Self-healing properties of asphalt concrete containing responsive calcium alginate/nano-Fe3O4 composite capsules via microwave irradiation.

• Ca-alginate/nano-Fe 3 O 4 composite capsules encapsulating sunflower oil were synthesized. • Capsules within asphalt mixtures could release encapsulated oil after the action of microwave. • Oil release rate increased with the increase of microwave irradiation time and nano-Fe 3 O 4 content. • The asphalt mixtures with Ca-alginate/nano-Fe 3 O 4 capsules showed superior healing level. The responsive calcium alginate/nano-Fe 3 O 4 (CA@Fe 3 O 4) capsules can actively release the inner rejuvenator via the stimulation of microwave, thus being a prospective preventive maintenance method for effectively enhancing the self-healing level of asphalt concrete. In view of this, this paper investigated the self-healing property of asphalt mixture containing CA@Fe 3 O 4 composite capsules under the action of microwave. The CA@Fe 3 O 4 capsules encapsulating asphalt rejuvenator were fabricated based on reaction principle of ion exchange. Several tests were conducted to characterize the morphological structure, thermal stability, mechanical resistance and relative healing agent content of the capsules. Meanwhile, the spatial distribution and rejuvenator release from the capsules in asphalt mixtures after mixing and compaction process were also explored. Besides, the surface temperature distribution and self-healing capacity of asphalt concrete beams without and with capsules were investigated after microwave action. Meanwhile, the rejuvenator release ratios of capsules within mixture beams were also quantificationally analyzed. The experimental results indicated that the CA@2%Fe 3 O 4 capsules showed multi-cavity structure with healing agent stored inside. Meanwhile, the mechanical resistance and thermal stability of the capsules all were up to the manufacturing requirements of asphalt mixtures in laboratory. The asphalt mixtures with CA@2%Fe 3 O 4 capsules showed superior healing level under the action of microwave due to the combined effect of thermal induction and rejuvenator healing. In short, the CA@2%Fe 3 O 4 capsules can obviously enhance the self-healing capacity of asphalt mixture compared with normal CA capsules. [ABSTRACT FROM AUTHOR]