Study On Conductive Characteristic And Application Of Conductive Asphalt Concrete

With the rapid development of pavement construction in China, the maintenanceand security of pavement has been attracting high attentions. As a result the researchon the judgment of maintenance time and snow melting in winter have become anincreasing concern in the field of bituminous materials all over the world. In recentyears, Conductive asphalt concrete (CAC) has received much attention with severaladvantages of piezo-resistance, electric heating and self-healing. At present, mostresearch about preparation and properties of CAC has been done in the laboratory,and it cannot provide guidance for applying them in engineering. Therefore, it is ofgreat significance to investigate the relationship of conductive characteristic,interfacial behavior, performance after ageing and construction technology of CAC.This will provide theoretical guidance for the popularization and application of CAC,thus enhancing the durability of pavement.In the view of these, the change regularity with different press, temperature andhumidness was shown by the study which researched on the effects of raw materialsand environmental conditions on conductive characteristic. The interfacial behaviorof conductive asphalt binder was studied with X-ray fluorescence analysis (XRF),scanning electron microscope (SEM), X-ray diffraction analysis (XRD), Fouriertransform infrared spectroscopy (FTIR), ultraviolet-visible spectrum (UV-Vis) andcontact angle measurement. Electrical properties and pavement performance wereinvestigated after ageing by short time oven aging (STOA) and longtime oven aging(LTOA). Ageing attenuation model was established. According to equipment in theconstruction site, mixing, transportation, pave method and compaction were defined.The performance of CAC pavement was tested nearly2years. The main conclusionsare as follows:(1) In order to get good conductive characteristic, the aspect ratio of individualaggregate should be less than2:1and eccentricities of individual aggregate is lessthan0.78. The Superpave and AC gradation has good voids and connectivity.Furthermore, the surface distance of fake graphite is related to void in mineralaggregate (VMA), voids (VV), volume content and particle size of graphite, thus theresistance model of CAC was established. (2) When constant force or variable force applied on the CAC, resistance creepand piezo-resistance appear. So piezoresistive effect is not only about conductive path,but it is also about interfacial effect and micro cracks.(3) The resistance of CAC has temperature and humidity effect with differentenvironment and increases irreversibly. This illustrates the resistance of CAC not onlyreflect the internal fatigue damage, but also increases irreversibly according to thelocal climate conditions after paving.(4) Flake graphite surface has much of mesoporous, it caused specific area toincrease. Therefore, bitumen form the developmental adsorption film on the surfaceof flake graphite. The adhesion work between bitumen and graphite increase with riseof bitumen temperature. Flake graphite absorb heat first and then gives off heat whenmixing.(5) Graphite-bitumen dispersed system is a loosened accumulation system. Thus,the resistance of CAC is resistance between two graphite particles. In addition, Zetapotential of flake graphite is positive value in the acid environment, which indicatesconductive network of graphite-bitumen system a relatively stable system.(6) Compare CAC and common asphalt concrete after STOA or LTOA, thepavement performance is close. The electrical properties of CAC reduce from top tobottom of specimen. The ageing attenuation model of pavement and electricalproperties of CAC was established at135℃according to the time temperatureequivalence principle.(7) On the basis of established mixing model, added technology of graphite was putforward. The mixing process was defined. The construction key parameters of paverand compaction equipment were determined. The CAC road has good pavement andelectrical properties while meeting the requirements of the application inself-monitoring, snowmelt deicing and self-healing.