Influence Of Temperature And Humidity Field On The Dielectric Properties Of Typical Distresses In Asphalt Pavement

When using non-destructive testing equipment for non-destructive testing of asphalt pavements,the engineering quality evaluation and distress identification of asphalt pavements are realized based on the difference in dielectric properties of distress in asphalt pavement.The dynamic change of temperature and humidity field in the service environment of asphalt pavement will affect the dielectric properties of asphalt pavement materials,thereby affecting the detection results of non-destructive testing equipment.Therefore,how to accurately evaluate the effect of temperature and humidity field on the dielectric properties of asphalt pavement materials is of great significance for improving the accuracy of non-destructive testing of asphalt pavements.In order to clarify the influence of temperature and humidity field on the dielectric properties of typical distresses in asphalt pavement,this paper theoretically established the influence model of temperature and humidity on the dielectric properties of asphalt mixture based on previous studies,proposed the equivalent conversion method of nondestructive testing data under different temperature,humidity and frequency conditions,and clarified the typical structure of asphalt pavement and the distribution law of the composite field of temperature and humidity at the location of the distress and its influence on the dielectric properties.The main conclusions obtained are as follows:(1)Temperature is an important factor affecting the dielectric properties of asphalt mixtures.In this paper,based on the analysis of the influence mechanism of temperature on the dielectric properties of asphalt mixtures,the theoretical relationship between the temperature factor and the relative permittivity of asphalt mixtures was constructed and verified,which proved that the theoretical model has strong applicability and can quantify the influence of temperature and humidity factors on the dielectric properties of the asphalt mixtures.(2)From a microscopic point of view,due to the limitation of covalent bonds and chain bonds,the polarization of asphalt is mainly electronic polarization,while the polarization of aggregates is mainly ionic polarization.The strength is higher than that of asphalt,so the relative dielectric constant and dielectric loss of aggregate is greater than that of asphalt.At the same time,there are obvious differences in the conductivity activation energy of different aggregates and asphalt,and the energy required for materials with large conductivity activation energy to change from a normal state to an active state that is prone to conduct electricity is larger,which also provides a new idea for the development of asphalt pavement snow melting technology from the perspective of material selection.(3)Humidity is an important factor affecting the dielectric properties of asphalt mixtures.In this paper,based on the study of the influence mechanism of humidity factors on the dielectric properties of asphalt mixtures,the theoretical relationship between humidity and relative permittivity was constructed and verified,indicating that the theoretical model has a certain general applicability and can quantify the influence of humidity factors on the dielectric properties of asphalt mixtures.(4)This paper established the temperature-humidity-frequency equivalent principle of relative permittivity of asphalt mixture through theoretical derivation,and designed the measurement test of relative permittivity of asphalt mixture under multiple temperature and humidity conditions to prove the reliability of the efficiency principle.At the same time,the temperature-humidity-frequency equivalent conversion method established in this paper has a certain scope of application,and it is suitable for the main temperature and humidity range of asphalt pavement service and the main frequency range of non-destructive testing of asphalt pavement,which can be used as a theoretical basis to realize the conversion of relative permittivity under different temperature,humidity and frequency conditions to a certain extent,and be used as the theoretical basis to realize the unification of testing data of non-destructive testing equipment.(5)This study established a model of the atmospheric temperature change rule in central China at every moment,and based on this,realized the COMSOL finite element simulation of the temperature field of three different typical asphalt pavement structures and proved the feasibility of the simulation results.On this basis,the temperature fields of the three different typical asphalt pavement structures,cracks,and cavities were simulated.The results showed that the temperature fields of the three different typical asphalt pavement structures were consistent.At the same time,it was proved that the distress in the asphalt pavement had not been if the air is in direct contact,the temperature field distribution is consistent with the normal asphalt pavement.If the distress in asphalt pavement is in direct contact with the air,the temperature field will form a big difference.Combined with the forward modeling results of cracks on the surface of asphalt pavement,it is found that the influence of temperature field on the dielectric properties of typical asphalt pavement lesions is of great significance for the quality evaluation and maintenance of asphalt pavement.(6)This study established a model of the variation law of atmospheric relative humidity in the central region of my country at each time,and the temperature and humidity field of typical asphalt pavement distresses was established based on the results of the asphalt pavement temperature field,which shows that top-down cracks and reflective cracks do affect the distribution of humidity field of asphalt pavement,where the moisture concentration at top-down cracks will be lower than that of normal asphalt pavement,while the mositure concentration at reflective cracks will be greater than normal asphalt pavement.This demonstrates that both that both top-down cracks and reflection cracks can provide channels for the movement of water and air inside the asphalt pavement.Meantime,the influence of the asphalt pavement temperature and humidity field on the dielectric properties of asphalt pavement materials was found greater than only considering the effect of the temperature field.The simulation results show that when the temperature and humidity field is considered,the relative permittivity of top-down cracks and reflection cracks is different from that of the normal road surface,which will interfere with the judgment and identification of the distress form by the non-destructive testing equipment,thereby affecting the detection accuracy of the non-destructive testing equipment.Combined with the forward modeling results of distresses on the surface of asphalt pavement,it is found that clarifying the influence of temperature and humidity field on the dielectric properties of typical asphalt pavement lesions has a positive effect on improving the accuracy of non-destructive testing of asphalt pavement and the accuracy of asphalt pavement distress identification,which can provide a reference basis for asphalt pavement quality evaluation and maintenance.