Research On Self-healing Properties Of Asphalt And Asphalt Mixtures

In this paper,the induction heating and microwave heating were applied respectively to prepare self-healing asphalt mixtures.The “filler exothermic self-healing asphalt mixture” which stimulates the filler to provide heat was prepared.“Aggregate heated self-healing asphalt mixture” which stimulates the aggregate to provide heat was also proposed and prepared in this study.The self-healing properties of those two kinds of self-healing asphalt mixtures were measured and compared.The results showed that the self-healing asphalt mixtures can restore the mechanical strength of the asphalt mixture to more than 80% in a short time under the appropriate heat-induced self-healing technologies.According to the current research situation of self-healing asphalt mixture,the self-healing characteristic researches of asphalt and asphalt mixtures under different service levels and service conditions were conducted,including UV aging,mechanical fatigue,freeze-thaw cycle,snow and ice melting and so on.As a consequence of the changing trend analyze of different influencing factors of asphalt and asphalt mixture,this paper also put forward the asphalt road self-healing maintenance timing judgement and timing options.The main conclusions of this paper are as follows:1.The influence of different UV aging time on self-healing properties of matrix asphalt was studied by Dynamic Shear Rheometer and Fourier Transform Infrared Spectroscopy.The results showed that the asphalt flow behavior curve obtained by the Dynamic Shear Rheometer can reflect the relationship between the flow properties of the asphalt and the temperature.The flow properties and self-healing properties of the asphalt will decrease with the continuous aging of the asphalt.The time when the asphalt flow behavior curve is permanently below the key value of 0.9will be the cut-off point of the timing of the curing of the matrix asphalt;2.Different service conditions would result in different self-healing performances of asphalt pavement: The self-healing recovery of asphalt mixture willdecrease with the increase of mechanical fatigue.After several times of mechanical fatigue fractures,the two kinds of self-healing asphalt mixtures designed in this paper can still maintain the mechanical strength to more than 50%;the existence of rainwater can improve the thermal conductivity and heat-generating properties of asphalt mixture to a certain extent,but the moisture will greatly hinder the self-healing process of asphalt,which leads to the temporary loss of self-healing characteristics of asphalt.With the flow and evaporation of water,asphalt material will gradually restore its self-healing properties;3.Under the special winter conditions(such as snow and ice melting or freeze-thaw environment),the asphalt mixture will be affected by the infiltration of water and other moisture damages,as well as faced some structural damages caused by the volume expansion effect while the water turned into ice.The existence of moisture will lead to the decrease of self-healing efficiency of asphalt road from about 80% to 20%.The results also showed that the two heat-induced self-healing techniques had a very significant acceleration effect and practical application potential in snow and ice melt,the highest average melting rate of self-healing asphalt mixture could reach at 53.9g/min in this paper;4.The results of molecular dynamics simulation and fluorescence microscopic analysis showed that the wetting effect between the interface of asphalt materials is a prerequisite for the self-healing behavior of asphalt materials.The presence of free moisture not only greatly prolongs the time required for self-healing of the asphalt material,but also the residual moisture can lead to incomplete contact and healing of the asphalt fracture interface,and finally affect the result of self-healing performances;5.Compared with induction heating technology,the self-healing asphalt mixture under the microwave technology has a wider range of self-healing effect,and the effect is more uniform,which helps to avoid the local overheating and the temperature stress of the asphalt mixture during the self-healing process.6.In order to ensure the good healing performance with heat-induced self-healing techniques,it is recommended that the recommend process should be applied with warm and dry period of asphalt pavement.It is better to heal the asphalt pavement before the frozen damage occurred in winter.The self-healing process ofasphalt mixtures is not suggested when it's right after the rain or snow.