## 1 Introduction  
With the rapid development of China's automobile manufacturing industry, the popularity of automobiles in China is increasing, leading to an increasing number of waste tires, and a large number of abandoned waste tires that can cause environmental pollution, as well as great fire safety hazards in the random piles of waste tires [1, 2, 3]. Bituminous pavement has the advantage of good driving comfort and is widely used in China's high-grade highways, but it is also prone to rutting and cracking, which affects the safety and comfort of driving. The crumb rubber (CR) obtained from the crushing of waste tires is added to the neat bitumen and then made into rubber modified bitumen (RMB) by mixing and shearing at high temperatures [4, 5], which not only solves a large number of waste tires but also reduces the amount of neat bitumen and saves construction costs [6]. Some studies have shown that the use of RMB to pave pave pavements can improve high and low temperature performance and fatigue resistance, and has excellent resistance to deformation and noise reduction [7, 8, 9, 10]. However, the interaction mechanism between CR particles and bitumen is mainly physical swelling, and it is difficult to disperse CR particles in bitumen and form a cross-linked mesh structure, which can easily lead to RMB segregation problems during storage, thus limiting its application. Many studies have used composite modification techniques to improve the overall performance of RMB by incorporating other types of modifiers into RMB [11; 12; 13; 14]. [PERSON] et al. found that the temperature sensitivity of the bitumen was improved and its bituminous pavement noise reduction performance was excellent after the composite modification of CR and styrene-butadiene-styrene (SBS) [15]. [PERSON] et al. studied the aging performance of CR and SBS composite modified bitumen and found that after aging the aromatic hydrocarbon content in the bitumen was reduced and the asphaltene content increased, and the improvement of the performance of the bitumen by the composite modification of SBS and CR was mainly reflected in the high temperature performance [16]. [PERSON] et al. prepared SBS/CR composite modified bitumen by high-speed shear and studied its rheological properties and storage stability, pointing out that the addition of CR and SBS to the bitumen can significantly increase its storage modulus, loss modulus, and viscoelasticity, thus enhancing the ability of asphalt pavements to resist permanent deformation [17]. [PERSON] et al. added CR and SBS to the neat bitumen and studied its rheological properties and microstructure and found a significant improvement in the viscoelasticity of the composite modified bitumen. The morphology of the composite modified bitumen changed significantly during the preparation process, and its phase morphology changed from one bitumen phase with a dispersive polymer phase to two continuous phases that are cross-linked with each other, while the bitumen would react chemically with SBS and CR [18]. The chemical reaction between sulfur and bitumen results in chemical bonds and chemicals that cause the bitumen molecular chain to become a three-dimensional mesh structure from a planar mesh structure and an increase in viscosity [19; 20], resulting in an improvement in the mechanical properties and high temperature stability of its bitumen mixture [21; 22]. The interaction between sulfur and bitumen increases over time [23], which is associated with the recrystallization of sulfur in bitumen [24], and the cross-linking of sulfur with the components in CR to form a network structure that enhances the performance of RMB [25]. RMB is subject to higher temperatures than the neat bitumen during pavement construction, which makes it more susceptible to the effects of aging, and will also experience the effects of aging during the life of the pavement, so aging occurs throughout the life cycle of RMB.