Sustained-release calcium alginate/diatomite capsules for sustainable self-healing asphalt concrete

Abstract

Calcium alginate capsule can gradually release the encapsulated rejuvenator after compressive loading, thus realize self-repairment of micro cracks and in-situ regeneration of aged asphalt in pavement. Nevertheless, plain calcium alginate capsules show weak mechanical strength and over-quick oil release speed and thus long-term self-healing potenial cannot be achieved. Calcium alginate/diatomite composite capsules with varying manufacturing parameters were synthesized through using orifice-coagulation method, which aims to improve mechanical strength and retard the rejuvenator release of the capsules. A series of performance tests were carried out to characterize the interior structure, thermal property, compression strength, relative rejuvenator content and rejuvenator incorporation rate of the prepared capsules. Meanwhile, the spatial location and premature rejuvenator release of capsules within asphalt concrete after manufacturing process were investigated. The rejuvenator release ratios of capsules in asphalt mixture beams after compressive loading were explored. Furthermore, the healing levels of test beams after the compressive loading and healing period were also evaluated. The calcium alginate/diatomite capsules had obvious multi-cavity structure and the diatomite with multi-pore structure offered extra rejuvenator storage units for the capsules. Meanwhile, the incorporation of diatomite could improve the thermal resistance and compressive strength and made the rejuvenator release speed of calcium alginate capsules decelerate obviously. The test beams containing diatomite modified capsules obtained acceptable healing level after long-term compression loading, which indicated that the addition of modified capsules into asphalt mixtures could realize the long-term healing of the pavement.