Study On Preparation Of Form-stable Composite Phase Change Material And Its Influence On Asphalt Mixture Performance

Asphalt pavement is widely used in the construction of modern high-grade highways due to its unique advantages.However,under the action of continuous high temperature climate,various thermal stability diseases caused by asphalt pavement will affect traffic safety,pavement maintenance management and road service life,etc.This has had a serious impact.Based on the principle of phase change heat storage,this paper uses different synthesis processes to prepare two form-stable composite phase change materials?FSPCMs?,and add them to the asphalt mixture to reduce the temperature rise rate and peak temperature of the asphalt pavement at high temperatures.Firstly,according to the technical requirements of phase change materials?PCMs?suitable for cooling asphalt pavements,polyethylene glycol?PEG?with suitable phase transition temperature,large phase transition enthalpy and good thermal stability is selected as PCMs.The peak melting temperature of PEG is 51.12?,the melting enthalpy is 185.6J/g,and it has good thermal stability below 385?,and can be applied to asphalt pavement for heat storage and cooling.Secondly,in view of the shortcomings of PEG,such as easy leakage and low thermal conductivity,silica?Si O₂?is selected as the carrier matrix,and PEG/Si O₂FSPCMs are prepared by the sol-gel method,and SEM,XRD,DSC,TGA and the thermal conductivity test and other test methods study the surface morphology,crystallization performance,heat storage performance,thermal stability and thermal conductivity of composite materials.The test results show that Si O₂ as a carrier matrix can effectively adsorb PEG.The maximum adsorption capacity of PEG is 70%and the shaping effect is good.There is no liquid phase leakage after multiple phase change cycles,the composite material has a melting enthalpy of 97.53J/g,the thermal stability is good,and the thermal conductivity is also significantly improved.Then,using expanded graphite?EG?as the carrier matrix and Si O₂ as the encapsulating material,the PEG/EG/Si O₂ FSPCMs was prepared by the vacuum adsorption method and the sol-gel method,and the performance test and structural characterization were performed.The test results show that EG as a carrier matrix has a strong adsorption and shaping effect on PEG.The maximum content of PEG in the composite material is 82%,and there is no leakage after multiple phase change cycles.At the same time,the melting enthalpy of the composite material is as high as 136.7J/g,and the thermal stability and thermal conductivity have been further improved.Finally,two phase change particles,PEG/Si O₂ and PEG/EG/Si O₂,were added to the hot-mix asphalt mixture to prepare two phase change asphalt mixtures,and their cooling performance and road performance were tested.The results show that the phase change particles added to the asphalt mixture can still exert its phase change heat storage characteristics and reduce the heating rate of the asphalt mixture.The maximum cooling range of PEG/Si O₂ and PEG/EG/Si O₂ phase change asphalt mixture specimens is 2.2?and 2.9?respectively,which has a good inhibitory effect on high temperature diseases of asphalt pavement.Phase change asphalt mixture has good low-temperature crack resistance and water stability,but its high-temperature stability needs further study.