Research On Design And Performance Of Warm-mix Flame Retardant Rubber Modified Asphalt And Its Mixture Used In Tunnel

Rubber asphalt mixture used in tunnel on the one hand can improve the performance of tunnel pavement,on the other hand can also consume a lot of waste tires,which has significant practical value and environmental protection significance.However,the construction temperature of rubber asphalt mixture is high,and the smoke generated is not easy to discharge in the semi-closed space of the tunnel,which greatly endangers the health of construction personnel.At the same time,traffic accidents in the tunnel can easily cause the burning of rubber asphalt pavement,high temperature and toxic smoke are difficult to discharge,which can easily cause serious casualties and property losses.Therefore,the rubber asphalt mixture needs to have both warm mix and flame retardant effects to facilitate its application in the special environment of tunnel engineering.In view of this,this paper designs warm mix flame retardant rubber asphalt and its mixture,and evaluates its warm mix,flame retardant and road performance,in order to provide a basis for the popularization and application of rubber asphalt mixture in tunnel pavement.Firstly,warm mix rubber asphalt was prepared by S-type and R-type warm mix agents,and the appropriate dosage of the two warm mix agents was determined by penetration,softening point and ductility tests.The warm mix effect of two warm mix agents was evaluated by viscosity and variable temperature compaction test.The dynamic shear rheological test(DSR),bending beam rheological test(BBR)and surface energy test were used to evaluate the effects of two warm mixes on the road performance of rubber asphalt.Based on the performance balance method,the warm mix agent suitable for rubber asphalt was determined.The results show that both S-type and R-type warm mix agents can significantly reduce the compaction temperature of rubber asphalt mixture.The S-type warm mix agent can greatly improve the high temperature and fatigue performance of rubber asphalt,but it will significantly deteriorate its low temperature performance and adhesion.The R-type warm mix agent can improve the low temperature performance and adhesion of rubber asphalt,but have a certain adverse effect on the high temperature and fatigue performance of rubber asphalt.Based on the warm mix effect of the two warm mix agents and their influence on the road performance of rubber asphalt,the R type warm mix agent is recommended as the warm mix agent of rubber asphalt.Secondly,the OA compound flame retardant was designed.The effect of OA compound flame retardant on the flame retardancy of warm mix rubber asphalt was studied by oxygen index test,and compared with the flame retardant of mineral powder,commercial ZK flame retardant and aluminum hydroxide(ATH).The effects of compound flame retardant on the physical rheological properties of warm mix rubber asphalt were studied by penetration,softening point,ductility,DSR and BBR tests,and the suitable content of OA compound flame retardant was proposed.The interaction between OA compound flame retardant and warm mix rubber asphalt was studied by Fourier transform infrared spectroscopy(FTIR).The results show that the flame retardancy efficiency of OA compound flame retardant is much higher than that of mineral powder,ZK flame retardant and ATH.When the content is 20wt%,the oxygen index of warm mix rubber asphalt can be increased to 25.1%.The OA compound flame retardant can significantly improve the high temperature and fatigue properties of warm mix rubber asphalt,and has a good synergistic effect with R type warm mix agent.Based on the comprehensive evaluation of flame retardant and physical rheological properties,the optimum ratio of OA compound flame retardant is recommended as 4wt% OMMT +16wt% ATH.The FTIR results show that there is a physical blending between OA compound flame retardant and warm mix rubber asphalt,and its effect on the flame retardant and physical rheological properties of warm mix rubber asphalt is determined by its own special properties.Finally,considering the high viscosity characteristics of rubber asphalt and the large amount of flame retardant,the preparation process of warm mix flame retardant rubber asphalt mixture was studied.The flame retardant and road performance of warm mix flame retardant rubber asphalt mixture under different preparation processes(dry and wet preparation processes)were evaluated by combustion test,high temperature rutting test,low temperature bending test,immersion Marshall test and freeze-thaw splitting test.The results show that the flame retardant performance and high temperature stability of warm-mix flame retardant rubber asphalt mixture prepared by dry process are similar to those of warm-mix flame retardant rubber asphalt mixture prepared by wet process,but the low temperature crack resistance and water stability are better.Therefore,it is more suitable to replace mineral powder with OA compound flame retardant and add it in dry form.