Study On Preparation Of Multi-chamber Self-healing Capsule And Its Effect On Performance Of Asphalt Concrete

Asphalt concrete is a kind of self-healing material,which can heal automatically when cracks occur inside.However,it is difficult to heal the cracks due to low temperature and aging in the actual service process.To improve the self-healing performance of asphalt concrete,heat-induced and microcapsule self-healing technologies have been developed.Yet,heat-induced self-healing technology can not solve the aging problem of asphalt due to its low heating efficiency,and the self-healing technology of microcapsules is limited because of its low content of repairing agent and the limited number of self-healing times.In order to solve these problems,a millimeter-scale capsule with multi-chamber structure and high content of repairing agent was designed,and its effects on pavement performance,self-healing performance and in-situ rejuvenate performance of asphalt concrete were studied.Firstly,self-healing capsules with different water-oil ratios?20:1,10:1,7:1 and3:1?were prepared by ion-exchange method using emulsion of 2.5%sodium alginate solution,Tween 80 and sunflower oil with 3%CaCl₂.The inner structure of the capsules was multi-chamber structure.With the decrease of water-oil ratios,the radius,thermal stability,the content of repairing agent and the size of inner chamber of the capsule increased,while the density,mechanical strength and survival rate of the capsule after mixing and compacting decreased.By optimizing the parameters,it is considered that the self-healing capsule with water-oil ratio of 10:1 is most suitable for mixing into AC-13 asphalt concrete,and the survival rate after mixing and compacting is more than 95%.Then,the influence of the content of multi-chamber self-healing capsule?0%,0.5%,0.75%and 1%?with water-oil ratio of 10:1 on the pavement performance of AC-13 asphalt concrete was studied.With the increase of capsule content,the low temperature crack resistance of asphalt concrete increases slightly,while the high temperature stability decreases.When a small amount of capsules?0.5%?are added,the moisture damage resistance and fatigue properties of asphalt concrete will not be affected,too many capsules will reduce the water stability and fatigue properties of concrete.Therefore,0.5%of the total mass of asphalt concrete is the best content of the capsule for AC-13 HMA.Finally,the self-healing and regeneration properties of asphalt concrete with 0.5%capsule were studied.The release of sunflower oil in the capsule has obvious stress control characteristics,and gradually releases with the increase of fatigue load,which significantly improves the self-healing ability and regeneration of asphalt concrete.After 6000 fatigue loads under 2.1MPa,sunflower oil released 77.2%,the three-point bending strength recovery rate of untreated asphalt concrete reached 92.7%,and the fracture energy recovery rate reached 180%.Aged asphalt can be regenerated,and its components can be restored to the same level as untreated asphalt.The results show that the multi-chamber self-healing capsule can improve the self-healing ability of asphalt concrete while realizing the in-situ regeneration of aged asphalt.It is of great significance to improve the intelligent level of asphalt pavement,reduce the workload of pavement maintenance and improve the service life of asphalt pavement.