Research On Thermal Induced Self-healing Performance Of Asphalt And Asphalt Mixture

Pavement cracks are the main damage form of asphalt pavement,which has an adverse effect on the performance of asphalt pavement.As a typical viscoelastic material,asphalt can repair its own damage,and use asphalt self-healing properties to extend the service life of asphalt pavement.Microwave heat-induced self-healing technology is currently a hot spot in the field of asphalt self-healing at home and abroad.This article mainly studies the microwave heat-induced self-healing characteristics of asphalt and asphalt mixtures,and comprehensively evaluates the feasibility and advantages of steel slag powder as a microwave absorbing material in the field of microwave heat-induced self-healing technology.First,two asphalts,steel slag powder and slag powder,are prepared For mortar,the microwave heating and self-healing characteristics of the two asphalt mortars were analyzed through microwave heating test and DSR test.Secondly,steel slag powder was used to replace part of the slag powder in the mixture gradation to prepare asphalt mixtures with different steel slag powder content.The self-healing effect of the microwave-induced asphalt mixture was analyzed through the semicircular bending test,and the orthogonal test was designed to analyze the influence of thermal induction factors on the healing index.Based on the acoustic emission,the fracture performance of the asphalt mixture was characterized and a new self-healing evaluation index was proposed.Finally,the influence of steel slag powder on the road performance of asphalt mixture was verified.The main conclusions obtained through the above research are as follows:Under microwave radiation,the steel slag asphalt mortar with a powder-to-binder ratio of 0.6,0.9,1.2 increased from 30.1℃to 67.4℃,88.2℃,and 103.8℃,respectively.The temperature of the slag asphalt mortar hardly changed with the microwave heating time,and the steel slag powder Due to the higher complex permittivity and complex permeability,more microwave energy can be converted into heat release,which ultimately leads to rapid heating,the microwave absorption capacity of limestone ore powder is limited,and the heat release is slow.The self-healing characteristics of the two asphalt mortars are characterized by the DSR frequency and temperature scanning mode.The study shows that with the increase of the powder-to-binder ratio,the flow behavior index of the mortar gradually decreases,and the modulus and viscosity increase.The initial temperature of self-healing of glue is in the range of 45℃～60℃,and the initial temperature gradually increases with the increase of the powder-to-rubber ratio.The fatigue-healing-fatigue loading test was performed on the two asphalt mortars through time scanning mode,and it was found that the healing index decreased with the increase of the powder-to-binder ratio,and the steel slag mortar had a better healing rate than the mineral powder mortar.With the increase of the healing temperature and the extension of the healing time,the healing index of the asphalt mortar increases firstly and then slowly.The healing condition corresponding to HI=0.9 is used as the best healing condition to obtain the best healing temperature and the best healing time of the asphalt mortar.The best healing time.Steel slag powder was used to replace part of the mineral powder in the gradation to prepare asphalt mixtures with different steel slag powder content.The semicircular asphalt mixture specimens were subjected to fracture-heal-re-fracture tests.The fracture specimens were healed by microwave heat induction,and the test was performed before and after healing.The ratio of the maximum breaking force of the piece is the healing rate.The healing rate increases with the increase of the replacement amount of steel slag.The growth trend is first fast and then slow.The addition of steel slag powder can increase the healing rate of ordinary asphalt mixture by 30%.The temperature distribution of the original asphalt mixture under microwave radiation is uneven,and there is a phenomenon of temperature concentration.The addition of steel slag powder makes the overall temperature of the specimen uniform,and the microwave heat-induced self-healing effect is better.Finally,it is comprehensively selected from the two aspects of healing effect and economy.The optimal replacement amount of Dinggang slag powder is 60%.Orthogonal experiments were designed to study the influence of microwave heat-induced conditions on the healing index of asphalt mixture.The order of influence is:microwave heating time>specimen damage degree>normal temperature curing time.At the same time,as the number of fracture damage increases,the strength of the asphalt mixture gradually decreases,and the healing rate is generally decreasing.The steel slag asphalt mixture shows a greater advantage,and its healing rate can still maintain about50%after multiple mechanical damages.The AE signal of the specimen fracture is detected by the acoustic emission system to detect the cracking healing process of asphalt.The asphalt mixture specimen exhibits brittle fracture characteristics at low temperature,and the values of various acoustic emission parameters are greater than normal temperature.During the fracture process of the specimen,as the load continues Increase,the acoustic emission signal continues to increase until the specimen is completely destroyed,and acoustic emission can well determine the failure process of the specimen.According to the cumulative energy curve,it shows that the strength of the asphalt mixture after healing has been restored to a certain extent.Finally,a new self-healing index HI_AE is proposed based on the acoustic emission energy parameters to characterize the healing characteristics of the material,and compared with the conventional indicators,it has a good Correlation.Rutting test,low temperature trabecular bending test,water immersion Marshall test and freeze-thaw splitting test are used to verify the conventional road performance of steel slag asphalt mixture.The addition of steel slag increases the modulus of asphalt mortar and improves the resistance of asphalt mixture.Rutting ability has no adverse effect on its water stability and low temperature performance.