Study On Preparation And Properties Of Mixture At Micro-surface Of Phase Change Temperature Control

China has entered the era of road maintenance,and a large number of service roads are facing great maintenance pressure.Micro-surfacing has many advantages such as open traffic,good economic benefits,low energy consumption,green environmental protection and so on,and is widely used in road maintenance at home and abroad.However,the pavement maintained by traditional micro-surfacing will still face many temperature-related diseases,such as cracking at low temperature,snow accumulation and freezing at low temperature in winter,which will affect driving safety and service performance.In order to improve the performance of pavement after maintenance at micro-surfacing,and reduce or eliminate diseases related to low temperature,this paper proposes to add phase change materials into micro-surfacing mixture,and study the influence of phase change materials on the performance of micro-surfacing mixture and the effect of temperature adjustment and deicing at micro-surfacing.In this paper,tetradecane,an organic solid-liquid phase change material with a phase change temperature of about 0℃,was selected as the main phase change material for anti-freezing ice.According to the properties of phase change materials and wrapping materials,the preparation technology of microencapsulated phase change materials for pavement at micro-surfacing was studied.Differential scanning calorimetry(DSC),thermogravimetry(TG)and scanning electron microscopy(SEM)tests were carried out on microencapsulated phase change materials from three aspects: properties,thermal stability and long-term stability.The final phase change starting temperature,peak phase change temperature,maximum weight loss temperature and latent heat of phase change are-0.46℃,-1.41℃,189.76℃ and 100.1J/g,respectively.The material meets the technical requirements of phase change materials for pavement temperature rise at micro-surface.The ratio of phase change micro-surfacing mixture was studied,and the dosage of cement,water,phase change material and asphalt-aggregate ratio of micro-surfacing mixture were determined by routine mixing test and cohesion test.According to 1h wet wheel wear test and sand adhesion test,the best oil-stone ratio of the mixture at the micro-surface of phase change is selected,and then the performance of the mixture at the micro-surface of phase change is studied by wet wheel wear test and wheel track deformation test.The test results show that the optimum oil-stone ratio of the mixture at the micro-surface of phase change is 7.2%;Adding 3% phase change material to micro-surfacing mixture can improve its water stability and anti-rutting ability,and its wear resistance can meet the specification requirements.In this paper,by simulating the wet and cold environment of the pavement at the micro-surface,the temperature adjustment effect test and ice melting test of the mixture at the micro-surface of phase change are carried out in a constant temperature control box.The test results show that the micro-surface of phase change has certain temperature adjustment ability and ice melting ability,which can reduce the cooling rate at the micro-surface and delay the time of reaching the low temperature extreme value,and the phase change temperature adjustment effect is good.