| Asphalt binder has a high solar radiation absorbability,which might elevate the temperature of asphalt pavement,and damages the pavement durability,driving safety and urban Eco-environment.Phase change material(PCM)can absorb heat during the phase change process and its temperature can remain constant,which can be used for temperature control of asphalt pavement.In this paper,the heat transfer features of asphalt pavement with PCMs were first investigated,and the cortresponding finite element models(FEM)were established.Based on the FEM results,the selection criteria of PCMs for asphalt pavement temperature control were also determined.Afterwards,a series of shape-formed expanded graphite(EG)/polyethylene glycol(PEG)composite phase change materials(EPs)were prepared.Finally,the influence of EPs on the temperature control and service performance of asphalt binder and asphalt mixture were studied.The maintain conclusions are as follows:(1)The heat transfer features and finite element model of asphalt pavement temperature field with PCMs were studied.Besides,the selection criteria of PCMs for asphalt pavement temperature control were determined.When the PCMs with the phase transition temperature of 43?C,34?C and 30?C were separately incorporated to the upper,middle and bottom layer of asphalt pavement with the dosage of 2.5%,the temperature of asphalt pavement surface layer could be reduced by 5?C compared to the ordinary asphalt pavement,and the time that the highest temperature appears has been postponed for at least 1.7h.(2)When the PEGs with the molecular weight of 1500 and 1000 were selected,the phase transition temperatures of the prepared EPs were 42.67°C and 30.18°C,respectively.And the latent heats were 122.94J/g and 121.89J/g while the thermal conductivities were 3.5202W/m·K and 3.5141W/m·K,and the EPs could meet the criteria for asphalt pavement temperature control.The mass loss of EPs were less than 3.0% at 200?C,and the mass loss at 330?C were no more than 10%,the phase transition properties of EPs could remain stable after 50-time temperature cycles.These results indicated that the EPs were able to survive during the production and service process of asphalt mixture for excellent thermal stability and durability.(3)Incorporating EPs reduced the heating and cooling rate as well as extended the heating and cooling time of asphalt binders,which proved the temperature-control effects of EPs.EPs doubled the thermal conductivity of asphalt binder,and enhanced the binders’ thermal storage capacity.EPs improved the binder’s rheological properties at high-temperature,but had impact on the middle and low temperature rheological performance.The storage stability of EPs to asphalt binders was favorable,and the workability of asphalt mixture was damaged for incorporating EPs.(4)The heating and cooling rate of asphalt mixtures were separately reduced at the temperature range of 40?C-50?C and 35?C-25?C because of the phase transition of EPs.The highest temperatures of the upper,middle and bottom layer of asphalt pavement with the EPs dosage of 2.5% were reduced by 3.7?C,3.9?C and 3.9?C,respectively,which indicated that EPs were conductive to temperature regulation,and the simulating accuracy was satisfactory.Incorporating EPs improved the rutting resistance of asphalt pavement,and the fatigue resistance,low-temperature cracking resistance and water stability were slightly reduced,but still met the requirements of road performance. |
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