Innovative dual-functional microcapsules for bitumen materials: Integrating phase change thermal regulation and self-healing improvement

This study presents an innovative microcapsule system that simultaneously enables phase-change thermal regulation and autonomous self-healing in bitumen pavements. Using optimized in-situ polymerization, we engineered microcapsules with a hexadecane core (18.1 °C phase transition, 237 J/g latent heat) encapsulated in a robust HMMM shell (2–3 μm thickness). Structural characterization (FT-IR, electron microscopy) confirmed uniform spherical morphology (15–25 μm diameter). The microcapsules demonstrated outstanding thermal stability, retaining 95.8 % enthalpy after 500 thermal cycles (-10 °C to 60 °C) and resisting degradation up to 250 °C. When incorporated into bitumen at 5.0 wt%, the system reduced peak surface temperature by 12.3 °C under 1 kW/m² radiation while improving aging resistance (14.7 % lower G* after RTFO/PAV). Penetration tests showed enhanced temperature susceptibility, with aged modified bitumen stabilizing at 32–41 dmm versus 35–60 dmm for conventional bitumen. At 10.0 wt%, the softening point increased to 56.8 °C, confirming superior high-temperature stability. The self-healing efficiency reached 55.2 % at 20 °C (BOEF test), with consistent performance over multiple cycles (57 %→52 % after six cycles). Nano-XCT verified homogeneous dispersion, and interfacial analysis indicated strong microcapsule-matrix bonding. Crucially, the phase-change behavior facilitates crack repair by creating optimal thermal conditions for healing. This dual-functional system offers a holistic solution for pavement durability, extending service life while minimizing maintenance—a transformative advancement for sustainable infrastructure.