Design and Manufacture of Self-Healing Asphalt Concrete with Capsules.

This study focuses on the design of self-healing asphalt concrete with capsules, taking into account their size and the particle size distribution of the mineral components. A practical application of this approach is demonstrated for the production of A16UL asphalt concrete with calcium alginate capsules containing a thiol-containing urethane AR polymer (ARP) for a pilot road section. The results show that self-healing efficiency depends strongly on the granulometric composition and void structure of the asphalt mixture. For the selected A16UL mixture, the void network was sufficient to accommodate 1.1 mm capsules while maintaining a high capsule survival rate of 96% after compaction. Tomographic analysis confirmed a uniform distribution of capsules in the pavement structure, with less than 5% of capsules located too closely to be considered well dispersed. The use of ARP-filled capsules increased the recovery of compressive strength after healing to 38.8% of the residual strength, corresponding to 99.9% recovery of the initial strength, whereas the control mixture reached only 78.6%. In addition, the self-healing rate increased by a factor of 2.5 compared with the unmodified composition. The proposed approach demonstrates that self-healing asphalt concrete can be produced without changing the conventional production chain, provided that mixture design and capsule size are properly matched. The obtained results allow designing various types of asphalt concrete with capsules to extend the service life of pavements without repair.