# High-Temperature Rheological Properties of Asphalt Mortar Modified with Spent FCC Catalysts
## 1 Introduction  
Solid wastes, including industrial slags and construction waste, are valuable renewable resources [1]. After proper treatment, these materials can be effectively utilized in various applications such as bridges, dams, and airport roads [2; 3; 4]. Given the significant consumption of construction raw materials in road projects, and in line with global efforts to conserve energy, reduce emissions, and foster sustainable infrastructure, the field of road construction has emerged as a pivotal domain for the resourceful reuse of the aforementioned solid wastes. Considerable research has been conducted both domestically and internationally on the application of solid waste in road construction. [PERSON] et al. [2] incorporated steel slag as a mineral filler in asphalt mixes, resulting in improved deformation resistance and reduced low-temperature cracking of the asphalt binder. [PERSON] et al. [5] pre-treated electric furnace slag to replace a portion of the coarse aggregates and observed enhanced durability inasphalt mixes. Extensive research has also been conducted on waste tire mastic powder-modified asphalt, focusing on modification mechanisms, production processes, and road performance [6; 7]. As one kind of hazardous solid waste, the spent FCC catalysts (S-FCC-Cs) are generated in large quantities every year and are challenging to handle [8]. Some studies on the application of S-FCC-Cs exist in the field of catalysis, adsorption, construction, and others [9; 10; 11; 12; 13]. However, the application of S-FCC-Cs on an industrial scale is still limited. For instance, large-scale applications in urban fields or road engineering and so on [14; 15; 16]. FCC catalysts are complex mixtures that serve as catalytic reaction media formed through various physical and chemical reactions. They primarily consist of active substances, matrices, and binders [1; 17; 18], and are widely employed in the processing of petroleum light oil, during which certain raw materials are converted into coke. This coke leads to catalyst metal poisoning or pore blockage, resulting in the temporary deactivation of the active sites [18]. Consequently, a significant amount of spent catalysts with depleted activity precipitates. FCC spent catalysts contain heavy metal elements, such as Ni and V, which can be employed in the production of ceramics, bricks, and zeolites after appropriate treatment [19; 20; 21; 22; 23]. [PERSON] et al. [24; 25] demonstrated that bituminous materials effectively immobilize heavy metals and radioactive elements. Moreover, the porous Y-type molecular sieve structure of FCC spent catalysts possesses a certain adsorption capacity. Hence, some studies [26; 27; 28] have proposed the substitution of spent FCC catalysts as fillers in asphalt mixtures, instead of mineral powder. Consequently, the utilization of spent FCC catalysts in asphalt mixtures can partially enhance the road performance of asphalt mixes. A previous study proved that the mechanical and durable properties of asphalt mixtures are related to asphalt mortar. It is essential to study the variations of the properties of asphalt mixtures based on asphalt mortar's viscoelastic rheological properties [29]. For instance, [PERSON] et al. [30]. proved that the workability of asphalt mixtures is closely related to the viscoelastic properties of asphalt mortar based on dynamic shear rheological tests and digital image processing techniques. In addition, the high-temperature rheology of the asphalt binder pertains to the continuous strain and flow changes experienced by the binder over time after the application of a load. This property is closely associated with the high-temperature performance of an asphalt binder and can impact pavement issues such as rutting, waves, and undulations. Spent FCC catalysts exhibit a large specific surface area [31]. Consequently, when employed as fillers, they tend to adsorb more asphalt, thereby enhancing the high-temperature performance of the binder.