Study On The Performance Of SBS/Crumb Rubber Composite Modified Asphalt

Using scrap tire crumb rubber (CR) to modify asphalt (CRMA) can not only improve the high temperature performance and anti-aging properties of base asphalt, but also reuse waste tyres. However, CRMA has a limited performance in low temperature performance and poor stability. Styrene-butadiene-styrene block copolymer (SBS) modified asphalt (SBSMA) has advantages of excellent high and low temperature performance, good viscoelastic properties, as well as great rutting resistance, fatigue resistance, but SBS is expensive, causing high cost in paving road. The SBS/CRMA was composited with CR and SBS, in which the amount of SBS was decreased from 4%～6% to 2%.Fistly, the influencing factors of SBS/CRMA were explored to get the significant factors. And the optimal preparation conditions were got through orthogonal experiment. Then general properties, rheological properties, aging properties of SBS/CRMA were explored. The general properties rheological properties of SBS/CRMA short tern aging were analyzed, and the degree of SBS/CRMA short tern aging was analyzed by infrared. In order to reduce the viscosity of SBS/CRMA, and polyphosphoric acid (PPA) and sulfur powder were added to modify asphalt. Finally, fluorescence microscopic structurethe, the IR, TG-DSC and DSR were used to study the model of mixing mechanism.The results showed that the SBS/CRMA had ductility at 5℃ of 32.7 cm, softening point of 78.0℃, viscosity at 135℃ of 42 Pa·s, and segregation of softening point of 0.6℃ under the optimal preparation conditions of the CR1 mesh of 40-60, crumb rubber amount of 25%, LG501 of SBS type, SBS amount of 2%, furfural extract oil of 8%, stirring temperature of 210℃ and stirring time of 2.5 h. SBS/CRMA was more flexible at low temperature and harder at high temperature, and it had better temperature susceptibility, better rutting resistance and anti-aging performance. The modified asphalt has ductility at 5℃ of 27.6 cm, softening point of 75.0℃, viscosity at 135℃ of 4.6 Pa’s, and segregation of softening point of-2.3℃ under the preparation conditions of SBS amount of 3%, crumb rubber amount of 10%, PPA of 1% and sulfur powder of 0.2%. And compared with SBS/CRMA, the viscosity of additive modified asphalt was significantly reduced. The SBS/CRMA was mainly mixed physically, and a more stable three-dimensional network structure was formed in asphalt. The mixing mechanism model was that a network structure of SBS was formed in asphalt, then rubber hydrocarbon molecules chain degradating from CR got into the network structure of SBS, and the rubber hydrocarbon molecules chain and SBS crosslinked to more stable three-dimensional network structure.