Study On Asphalt Modified With Scrap Passenger Car Tire Rubber

Rubber asphalt technology developed rapidly in recent years, the high requirements of road performance need more high-quality crumb rubber. Curmb rubber used now in asphalt rubber mainly is truck tire rubber. Passenger car tire is consumed by unlawful oil refining, which has great threat to environment and oil market. In order to achieve the reasonable and effective application of waste passenger tire rubber resource, this paper conducted studies on waste rubber-asphalt interaction, vulcanized rubber -asphalt interaction, regeneration process of passenger car tire rubber and reclaiming crumb rubber modified asphalt.Tire rubber was immersed in asphalt for different time at different temperatures to study the interactions between rubber and asphalt. The mass and cross-linking network change were investigated using extraction experiments and equilibrium swelling method, as well as thermal analysis. This study shows that the mass increase （MI） of rubber is approximately linear with 2t^1/2/d （t as swelling time, d as rubber thickness）; and the diffusion coefficient D of asphalt is related to the swelling temperature and rubber type. The cross-linking network structure of truck tire rubber can be destroyed when the swelling temperature reaches 190 oC, and the rubber disintegrats after 24 h. However,the cross-linking network structure of passenger car rubber changes less during the whole interaction period. Thermal analysis results shows that the glass transition temperatures of tire rubbers increase after swelling, due to the absorption of the asphalt. The initial decomposition temperature of tire rubbers increase after swelling, with the disappearance of decomposition peak of oil in rubber. Thermal analysis indicates that the exchange of rubber and asphalt components appeare during interaction.Vulcanized rubber with tire rubber formulation were prepared, equilibrium swelling ratio,mass loss rate and thermal analysis were used to find the differences of interaction with asphalt between NR and SBR. The results showed that asphlt had great effect to NR networks but few effect to SBR networks. The glass transition temperature of both NR and SBR increased when immersed in asphalt, crystalline components of asphalt diffused into rubber networks. The swelling law of NR is similar to that of truck tire rubber and the swelling law of SBR is similar to that of passenger car tire rubber. Tire aging had no fundamentally impact on the rubber-asphalt interaction. The peak of thermal decomposition rate of NR shifted to high temperature region,while that of SBR strenghened. Thermal oxidative degragation of vulcanized rubber also affect by rubber-apshlt interaction. The tensile strength,elongation at break, hardness of all swelled rubber decreased, swelled NR reduced the fastest and SBR the slowest. Storage modulus E’of swelled vulcanized rubber decreased with swelling time, the damping peak of NR disappear gradually, but that of SBR strenghened and shifted to high temperature region.Process of crumb rubber modified asphalt was explored. SEM and TGA curves showed that the main component of truck tire rubber is NR, while that of passenger car tire rubber is synthetic rubber. What is more, crumb rubber, been ground from passenger tire rubber, consisted of fibers with irregular sizes. Shearing test indicated that the particle size was inversely proportional to shear time. Filtration experiment found that the number of micron-sized particles of truck tire rubber increased significantly after 4 hours shearing,but that of passenger car tire rubber increased slowly. the phenomena that carbon black and inorganic fillers separated out happened. The penetration, ductility of modified asphalt increased by shearing process,while the soft point of modified asphalt decreased. When reclaimed ground tire rubber was used, the penetration, ductility of modified asphalt increased largely, and the viscosity of modified asphalt reduced.Reclaimed ground tire rubber （RGTR） was prepared by twin-screw extruder, and RGTR was used as modifier of asphalt. sol.-gel fractions indicated that hot shearing and activator can largely enhance the devulcanization and degradation; Penetration of RGTR modified asphalt increased substantially, while the value of softening point degree, elastic restitution, viscosity decreased accordingly; With the increase of RGTR content ,the penetration, ductility, elastic restitution of compound modified asphalt reduced and softening point degree, ductility of RTFOT increased. Microstructure of RGTR modified asphalt showed that particle size decrease outstandingly and the dispersion of rubber particles was improved.