compared with manual sealing, the 3D-printed technique achieved higher ITS (448 kPa vs. 404 kPa) and fracture energy (2647 J/m² vs. 2189 J/m²) and sustained approximately 1700 loading cycles to a 10 mm permanent deformation threshold in 4PB fatigue tests, compared with about 1250 cycles for manually sealed specimens. FT conditioning up to 5 and 10 cycles caused substantial tensile strength degradation for all specimens; although sealing improved the tensile strength ratio at low and intermediate FT levels, long-term benefits largely diminished after 10 cycles, with only marginal advantages for 3D-printed seals. CT analysis revealed deeper and more uniform sealant penetration and improved filling continuity for the 3D-printed method, particularly in irregular crack geometries. Overall, the integration of digital surface scanning with 3D printing enables geometry-adaptive, repeatable crack sealing, demonstrating strong potential as an automation-ready and scalable solution for practical pavement maintenance.