| At present,a huge amount of waste materials such as waste rubber and plastics and waste edible oil cannot be properly disposed of,which causes serious environmental pollution.Therefore,environmentally friendly and high-valuable disposals of them are urgently needed.The application of above waste materials in highway asphalt can not only obtain effective usage of them,but also improve the quality of highway.However,the crumb rubber and plastic are difficult to disperse and stabilize in hot asphalt,which leads to a poor storage stability of modified asphalt.Besides,low amount of crumb rubber and plastic,difficult processing and other problems also exist in crumb rubber or plastic modified asphalt.And the waste cooking oil seriously hinders the improvement of high temperature performance in the modification of pavement asphalt,which restricts the application and promotion of waste materials in modified asphalt.In order to enhance the high-valued treatment of the above waste materials and solve the problems of poor storage stability and insufficient comprehensive performance advantages of traditional single crumb rubber or plastic modified asphalt,the preparation and performance evaluation of composite modified asphalt with crumb rubber/plastic materials were carried out.Four kinds of crumb rubber/plastic composite modified asphalt were prepared by melt shear process,pyrolysis process,screw extrusion process and waste cooking oil desulfurization process.The basic properties(physical properties,construction performance,storage stability,economy,aging resistance,etc.)of 4 types of modified asphalts and the road performance of their asphalt mixtures were studied.Finally,the experimental road of the modified asphalt prepared with the most proper process was conducted to evaluate the application effect of it in the engineering.The findings obtained as follow:Firstly,the penetration,softening point,ductility at 5℃,elastic recovery,Brookfield viscosity and storage stability tests were used to study the physical properties,construction properties and storage stability of four kinds of composite modified asphalts.It was found that the high-temperature stability of the four kinds of composite modified asphalt was improved,and the elastic recovery capacity was more than 70%.The construction property of the modified asphalt obtained by waste cooking oil desulfurization process is poor,the viscosity at 135℃ of the other three kinds of modified asphalts is below 3000 m Pa·s,and the construction property of shear process is the best.Except for melt shear process,the modified asphalts obtained by other processes meet the requirements of storage stability specified in the specification.Then,the cost of raw materials required to prepare 4 kinds of composite modified asphalts was compared,and it was found that thermodynamic processes represented by high-temperature cracking process and waste cooking oil desulfurization process have higher economic efficiency.Among them,the modified asphalt prepared by high-temperature cracking process has a great application prospect because its excellent comprehensive performance,short processing cycle and no special equipment.Next,the short-term and long-term aging simulation tests at laboratory were conducted on the 4 types of composite modified asphalts.By comparing the physical performance indicators and viscosity indicators before and after aging,it is found that the 4 types of modified asphalts have excellent short-term and long-term aging resistance.Waste cooking oil desulfurized crumb rubber/SBS composite modified asphalt has the best aging resistance.From the perspective of softening point increment and residual viscosity ratio,screw extruded crumb rubber/PE modified asphalt shows the best long-term aging resistance performance.And short-term aging resistance of it is better than crumb rubber/PE modified asphalt,but there is a certain gap between it and high temperature cracked crumb rubber/PE modified asphalt.Finally,4 types of composite modified asphalt mixtures were mixed under the optimal ratios of oil and aggregate,and their road performance was evaluated.It was found that the rutting resistance of the composite modified asphalt mixtures was greatly improved,and the low-temperature crack resistance was significantly improved.Compared with SBS modified asphalt mixture,their water damage resistance and fatigue performance have obvious advantages.The storage stability of rubber-plastic composite modified asphalt prepared by melt shear process can be improved significantly by using anti-aging agent 264.Based on the research results,the experimental road was investigated using this kind of composite modified asphalt.It was found that the compact effect was good,and the service condition still maintains better after 5 years of pavement operation. |
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