Research On Durability Of MCR Modified Asphalt Mixture In High Altitude And Seasonally Frozen Areas

The seasonal permafrost regions with high altitudes are widely distributed in China and have special natural environmental characteristics.High altitude,thin air,strong ultraviolet radiation,long sunshine time,large diurnal temperature difference,large heat and cold disparity,and complex and diverse climate environment coupled with heavy vehicle load accelerate the development of early diseases such as pavement cracks,pits and spalling,which seriously affect the performance and life of asphalt pavement.The durability of conventional asphalt mixture is poor,and it is difficult to meet the requirements of road use and use under continuous harsh environmental conditions.The new dry direct casting process rubber asphalt mixture based on Modified Crumb Rubber(MCR)has been proved to have obvious advantages over ordinary asphalt mixture in the previous study of conventional engineering environment.In order to demonstrate the application effect of the new dry process under the influence of harsh working conditions,this paper discusses the durability research and application of MCR modified asphalt in high-altitude seasonal frozen area.The significance of this study is to further improve the research system of dry process MCR modified asphalt technology,and play a positive role in promoting the application and promotion of MCR modified asphalt mixture in high-altitude seasonal frozen areas,realizing energy conservation and emission reduction,green environmental protection,and promoting the sustainable development of road engineering construction.Firstly,the indoor simulation test scheme of ultraviolet aging and freeze-thaw cycle is designed.The indoor simulated ultraviolet aging box was made by introducing UV integrated curing lamp.Through the investigation of ultraviolet radiation intensity in Xinjiang area,and the ultraviolet intensity of indoor simulation test was converted to establish the indoor and outdoor ultraviolet irradiation time control.Based on the research results of previous freeze-thaw cycle test methods,and combined with the characteristics of local temperature distribution in Xinjiang,the number of freeze-thaw cycles and test methods were designed.The indoor asphalt performance test was carried out after environmental simulation.According to the three major indicators of asphalt,elastic recovery and rotational viscosity performance test results,combined with the corresponding preparation process conditions,construction and ease of use and engineering economy,it is determined that in the application of high altitude seasonal frozen soil modified asphalt with MCR,the rubber powder content should be preferred about 17.5 % and not less than 15.0 %,which can take into account all aspects of modified asphalt.After that,in the conventional performance index,SHRP index and four-component analysis test of asphalt,it is demonstrated that after the ultraviolet and freeze-thaw conditions,the performance of MCR modified asphalt is significantly better than that of ordinary rubber asphalt and SBS modified asphalt.The comprehensive ranking of road use and durability is as follows : MCR modified asphalt > ordinary rubber asphalt > SBS modified asphalt.Compared with the other two kinds of modified asphalt,the test results show that the modified asphalt with MCR has better applicability in high altitude seasonal frozen area.Then,based on the raw materials of Xinjiang Wuyu highway project construction site,the Marshall design method is used to determine the AC-16 C asphalt mixture gradation,MCR modified asphalt and other three kinds of conventional modified asphalt mixture.The durability of the mixture was comprehensively evaluated by asphalt adhesion test,high temperature stability test,low temperature crack resistance test,water stability test and fatigue performance test.The test results show that compared with SBS modified asphalt,ordinary wet rubber asphalt and ordinary dry rubber asphalt mixture,the performance degradation of MCR modified asphalt mixture is the slowest and the durability advantage is obvious under the adverse environmental conditions of ultraviolet and freeze-thaw.It can be preferred in the construction of high-grade highways in areas with strong ultraviolet at high altitude and frequent freeze-thaw.Finally,the entity engineering verification and tracking observation are carried out based on the surface engineering project of Yiruo line in Xinjiang.The results show that the asphalt pavement condition of MCR after 3 months and 6 months of service is significantly better than that of SBS modified asphalt pavement in the same period.The construction technology of dry direct casting process of MCR modified asphalt mixture is simple,and the economic and social benefits are remarkable.The application of dry direct casting process in highway construction in high altitude seasonal frozen area can improve the pavement and performance of asphalt pavement,prolong the road life cycle,and save direct and indirect costs.