Properties Investigation Of Thermal Conductive Asphalt Mixtures

A black asphalt pavement can be considered to be an enormous solar collector due to its excellent heating-absorption property. The energy collected form asphalt pavements can be used for snow-melting and for cooling and heating of adjacent buildings. As a result, it can abate the use of fossil fuel in heating buildings and reduce the CO₂ emission. Because of the obvious benefits, asphalt solar collectors are becoming a new way of harnessing solar energy. Interest in such an asphalt collector is mainly focused on the energy potential and the thermal efficiency under our country's climate. It's known to all that it can enhance the thermal efficiency due to higher thermal conductivity and lower heat radiation loss. The aim of this paper is to produce thermal conductive asphalt solar collector by adding different thermal conductive fillers so as to improve the thermal efficiency. And then a finite element model was simulated to predict the temperature distribution of conductive asphalt pavement. It is supposed to be the base for the evaluation of energy potential of conductive asphalt pavement.Firstly, the effects of conductive fillers on the rheological properties of asphalt binders were taken into consideration. The results indicate that a proper addition of graphite can lead a lower penetration and temperature sensitivity, but a higher softening point and viscosity. The complex modulus is increased while the phase angel is decreased.Secondly, the effects of thermal fillers on thermal properties of asphalt mixtures were measured by transient plant source method. The results show that the addition of graphite can greatly improve the thermal conductivity. But there is no further improvement due to the addition of carbon fibers.Thirdly, a transient, two-dimensional model was simulated by finite element method, so as to predict the temperature distribution of conductive asphalt pavement. The results present that after the graphite was mixed in to the asphalt mixtures, asphalt pavement are with accelerated temperature changing rate and lower temperature gradient. And compared with normal pavement, the temperature at 10cm depth of conductive asphalt can increase by 3.4℃.Fourthly, the effects of thermal conductive fillers on the dynamic modulus and pavement properties of asphalt mixtures were investigated. The results illustrate that with an increasing addition of graphite, the dynamic modulus presents an increase trend and the phase angle decreases at lower temperature. The indirect tensile strength is greatly weakened by the addition of graphite. But carbon fibers play a positive role in supporting the strength. The permanent deformation can be greatly improved by the addition of graphite and carbon fibers. The addition of graphite can improve the fatigue properties of asphalt mixtures and carbon fibers cause a further improvement.At the end, the suggestion is that it's better for conductive asphalt solar collector to use graphite and carbon fibers as conductive filler and the dosage of graphite is no more than 18%.