###### Abstract  
This research investigates the synergistic impact of Trinidad Lake Asphalt (TLA) and Crumb Rubber Modifier (CRM) on the performance characteristics of PG 64-22 asphalt binder. Employing Superpave test analysis and Multiple Stress Creep Recovery (MSCR) testing, our study reveals that the incorporation of TLA significantly elevates the viscosity of the binder due to its high asphaltene content. This viscosity enhancement translates to increased stiffness and durability of the asphalt binder. Furthermore, CRM contributes to improved elasticity and deformation resistance, counterbalancing the stiffness induced by TLA. Our results indicate that the combined use of TLA and CRM not only boosts viscosity but also mitigates stiffness, thereby enhancing the binder's resistance to rutting, especially post-aging. However, an elevated concentration of TLA increases the risk of fatigue cracking, a concern effectively alleviated through the integration of CRM. At a critical temperature of \(-12\,^{\circ}\)C, Bending Beam Rheometer (BBR) tests demonstrate that TLA augments stiffness while CRM enhances low-temperature flexibility. This study underscores the necessity of optimizing TLA and CRM ratios to achieve a balance between enhanced performance and practical feasibility. The findings highlight the potential of TLA and CRM to substantially improve asphalt binder performance, contributing to the longevity and resilience of pavement structures. TLA; CRM; Superpave test; MSCR +
Footnote †: journal: Applied Sciences  
of 52-62% soluble bitumen, 33-38% mineral matter, 4% water of hydration, and other organic materials. It has been shown to increase stiffness in mixes due to its high inorganic content. However, the use of TLA alone in asphalt concrete is challenging, so it is generally blended with conventional petroleum-based asphalt binder [6]. TLA-modified binders exhibit increased stiffness and adhesion, reduced thermal susceptibility and permanent deformation, improved aging characteristics, and lower solubility in solvents. However, the increased stiffness may negatively impact pavement performance by reducing mixture workability, worsening compaction, and potentially leading to premature field failure [7]. To address the stiffness issue, crumb rubber from end-of-life tires (ELTs) can be used as a modifier. crumb rubber has been popular since the early 1960s for its ability to reduce stiffness and enhance pavement performance [8; 9; 10]. However, a high replacement content of crumb rubber can lead to increased viscosity, raising costs and making asphalt concrete difficult to lay and compact, thereby affecting pavement life [11; 12; 13]. To mitigate high viscosity, this study uses untreated crumb rubber with a reduced particle size of less than or equal to 0.5 mm, and the blending time is set to 30 minutes as recommended by previous studies, as increased blending time can negatively impact pavement performance [14; 15; 16]. Previous research has investigated the use of crumb rubber and Trinidad Lake Asphal (TLA) in modified binders, typically using a maximum replacement of 10% crumb rubber [17]. However, these studies lack an in-depth analysis of how the modified binder performs under various stress levels and at low temperatures. Building on this, our research reduces the replacement percentage of TLA to 20%, based on previous findings [18], with intervals of 10%. This adjustment is made because increased TLA content tends to increase the stiffness of the binder. Additionally, the maximum addition of crumb rubber to TLA-modified asphalt is capped at 10%, with intervals of 5%, to avoid excessively high viscosity values. For this study, we employ the wet process, specifically McDonald Technology, which has been identified as the most successful method for achieving homogeneous blending [19]. To evaluate the performance of the produced binder, we use the Superpave test method along with the Multiple Stress Creep Recovery (MSCR) test.