The double-layer one-time-paving technology for asphalt mixtures enhances the interlayer adhesion and stability of pavement by simultaneously laying and compacting two layers of asphalt mixture, demonstrating improvements over traditional layer-by-layer paving and compaction methods. Based on this technology, the effects of paving techniques, mixture types, and structural layer thickness on the low-temperature crack resistance of pavement at −10 °C were investigated. Results indicated that, compared to traditional paving methods, the maximum tensile strain and bending strain energy density of pavement using the double-layer one-time-paving technique increased by at least 14% and 20%, respectively, under a 95% confidence level. Compared to the AC-13 + AC-25 mixture combination, the AC-16 + AC-20, AC-16 + AC-25, and AC-13 + AC-20 combinations showed increases in maximum tensile strain by at least 25%, 15%, and 15%, and in bending strain energy density by at least 57%, 38%, and 31%, respectively. Compared to the 5 cm + 5 cm thickness combination, the 4 cm + 6 cm and 3 cm + 7 cm combinations exhibited increases in maximum tensile strain by at least 14% and 22%, and in bending strain energy density by at least 16% and 29%, respectively. To effectively improve the low-temperature crack resistance of asphalt pavement at −10 °C, it is recommended to adopt a double-layer one-time-paving structure with a 3 cm AC-16 upper layer and a 7 cm AC-20 lower layer, providing insights for more durable asphalt pavements in cold climates.

To investigate the performance degradation of emulsified asphalt cold recycled mixtures (CRM) during service, this study selected a 10 km section of the cold recycled layer (CRL) from the Changjiu Expressway reconstruction project as the research subject. The deterioration patterns of key pavement performance indicators—including the Pavement Condition Index (PCI), Riding Quality Index (RQI), Rutting Depth Index (RDI), and Pavement Structure Strength Index (PSSI)—were analyzed in relation to cumulative equivalent axle loads over a 7-year service period. Concurrently, comparative evaluations were conducted on the mechanical properties, water stability, high-temperature performance, low-temperature crack resistance, and fatigue characteristics between in-service and laboratory-prepared emulsified asphalt CRM. The results demonstrate that after seven years of service, the emulsified asphalt cold recycled pavement maintained excellent performance levels, with PCI, RQI, RDI, and PSSI values of 92.6 (excellent), 90.1 (excellent), 88.5 (good), and 93.4 (excellent), respectively. Notably, while the indirect tensile strength and unconfined compressive strength of the CRL increased with prolonged service duration, other performance metrics—including the tensile strength ratio, shear strength, fracture work, and fracture energy—exhibited an initial improvement followed by gradual deterioration. Additionally, increased traffic loading during service led to a reduction in the residual fatigue life of the CRM. Interestingly, the study observed a temporary improvement in the fatigue performance of CRM during the service period. This phenomenon can be attributed to three key mechanisms: (1) continued cement hydration, (2) secondary hot compaction effects, and (3) diffusion and rejuvenation between fresh and aged asphalt binders. These processes collectively contributed to the partial recovery of aged asphalt strength, thereby improving both the mechanical properties and overall road performance of the CRM. The findings confirm that cold recycled pavements exhibit remarkable durability and maintain a high service level over extended periods.

After the comprehensive transformation of combustion system for a 1000MW ultra-supercritical boiler, there are a series of problems such as combustion deviation of left and right sides, high CO content at the outlet of economizer, high carbon content of slag and poor low-nitrogen combustion effect due to unsatisfactory operation adjustment. In order to solve the problem of abnormal combustion, combustion optimization adjustment test was carried out, including oxygen leveling, secondary throttle adjustment, exhaust throttle adjustment, optimal oxygen adjustment. By combustion optimization adjustment test, the economy, safety and environmental protection of the boiler combustion get obvious increase. Oxygen distribution is more uniform along the furnace width direction, and the problems of abnormal combustion are solved significantly. The wall temperature distribution is more uniform along the furnace width, and the wall temperature deviation is decreased obviously. The boiler efficiency under 1000MW condition increased by 0.41 percentage points compared with that before adjustment, reaching the design boiler efficiency under THA condition.