Preparation And Properties Of Polyphosphoric Acid/Crumb Rubber Modified Bitumen

With the development of automobile industry, more and more discarded tires threat the environment seriously. At the same time, with the rapid development of highway construction, there is a growing demand for high performance of modified asphalt. The waste tires are processed into powder and produce modified asphalt which can solve both the environmental problems and promote road construction and reduce the cost. But some problems like low ductility, high viscosity and poor high temperature storage stability limit the application of crumb rubber asphalt. In this paper, the process temperature has been increased to promote the degradation of crumb rubber and increase the ductility. Phosphoric acid(PPA) has been used as stabilizer to improve the high temperature storage stability and third vacuum side stream distillate has been used to reduce the viscosity of crumb rubber asphalt to make the performance of crumb rubber asphalt better. Some main conclusions are as follows:(1)The preparation methods of crumb rubber asphalt has a great impact on its physical properties, the study has found that the choice of content is 20 percent of 40 mesh crumb rubber, and under the temperature of 200 ℃ to react one hour can obtain the optimal physical properties, including significantly increase on its ductility.(2) PPA can improve the viscosity and softening point and reduce the penetration of crumb rubber modified asphalt; third vacuum side stream distillate can improve the flow properties of crumb rubber modified asphalt and improve its penetration. Following the optimum content(PPA0.2% third vacuum side stream distillate 2%), PPA and third vacuum side stream distillate have been added to the crumb rubber asphalt, through synergy effect, physical properties of crumb rubber modified asphalt can be improved.(3) Both PPA and third vacuum side stream distillate can improve the high temperature storage stability. PPA promotes the change of bitumen component from sol structural to gel structure, which make bitumen easier to form a uniform pitch phase system. Third vacuum side stream distillate can promote the combination of crumb rubber and asphalt to improve high temperature storage stability. Synergy effect of PPA and third vacuum side stream distillate makes the high temperature storage stability of crumb rubber asphalt optimal.(4) The TFOT ageing test results show that viscosity increasing rate, penetration increasing rate, ductility increasing rate, softening point increasing rate and ageing index have been reduced significantly, which indicates that the anti-aging properties of PPA and crumb rubber modified asphalt behaves better than normal crumb rubber asphalt.(5) The application of PPA and third vacuum side stream distillate in crumb rubber asphalt showed better behavior on fatigue resistance. It is because of the application of PPA and third vacuum side stream distillate accelerates the combination of rubber particles and base asphalt which reduces the number of suspended rubber particles and contributes to the uniformly display of the system. As a result, reduces energy losing from the repeated loads. Another contributing factor is the lubrication effect of third vacuum side stream distillate.