Asphalt pavement is widely used for expressways due to its advantages of flexibility, low cost, and easy maintenance. However, pavement failures, including cracking, raveling, and potholes, will appear after long-term service. This research evaluated the residual fatigue properties of asphalt pavement after long-term field service. Fatigue behavior of specimens with different pavement failure types, traffic load, service time, and layers were collected and characterized. Results indicate that after long-term field service, surface layer has a longer fatigue life under small stress levels, but shorter fatigue life under large stress levels. Longer service time results in greater sensitivity to loading stress, while heavier traffic results in shorter fatigue life. Surface and underneath layers present very close fatigue trend lines in some areas, indicating that the fatigue behavior of asphalt mixture in surface and underneath layers are aged to the same extent after eight to ten years of field service.

: Microbial-induced carbonate precipitation (MICP) has emerged as a promising eco-friendly and cost-effective alternative for improving the strength and stability of low-cohesion soils. This review provides an in-depth analysis of the microscopic mechanisms, implementation methods, and macroscopic properties of MICP in soil enhancement. The biogeochemical processes underlying MICP, including urea hydrolysis, denitrification, sulfate reduction, photosynthesis, and iron reduction, are discussed in detail. Various MICP implementation methods, such as two-phase treatment, one-phase treatment, and ex-situ mixing, are reviewed, highlighting their respective advantages and limitations in reinforcing low-cohesion soils. The review also addresses the performance of MICP-treated soils, including improvements in strength, stiffness, permeability, and durability. Furthermore, the key challenges and future prospects for microbial soil reinforcement technologies are summarized. Future research should focus on optimizing nutrient supply, enhancing bacterial retention and activity, controlling the crystallization process, conducting pilot projects, and reducing treatment costs. These efforts are crucial for advancing the practical application of MICP in sustainable infrastructure construction. This review aims to advance the understanding of MICP and its potential for sustainable soil improvement, offering valuable insights for geotechnical engineers.

Well-graded asphalt mix with the merits of high sound absorption, low water permeability, excellent strength, and easy construction is an important option for high-speed railway substructures. On the basis of finite element method, a model with conventional ballasted trackbed (T₀) and four ballasted trackbeds models with different positions of asphalt layer were analyzed, in which 15 cm thick asphalt layer was used to replace the different sub-track layers, the bottom and the top of upper subgrade and of ballasted trackbed, named as T₁, T₂, T₃, and T₄, respectively. The results showed that the range of peak vertical accelerations on the top of subgrade surface of T₂ and T₄ were smaller than T₁ and T₃; T₁ and T₂ perform better in decreasing the maximum vertical deformation of subgrade than T₃ and T₄; the maximum transversal tensile strain of T₄ is almost twice than the other three. The trackbed bears more stress when the asphalt layer is located at the lower part of railway trackbed.