## 1 Introduction  
Asphalt, though comprising only about five percent of the road mixture, plays a crucial role in the performance of roads. However, pure asphalt often fails to meet the demanding performance criteria required to resist high-temperature flow and prevent low-temperature cracking. This inadequacy is largely due to increasing traffic volumes, heavier loads, and more severe weather conditions. To address these challenges, asphalt is fortified with various additives to enhance its resistance to temperature fluctuations and repetitive heavy traffic loads [1]. In recent years, the use of modified binders has gained significant traction. This trend is driven by the strong inclination of public agencies to invest in durable pavement solutions, the increasing demand for high-performance hot-mix asphalt (HMA) pavements, and the adoption of Superpaye asphalt binder standards in response to economic and environmental concerns [2, 3, 4, 5]. One promising additive for asphalt modification is Trinidad Lake asphalt (TLA). TLA is known for its reliable characteristics, dense composition, and exceptional rheological qualities. It consists mainly of soluble bitumen, mineral matter, and various minor constituents [6, 7]. TLA exhibits a high softening point, minimal penetration, excellent thermal stability, and exceptional chemical stability. Additionally, TLA offers excellent adhesive properties and remarkable stability, making it compatible with petroleum asphalt due to their similar chemical compositions. TLA-modified binders exhibit enhanced durability, reduced sensitivity to temperature fluctuations and permanent deformation, improved resistance to aging, high rigidity, lower solvent solubility, and minimal phase separation [8; 9; 10]. However, higher rigidity can reduce workability, pose compaction challenges, and lead to potential premature field failure, negatively impacting pavement performance [7]. Studies on the rheological properties of TLA-modified binders have shown that their varied chemical components and colloid matrix result in different levels of compatibility, leading to diverse performance outcomes [11; 12]. Increasing TLA replacement percentage can enhance pavement stiffness which only reduces life span of the pavement [10]. To address the stiffness issue, crumb rubber, derived from end-of-life tires (ELIs), is employed as a modifier. crumb rubber has been used since the early 1960s to improve pavement performance by reducing stiffness [13; 14; 15]. However, adding a significant amount of crumb rubber to an asphalt concrete mixture can increase its viscosity, complicating the laying and compaction processes, and impacting pavement resilience [16; 17]. To mitigate high viscosity, this study employed WMA-LEADCAP (WMA-LC) and untreated crumb rubber with a particle size of \(\leq\)0.5 mm. Extended blending times can significantly affect pavement performance, so the blending duration was limited to 30 min. Previous research has shown that LC, which utilizes special chemicals, effectively lowers the temperatures required for mixing and compacting asphalt mixes. The addition of LC also significantly reduces the stiffness and viscosity of the modified binder, as noted in previous studies [18; 19; 20; 21]. This reduction in stiffness and viscosity not only improves working conditions by lowering pollutants in asphalt fields but also offers numerous advantages. These benefits include reduced fuel consumption, extended paving durations, and increased hauling distances. Additionally, the technology allows for early traffic openings, minimizes binder aging, and decreases the likelihood of cracking [22]. The main objective of this study is to produce high-performance warm mix asphalt by incorporating crumb rubber modifier (CRM) and Trinidad Lake asphalt (TLA). The approach involves gradually increasing CRM concentration by 5% with each iteration, reaching a maximum of 10% to reduce viscosity.