| Road ice and snow has become a serious threat to the traffic safety.The ice on the road usually cannot be removed even the snow was removed by using traditional "passive" removal technology.The traditional technology not only wastes a lot of manpower and material resources,but also causes certain harm to the road surface,infrastructure and environment.As an "active" removal technology,salt storage asphalt pavement has received more and more attention,in which the fine aggregate or mineral powder in the asphalt mixture was replaced by salt storage asphalt pavement additives.The snowmelt salt which actives snowmelt can be gradually precipitated to the road surface due to the vehicle load and capillary tube effect.In this paper,a powdered salt storage asphalt pavement additive was designed and developed.The salt storage asphalt slurry and mixture with the designed additive were obtained.The main research contents and conclusions are as follows:(1)Diatomite-sodium chloride core material(DN)was prepared by vacuum saturation method using diatomite and sodium chloride as storage carrier and snow melting salt,respectively.The core material was wrapped by wet grinding using phenolic resin-anhydrous ethanol to obtain a salt-storage asphalt pavement additive(DN-PF).The micromorphology,phase composition and infrared absorption characteristics of DN-PF were studied.The results indicated that diatomaceous earth can adsorb and carry sodium chloride well.The surface of the core material was successfully wrapped with a layer of phenolic resin shell.There is no chemical reaction during the adsorption wrapping process.(2)The technical performance of DN-PF was tested and evaluated by chloride ion content,heat resistance index,moisture absorption,sustained release performance,ice melting amount and other tests.The results showed that the chloride ion content of DNPF was 38.0% and the heat resistance index was 0.01%,which meet the requirements of powdered salt materials in the Standard(JT/T 1210.2-2018).DN-PF has a certain degree of hygroscopicity.In addition,the crushing of phenolic resin shell may help the precipitation of sodium chloride in the low temperature environment in winter,which lead to the obvious slow-release effect.The ice melting amount test showed that DN-PF have good ice melting and sustained release performance.(3)The salt storage bitumen slurry was prepared by replacing mineral powder with DN-PF.The micromorphology of asphalt slurry was analyzed by fluorescence microscopy.The basic physical properties of salt storage asphalt slurry were analyzed by penetration degree,ductility and softening point tests.DSR and BBR measurements were used to analyze the rheological property difference between the ordinary asphalt slurry and salt storage asphalt slurry at high and low temperature.The slow-release performance of salt storage slurry specimens was studied.The results show that the compatibility of DN-PF with SBS modified bitumen is better than that of matrix bitumen under the action of SBS cross-networked structure.The incorporation of DN-PF can increase the consistency of salt storage asphalt slurry and enhance the shear resistance.It will reduce the plasticity of salt storage asphalt slurry and deteriorate the crack resistance at low temperature.Furthermore,the incorporation of DN-PF can reduce the temperature sensitivity of the salt storage asphalt slurry.With the increasing temperature,the viscosity of salt storage asphalt slurry decreases,and the viscoelasticity and rutting resistance are enhanced compared with the ordinary asphalt slurry.With the decrease of temperature,the deterioration degree of salt storage asphalt slurry is much better than that of ordinary slurry.The slow-release performance of salt-storing asphalt pavement additives is further enhanced by the wrapping of asphalt film.(4)The salt storage asphalt mixture was prepared by DN-PF and other volumetric replacement ore powder.The road performance and ice melting properties were studied.The results showed that the incorporation of DN-PF improved its high temperature stability to a certain extent but would deteriorate the low temperature crack resistance and water stability.The salt storage asphalt mixture has a good effect on melting ice and snow,and can effectively reduce the adhesion between the ice layer and the asphalt pavement in the cold environment of winter.The precipitation rate of snowmelt salt of salt storage asphalt mixture is uniform,the precipitation amount is stable,with slow release effect and long-term effectiveness. |
