# Evaluation of Low-Temperature Performance of Recycled
## 1 Introduction  
In recent years, the widespread use of reclaimed asphalt pavement (RAP) in road engineering construction has become increasingly popular due to the depletion of non-renewable raw materials and rising petroleum costs [1]. Many countries and regions have adopted RAP to produce a hot-mix recycled asphalt mixture and a warm-mix recycled asphalt mixture, and the blending ratio steadily increases [2]. The Research indicates that incorporating 50% RAP into the mixture can lead to a cost reduction of approximately 24-35% in asphalt mixture production, a figure that may be further increased by the rapidescalation of asphalt prices [3]. Utilizing RAP not only effectively lowers construction expenses and reduces natural resource consumption but also addresses waste material disposal concerns, ultimately yielding significant economic and environmental benefits [4]. However, the RAP content in recycled asphalt mixtures (RAMs) is still low due to various factors, such as the mixing process, rejuvenating agent, manufacturing process grading type, production temperature, mixing time, application environment, expected performance, RAP source, and properties. Consequently, the full benefits of RAP may not be fully realized [5]. Most of Northern China is in a seasonally frozen area, with cold temperatures in winter. Low-temperature cracking has become one of the most common conditions of asphalt pavement. When the thermal stress generated by the thermal shrinkage of the asphalt mixture at low temperatures exceeds its tensile strength, low-temperature cracking will occur. The quality of the mixture mainly depends on the quality of its constituent materials. As one of the main components of RAM, RAP includes asphalt concrete milled from the existing infrastructure and asphalt mixture discarded during the production process. These asphalt mixtures, which are exposed to complex environments for a long time during the production, mixing, rolling, and service processes, will age. As a result, the physical and chemical properties of asphalt mixtures change after aging. The variations in the production processes of asphalt mixtures; the geographical and natural environments of milled pavement locations; and differences in RAP production, storage, transportation cycles, and exposure environments all contribute to variations in RAP's thermal history and subsequent aging differences [6]. Adding RAPs with different thermal histories to an asphalt mixture will have varying impacts on the road performance of the mixture, especially the low-temperature crack resistance [7; 8]. Therefore, studying the impact of different thermal history RAPs on the LTP of RAMs is necessary and can provide a reference basis for the use of RAPs from different sources in the northern region. In order to evaluate the low-temperature performance of RAMs, a lot of research is used. [PERSON] et al. conducted flexural creep tests using a bending beam rheometer and found that the addition of RAP reduced the creep stiffness of RAMs at low temperatures [9]. [PERSON] used the fracture energy method to conduct a semicircular cross-section fracture test study on asphalt mixtures with different RAPs and recycled asphalt shingle (RAS) content. The results indicated a consistent drop in the fracture energy as the RAP and RAS increased [10]. [PERSON] examined the low-temperature cracking resistance of different RAMs with varying RAP content through 3 PBB and TSRST tests, revealing that as the RAP content increased, the fracture temperature and transition temperature rose while the failure strain and fracture energy decreased, indicating a decrease in low-temperature performance [11]. [PERSON] et al. observed that, as the short-term aged RAP and the long-term aged RAP content increased, the fracture energy decreased, and the low-temperature crack resistance weakened under different traffic load levels [12]. [PERSON] et al. utilized the semicircle bending test (SCB) to assess the impact of RAP on the crack resistance of asphalt mixtures.