Study On Fracture Healing Performance Of Asphalt Mixture Based On Microwave Heating

Cracking is one of the main diseases of asphalt pavement.The existence of cracks will make a negative impact on the structure and functionality of the pavement,and shorten the service life of pavement.The problem of pavement cracking has always been one of the hotspots in pavement research.Using the characteristic of self-healing,some kinds of heating methods are adopted to heat and curing the asphalt pavement,repair the internal micro damage,close the cracks and extend the service life of the pavement,which is an advanced maintenance concept advocated by the United States,the Netherlands and other developed countries in recent years.In this paper,microwave healing performance of asphalt mixture after fracture was studied.The aggregate,mineral powder,asphalt mortar,asphalt mortar and asphalt mixture were tested by microwave heating.The results showed that the microwave heating rate of aggregate increased with particle size,and the contribution of coarse aggregate to the overall heating of asphalt mixture was greater than that of fine aggregate and mineral powder.The heating rate of AC-20 mixture was higher than that of SMA-13mixture and AC-13 mixture.The temperature rising rates of AC-13 mixture prepared by matrix asphalt binder,SBS modified asphalt binder and composite modified(CM)asphalt binder were similar,which showed that the two kinds of modified asphalt binder used in the study do not absorb microwave,just like matrix asphalt binder.In the indoor test,it was necessary to control the microwave heating time to avoid the local overheating of the test specimen due to long-time microwave heating,which might lead the softening and deformation of test specimen.In the study,the maximum heating time is 160s at 700W,and the average temperature of the specimen surface reaches 78℃～90℃.the failure load ratio HI_P and fracture energy ratio HI_U were defined as the healing evaluation indexes,and the microwave healing performance of asphalt mixture after macro cracking was evaluated from the perspective of mechanical strength and energy through the SCB test.The results showed that the asphalt mixture with macro cracks could be healed under microwave radiation,and the healing indexes were between 0-1,which indicated that the mechanical properties of the semicircle specimen could be restored to a certain extent.After heating for 160s under 700W,the healing indexes of the asphalt mixture could reach 40%～70%.In a certain range,the healing indexes increased linearly with microwave power or heating time.Increasing microwave power or heating time could effectively promote the self-healing behavior and improve the self-healing effect.The differences of asphalt type and gradation type would also cause the differences of microwave healing performance.Among the five kinds of asphalt mixtures used in the study,SBS AC-13 asphalt mixture had the best microwave healing performance,while SBS AC-20 asphalt mixture had the worst microwave healing performance which was mainly due to the different asphalt healing mechanism,mineral aggregate gradation composition and particle size.Combined with the research results of the research group on the healing performance of the specimens after macro cracking by oven heating,the differences of the healing performances of the asphalt mixture under the two different heating methods of oven heating and microwave heating were analyzed.The results showed that microwave heating was more efficient than oven heating,which greatly shortened the heating time.The healing effects of the specimens heated by microwave under 700W for 160s were better than that of the specimen heated by oven under its best heating condition(60℃,8h).As an efficient and environmental-friendly heating method,microwave heating technology can make the asphalt pavement warm up rapidly.Before the structural damage of the pavement,the asphalt pavement can be heated and repaired by microwave to extend its service life.