Unmanned Aerial Vehicle (UAV)-based pavement distress detection offers efficient and safe advantages. However, obstructions from road vehicles and the slender shape of cracks in UAV images challenge accuracy. To address this, this study established specific flight parameters, proposed the Historical Best Matching Image (HBMI) approach for data loss due to obstructions, and created the UAV-Crack500 dataset with 500 finely annotated crack images. Three algorithms with different loss functions were investigated, finding that the U-Net network combined with our Completely Asymmetric Loss (CAL) achieved the best performance, resolving the issue of class imbalance. Morphological analysis of the semantically segmented images provided precise crack morphology features. In complex scenarios, errors in features like crack area, length, mean width, and maximum width remained within 16%. This study establishes a comprehensive UAV-based pavement distress detection system, overcoming obstructions for accurate assessment.

To investigate the effect of styrene-butadiene-styrene (SBS) modifier content on the viscoelastic behavior of SBS-modified asphalt (SBSMA) at different temperatures and phase structures, the star SBS modifier was chosen to fabricate seven types of SBSMA with different contents. Multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and low-temperature frequency sweep tests were adopted to study the influence of SBS modifier content on the viscoelastic performance of SBSMA at high to low temperatures. The SBSMA’s microstructure with different contents was investigated using a fluorescence microscope. The results indicated that the change in non-recoverable creep compliance and creep recovery rate was bounded by 4.5% content at high temperatures, with an apparent turning point. The changing slope of content at less than 4.5% was much higher than that of the content greater than 4.5%. At medium temperatures, the fatigue life of SBSMA increased exponentially with the rising modifier content. The rate of increase in fatigue life was the largest as the content increased from 4.5% to 6.0%. At low temperatures, the low-temperature viscoelastic property index G (60 s) of SBSMA decreased logarithmically as the modifier content increased. In terms of the microscopic phase structure, the SBS modifier gradually changed from the dispersed to the continuous phase state with the increasing SBS modifier content.

Styrene-butadiene-styrene-modified asphalt binder (SBSMA), crumb rubber–modified asphalt binder (CRMA), and high-viscosity-modified asphalt binder (HVMA) have been widely used in porous asphalt concrete. However, the aging of the modified asphalt binder significantly affects the performance of the porous asphalt concrete. The main aim of this research is to quantitatively assess the aging degree of finished product–modified asphalt binders of SBSMA, CRMA, and HVMA at high, medium, and low temperatures, and to explore the aging mechanism at the microscopic level. This study used rolling thin-film oven and pressurized aging vessel to simulate the aging of asphalt binders. Dynamic shear rheometer, bending beam rheometer, Fourier transform infrared spectrometry, thin-layer chromatography with flame ionization detection, and scanning electron microscopy were employed to investigate how aging affects the rheological and microscopic properties of finished product–modified asphalt binder. The results showed that at high temperatures, short-term aging significantly impacted HVMA [change rate of the rutting factor $(\mathrm{CRRF})=18.9\%$ ], while long-term aging had an enormous influence on CRMA ($\mathrm{CRRF}=179.5\%$ ). Short-term aging had the greatest effect on the fatigue property at medium temperature of CRMA [change rate of $N_f$ $(\mathrm{CR}{N}_f)=59.9\%$ ], followed by SBSMA ($\mathrm{CR}{N}_f=46.1\%$ ) and HVMA ($\mathrm{CR}{N}_f=26.2\%$ ). However, the effect of long-term aging on the fatigue properties of HVMA ($\mathrm{CR}{N}_f=99.2\%$ ) is the largest, followed by that of CRMA ($\mathrm{CR}{N}_f=95.8\%$ ) and SBSMA ($\mathrm{CR}{N}_f=56.6\%$ ). At low temperature, compared with CRMA and HVMA, aging had the greatest influence on the low-temperature rheological properties of SBSMA. In addition, the three finished product–modified asphalt binders exhibited similar changes in microscopic level after aging.