Study of the mechanical properties and self-healing ability of asphalt mixture containing calcium-alginate capsules

• Calcium-alginate capsules with a maximum payload of 75% were produced.
• Capsules without hard shell resist mixing and compaction.
• Capsules deformed and broke with loading.
• Oil diffused in the bitumen in less than 24 h.
• Large reduction of cracks around the capsules after resting 4 days at 20 °C.

The natural self-healing ability of asphalt mixtures can be enhanced with encapsulated rejuvenators: when crack damage appears the capsules release healing agents, which dissolve bitumen and drain into the cracks. In this study, the effect of a new type of capsules in the mechanical properties and the self-healing ability of asphalt mixtures is investigated. Sunflower oil was encapsulated in calcium-alginate, and protected with a hard shell made of epoxy-cement composite. Results show that the hard shell was not required for these capsules to resist mixing and compaction procedures. Capsules deformed and broke with loading, releasing oil that diffused in the bitumen in less than 24 h. Healing of cracks in asphalt mixture led to an increase of stiffness. However, asphalt specimens with capsules had lower deformation resistance. Computer tomography scanning of specimens showed large reductions in cracks around the capsules, after resting 4 days at 20 °C.

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