Study On The Self-healing Performanc And Mechanism Of Asphalt Concrete Under Microwave Radiation

As the main pavement form of high-grade roads,asphalt concrete consumes billions of yuan each year due to environmental and traffic damages.And the microwave heat-induced pre-maintenance technology based on the self-healing characteristics of asphalt can quickly repair the cracks by heating up multiple times to avoid the emergence of macroscopic diseases and save maintenance costs.However,researches on the enhancement of overall thermally induced properties of asphalt concrete,quantification of key indicators for self-repairing effects,and discussion of the mechanism of thermally-induced self-repairing are still lacking.Thus,this paper designed all-component absorbing asphalt mixtures.Combined with properties of constituent materials,comparison of heating efficiency,quantification of self-healing parameters,and simulation of electromagnetic field distribution,the self-healing performance and mechanism of asphalt concrete were studied.The main conclusions reached are as follows:（1）The physical and chemical properties of Fe₃O₄ treated at different temperatures indicate that the temperature change（≤150°C）can enhance the microwave heat-induced characteristics of Fe₃O₄.The high and low temperature rheological performances were carried out on modified bitumen with different content of Fe₃O₄.The results show that the optimal content of Fe₃O₄ in asphalt concrete that meets the performance requirements is 1.0%of the quality of pure bitumen.（2）The all-component absorbing asphalt mixtures are composed of pure bitumen containing 1.0%Fe₃O₄ and aggregates which are steel slag and basalt,separately.A comparison sample of asphalt concrete composed of pure bitumen and limestone aggregate.Road performance indicates that combination of Fe₃O₄,absorbing fillers and aggregates does not adversely affect the road performance of asphalt concrete.（3）From the perspective of asphalt mortar in asphalt concrete,based on the flow behavior index and frequency sweep experiment,the initial self-healing temperature was explored.Results show that the all-component microwave absorbing asphalt concrete has a lower value.The infrared images after heating show that the heating rates of all-component absorbing asphalt concrete reach 6.74 and 8.99 times of limestone asphalt concrete,so it can be faster reach an efficient flow state at the initial self-healing temperature and close the crack quickly.（4）Based on the initial self-healing temperature,fracture-healing-refracture tests and heating rate,the healing efficiency and period were quantified.The healing level of asphalt mixture contained limestone is lower than 30%,and the maximum healing level of 72.1%after 60 s 75.6%after 40 s are reached for full-component absorbing asphalt mixture containing steel slag and basalt,but the shorter healing period and the long-term heat-induced high temperature damage to the strength of the concrete structure reduce the self-healing efficiency of the full-component absorbing asphalt concrete containing basalt after long-term thermal induction,the maximum temperature during thermal induction should be controlled below 120°C.（5）Based on the results of the electromagnetic properties of the constituent materials,the electromagnetic parameters of asphalt concrete were quantified.It shows that the addition of Fe₃O₄ offsets the weakening of the electromagnetic performance of the bitumen,and enhances the microwave loss of asphalt concrete.After substituting the electromagnetic parameters into the HFSS,the electromagnetic field and microwave loss distribution of asphalt concrete under microwave radiation were solved.The loss obtained through the model is compared with the loss shown by the heating rate and the self-healing efficiency in the actual microwave radiation.（6）Based on the model and actual results,combined with the action mechanism and transmission mechanism microwave radiattion,the self-healing mechanism of asphalt concrete was revealed.The results show that compared with limestone asphalt concrete,all-component absorbing asphalt concrete not only has less reflected and transmitted microwave,but also more microwave loss due to better electromagnetic parameters,which can quickly warm up the concrete and reduce the viscosity of asphalt mortar,and close cracks to improve the self-healing efficiency of concrete.The research results of this paper can provide new ideas for pavement maintenance technology,reduce energy consumption and costs of road maintenance,and promote sustainable development of the transportation industry.