Study On The Temperature Changing Performance And Road Performance Of Thermochromic Sand Mist Sealant

Black asphalt pavement absorbs solar radiation and stores heat,which makes it prone to high temperature diseases in summer and aggravates the urban "heat island effect".Thermochromic powder is a thermochromic material,which can dynamically change its color according to the ambient temperature and has good light reflection ability after the color change,and is used in garment,ink and paint industries.There have been studies that show that the mixing of heat-changing powder asphalt binder and asphalt mixture have a significant cooling effect,however,the amount of powder required is high,and different varieties of powder on the technical performance of asphalt and the road performance of the mixture has a different impact law.Emulsified asphalt has a wide range of applications in asphalt pavement maintenance technology,from the cooling principle of thermochromic powder on the pavement and the optimal amount of consideration,the application of thermochromic powder in emulsified asphalt has a wider applicability and better economy.Therefore,in this paper,a thermochromic emulsified asphalt is prepared,and the effects of different dosing and color types on its technical performance are analyzed.After that,the thermochromic emulsified asphalt is combined with sand fog seal technology to study the road performance and temperature change characteristics of thermochromic sand fog seal.Firstly,three kinds of powders,RTP(red thermochromic powder),BTP(blue thermochromic powder)and HTP(black thermochromic powder)were used to prepare thermochromic emulsified asphalt,and the effects of powder admixture and color type on the conventional technical properties,segregation,60℃ dynamic viscosity,viscoelastic properties,high temperature performance and low temperature performance of emulsified asphalt were analyzed to determine the significance of each The significance of each influencing factor was determined based on the results of ANOVA.The results show that the three thermochromic powders have the same effect on the technical properties of emulsified asphalt,all of them can increase the consistency and hardness of the evaporated residue,reduce the needle penetration and ductility,increase the dynamic viscosity and softening point.The powder reduces the plastic deformation resistance of the evaporated residue,increases the sensitivity of the nonrecoverable creep flexibility of the evaporated residue to heavy loads,and improves the high temperature performance.It also reduces the creep rate of evaporated residue,increases creep stiffness,and reduces low temperature crack resistance.The segregation phenomenon of emulsified asphalt will become more obvious with the increase of powder dosing.Secondly,thermochromic emulsified asphalt was prepared as a fog seal layer containing sand,and the effects of different dosing and color types of powder on the road performance of the fog seal layer containing sand were investigated through interlayer adhesion test,water penetration performance test,anti-slip performance test and anti-abrasion performance test.The results show that the amount and color type of the thermochromic powder do not have any significant effect on the road performance of the fog seal layer with sand.Thirdly,an indoor simulated light system was set up in the laboratory to perform light cycle tests on asphalt mixture specimens sprayed with a thermochromic sand-containing fog sealer.In order to confirm the actual cooling effect of the thermochromic fog sealer on the asphalt pavement in the hot summer,the specimens were placed outside for natural light cycle tests.The results showed that the thermochromic sand fog sealer showed good cooling effect in the indoor simulated light test,and the maximum temperature reduction compared with the blank group occurred at the depth of 2cm,and the maximum temperature reduction was 4.0℃when the powder dosing was 8%.The larger the powder doping,the lower the heating rate of the specimen and the larger the temperature gradient value.As the number of light exposure increased,the heating rate of the thermochromic sand-containing fog seal layer increased,but the cooling amplitude did not show significant changes.In the outdoor cyclic light test,the cooling rate of the specimens at 2 cm depth was up to 2.8°C.In general,the cooling effect of RTP was better than that of BTP and HTP,and all specimens showed good temperature change durability in the short term.Finally,in order to explain why different colors of thermochromic powders have different cooling effects on the sand-containing fog seal layer,light reflectance tests were conducted on the thermochromic powder and thermodynamic tests were conducted on the thermochromic sand-containing fog seal layer,respectively.The results show that the thermal conductivity of the thermochromic sand-containing fog sealer is smaller and the heat capacity is larger than that of the blank group,and the reflectivity of RTP in the natural light and infrared light bands is better than that of the other two colors of powder.