Research On Design And Performance Of UV-Irradiation Grafting Temperature-Sensitive Compound Snowmelt Filler

Snow and freezing on road in winter not only affect the traffic capacity,but also threaten the safety of vehicles and pedestrians,even causing casualties and property losses.Adding slow-release snowmelt agent into asphalt concrete is one of the common techniques to alleviate the problem of road snow freezing in winter.However,for the conventional slow-release salt-storage snowmelt asphalt concrete,a large amount of internal snowmelt agent is easy to precipitate in the summer high temperature rainy season,resulting in waste of snowmelt filler and adverse impact on the environment and infrastructure along the road.How to control the temperature-release of snowmelt agent has important academic and application value to improve the efficiency and environmental protection.Based on the surface modification principle of polymer,a temperature-sensitive slow-release snowmelt agent（TSSA）based on UV-irradiation grafting technology was proposed in this paper.The temperature sensitive materials were grafted onto the polymer film on the surface of carrier by UV-irradiation grafting technology.Based on the swelling and contraction characteristics of temperature-sensitive materials at different temperatures,the temperature-control of internal snowmelt agent precipitation was realized,and the temperature-sensitive slow-release salt-storage snowmelt asphalt pavement structure（AC-TSSA）was designed by adding the TSSA into the asphalt mixture.For preparing TSSA,the selection and proportion of raw materials were determined.Based on the slow-release and temperature-sensitive performance,C₂ was selected as the carrier,and material Z was added to enhance the adsorption capacity of the carrier and improve the performance of the mixture.The surface of the carrier was hydrophobic treated and coated with span-60 and polymer P.Material B and AAm were grafted onto the surface of the carrier by UV-irradiation grafting technology.The LCST of the polymer was determined to be about 25℃when the ratio of material B and AAm was 3:2.According to the determined raw materials and ratio,a kind of TSSA filler with excellent slow-release performance and controlled snowmelt precipitation according to temperature change was prepared.In order to study the characteristics and the change of road performance after adding TSSA,the indexes of TSSA filler and the road performance of AC-TSSA with different proportion of TSSA were analyzed.The design of AC-TSSA adopted the form of TSSA equal volume replacement of mineral powder.The road performance of AC-TSSA specimen before and after snowmelt agent precipitation was compared based on the change of voidage of the specimen,and the evaluation model of the longterm and shortterm road performance and structural voidage of AC-TSSA pavement was established.The results showed that compared with the control group,the penetration time of TSSA filler was increased by 42.2%,the freezing point of aqueous solution was decreased by 10.9%,and the precipitation amount of snowmelt agent before and after 25℃was significantly different,indicating that TSSA had excellent temperature-control and slow-release performance and freezing point drop ability.The void fraction of AC-TSSA specimens reached the maximum value when the soaking temperature was 60℃,increasing by 16.5%compared with that of 30℃,and the void fraction of AC-TSSA specimens was close to the final value of the target porosity on the 8th to 10th day of soaking,which was used to evaluate the long-term road performance of AC-TSSA.The results show that,compared with the control group,the dynamic stability,maximum flexural strain and residual stability of AC-TSSA decrease by 25.9%,31.5%and6.7%,respectively,while the Cantabro Test loss increases by 35.1%.Considering road performance and snowmelt agent content,75%of equal volume replacement mineral powder was determined as the best proportion of TSSA.Aiming at the adhesion of ice to road surface,the ability of inhibiting freezing and the precipitation amount of snowmelt agent,the performance and service life of AC-TSSA were evaluated by qualitative observation and quantitative analysis.The results showed that compared with the control group,the adhesion between AC-TSSA specimen and ice surface decreases by 70.1%,and the BPN value increases by 62.1%.In the low temperature rain fog environment,the surface of the specimen was not easy to form thin frost and dark ice.The conductivity test results show that the conductivity of AC-TSSA specimens decreases 24.1%and 12.1%at 40℃compared with 20℃,respectively.With the increase of soaking time,the conductivity growth rate（RCG）decreases gradually.On the 11th day of sample immersion,RCG value decreased by about 90%compared with that on the 1st day.Compared with the static soaking condition,the conductivity of soaking solution increased by 83.6%within 10h after applying wheel load,indicated that vehicle load can significantly accelerate the precipitation of snowmelt agent.The life expectancy of AC-TSSA was estimated by using the conductively-concentration standard curve method,and an equation for predicting the life expectancy of AC-TSSA was proposed based on the regional climate characteristics.Taking Nanjing of Jiangsu Province as an example,the service life of AC-TSSA was about 8 to 9years,which was about 30%higher than that of the control group,indicating that AC-TSSA had better snowmelt performance.AC-TSSA pavement structure was designed based on UV-irradiation grafting temperature-sensitive compound snowmelt agent（TSSA）.Combined with the temperature control characteristics of temperature-sensitive materials and the active thaw characteristics of snowmelt salt-storage pavement,the effect of intelligent release of snowmelt agent inside the road was endowed.It was helpful to improve the material waste and environmental damage caused by the precipitation of snowmelt agent in high temperature rainy season,and was expected to alleviate the influence of snow and freezing on pavement in winter.