Road performance and durability of high-modulus asphalt mixtures in cold and arid regions of Northwest China

In the cold and arid regions of Northwest China, long and steep-grade asphalt pavements are subjected to severe service conditions such as large temperature fluctuations, freeze–thaw cycling, heavy freight traffic, low-speed climbing and braking, and sustained shear stress. These actions collectively accelerate the development of rutting, cracking, moisture-induced damage, and premature deterioration in conventional asphalt mixtures. To enhance pavement durability and operational safety, this study investigated the pavement performance and long-term field behavior of BBME-13, a high-modulus asphalt mixture, through a case study of a national highway project in Northwest China. The study aimed to optimize the mixture design and elucidate its mechanical performance, moisture resistance, microstructural reinforcement mechanism, and durability evolution under complex in-service conditions.

HMB-W high-modulus asphalt was employed as the binder, and SBSAC-13 was used as the reference mixture. The optimum asphalt–aggregate ratio was determined by integrating Marshall volumetric parameters with mechanical performance requirements, including bulk density, air voids, voids in mineral aggregate, asphalt saturation, Marshall stability, flow value, dynamic modulus, moisture stability, and construction workability. Laboratory tests—freeze–thaw splitting, seasonal permeability, rutting, and dynamic modulus tests—were conducted to evaluate moisture susceptibility, impermeability, high-temperature deformation resistance, stiffness, and viscoelastic response. Scanning electron microscopy was employed to characterize the microstructural morphology and interpret the interfacial reinforcement mechanism. In addition, a 4-km-long, steep-grade test section was monitored for 24 months. The Pavement Condition Index, Riding Quality Index, Pavement Quality Index, Sideway Force Coefficient, and pavement deflection were measured quarterly to assess field durability.

The optimum asphalt–aggregate ratio of BBME-13 was determined to be 6.2%, corresponding to an asphalt content of 5.84%. Compared with SBSAC-13, BBME-13 exhibited markedly higher Marshall stability, reaching 28.38 kN, approximately 2.96 times that of the reference mixture, whereas its flow value decreased to 3.7 mm, indicating higher stiffness and stronger resistance to shear deformation. In the freeze–thaw splitting test, the initial tensile strength of BBME-13 reached 2.10 MPa, 53.3% higher than that of SBSAC-13. After freeze–thaw conditioning, its residual tensile strength remained at 1.90 MPa, with a tensile strength ratio of 90.6%, demonstrating strong resistance to moisture-induced and freeze–thaw damage. During seasonal permeability testing, the permeability coefficient remained below 55.25 mL/min and exhibited smaller fluctuations than those of SBSAC-13, indicating a denser and more stable internal pore structure. Under high-temperature and heavy-load conditions, the dynamic stability of BBME-13 was 1.6–2.6 times that of SBSAC-13. At 20 ℃ and 10 Hz, its dynamic modulus reached 16238 MPa, approximately 1.84 times that of SBSAC-13; even at 20 ℃ and 0.1 Hz, it remained at 7632 MPa, which is 2.37 times that of the reference mixture. Microscopic observations indicated that the rough and porous aggregate surface facilitated asphalt mortar penetration and mechanical interlocking, thereby enhancing interfacial bonding and inhibiting moisture-induced stripping and microcrack propagation. Field monitoring corroborated the laboratory findings. After 24 months of service, the Pavement Condition Index and Pavement Quality Index remained above 96, the Sideway Force Coefficient exceeded 54, the deflection values remained stable between 8.78 and 9.74 (expressed in units of 0.01 mm), and the cumulative deterioration rates of the key indicators were below 2.1%.

BBME-13 exhibited favorable rutting resistance, moisture stability, impermeability, stiffness, and long-term durability under complex service conditions, including cold–arid climate, heavy traffic loading, and long steep-grade pavements. These performance advantages suggest that BBME-13 can effectively accommodate the severe service environment of asphalt pavements in the cold and arid regions of Northwest China and has considerable potential for extending pavement service life and improving operational safety.