| Because of its characteristics of energy storage and temperature control,phase change materials(PCMs)can reduce the peak temperature of the asphalt pavement at high temperatures,thereby improving the anti-rutting performance of asphalt pavement.However,it often has problems such as easy leakage of PCMs and degradation of asphalt performance when PCMs applied in asphalt directly,in order to avoid such problems,this thesis mainly studies the microencapsulation of PCMs.By coating the surface of the PCMs with a shell,the working environment of the PCMs can be separated from the actual application environment,thereby improving the efficiency of PCMs used in asphalt.Asphalt pavements are prone to rutting in high temperatures during the summer,and due to the high endothermic capacity of bituminous materials,urban roads absorb large amounts of heat at high temperatures and store them,exacerbating the urban heat island effect.In order to alleviate the urban heat island effect and reduce the occurrence of high-temperature rut on asphalt pavement,it is a feasible solution to study the temperature-reduction technology of asphalt pavement and seek an active and effective temperature control method for asphalt road.Phase-change temperature-controlled pavement technology is an effective method for temperature control of asphalt roads.The PCMs applied in asphalt directly often has problems such as easy leakage of PCMs and degradation of asphalt performance,in order to avoid such problems,this thesis considers the microencapsulation of phase change materials.By coating the surface of the PCMs with a shell,the working environment of the PCMs can be separated from the actual application environment,thereby improving the efficiency of phase transition materials used in asphalt.With hexadecanoic acid as the core material and melamine resin as the wall material,microcapsules were prepared by in-situ polymerization in this thesis.Single factor analysis was used to investigate the influence of the ratio of core wall mass,emulsifier concentration,synthesis stirring rate and synthesis temperature on the microcapsule enthalpy and average particle size.Based on the influence law under single factor conditions,an orthogonal test was designed.The test results confirmed that the best preparation process of hexadecanoic acid-melamine resin microcapsules is: core wall mass ratio 1:0.75,emulsifier concentration 10%,the synthesis stirring speed is taken as 500r/min and the synthesis temperature is set as 65°C.The order of the factors for the phase change enthalpy of the microcapsules is: core wall ratio> synthesis temperature> emulsifier concentration > synthesis stirring rate.SEM,DSC,TG,FTIR and laser particle size analyzers were used to analyze the microstructure,phase change behavior,heat resistance and structural composition of the formed microcapsules under the optimal preparation conditions.The test results show that the melamine resin is completely coated with hexadecanoic acid,and the prepared microcapsules have good heat resistance,stable phase transformation behavior,a coating rate of 59.51%,and microcapsules have smooth surface,full particles.With hexadecanoic acid and micro PCMs as modifiers,two types of phase change modified asphalt with different contents were prepared.The three indexes of two types of modified asphalts with different contents were tested,and the dynamic rheological properties of the two types of modified asphalts were analyzed with a dynamic shear rheometer(DSR).The results showed that with the hexadecanoic acid modified asphalt directly,the ability of the asphalt to resist deformation at high temperatures is reduced.The directly mix of the PCMs has an adverse effect on the high-temperature rutting resistance of the asphalt;When the asphalt is modified by the form of phase change microcapsules,the ability of the microcapsulated modified asphalt to resist permanent deformation is improved,and the addition of the micro PCMs can improve the high-temperature anti-rutting ability of the asphalt material. |
PDF Full Text Request