Yang Datian

Water damage under the coupled effects of traffic load and pore water pressure (PWP) is a primary cause of early failure in asphalt pavements. Although dense-graded pavements generally have low void ratios, excess PWP poses a severe threat to durability under extreme conditions. These conditions include heavy rainfall, water accumulation in wheel tracks, and upward capillary water rise. In this study, a mesoscopic model considering fluid–solid coupling effects was established using the Particle Flow Code in the 2 Dimensions (PFC2D) platform, which is based on the discrete element method (DEM). A parallel-bonded stress corrosion model was introduced to describe damage evolution. The results show that the maximum positive PWP increased monotonically with load, reaching a distinct peak value at a critical loading frequency under specific load amplitudes. At this critical frequency, the fatigue life was significantly shortened compared to lower-frequency conditions. The PWP response exhibited a clear phase lag relative to the applied load, with the lag angle increasing alongside frequency. Furthermore, the absolute value of the minimum PWP continued to increase with fatigue damage accumulation. This indicates that regions with a vacuum suction effect were continuously expanding, which is a key reason for asphalt film stripping from the aggregate surface. These findings provide a theoretical basis for understanding mesoscopic water damage mechanisms in asphalt pavements and offer a reference for durability design.

To address the shortage of the aggregate used in a hot mix asphalt (HMA) pavement in Guangxi, properties such as the aggregate crushing, polished stone, and Los Angeles abrasion values of a type of hard sandstone aggregate used in HMA were tested after various conditioning treatments. The hard sandstone aggregate met the technical requirements for aggregate in HMA. In addition, the influence of the Marshall compaction on the hard sandstone aggregate-combined grading was tested. The combined grading curve changed a little, and the aggregate satisfied the corresponding technical requirements. Therefore, according to the abovementioned results, the hard sandstone aggregate can be used as a coarse aggregate in HMA.

In order to study the variations of the non-Darcy flow permeability coefficient and the porosity of permeable friction courses (PFCs), as well as the effects of the coupled seepage and stress fields on them, repeated uniaxial compression tests were carried out under the coupled action of water and a load. A set of water and load coupling tests were conducted, and a non-Darcy flow permeability coefficient tester was also made. After the PFC-13 specimen was carried out by the repeated uniaxial compression test under the water and load coupling, the total air void ratio and effective air void ratio were measured by the vacuum sealing method, and the non-Darcy flow permeability coefficients were obtained by a non-Darcy flow permeability coefficient tester. It was found that the coupled action of water and a load caused the total air void ratio, effective air void ratio, and permeability coefficient to sharply increase and reduced the number of repeated uniaxial compression cycles. These results are helpful for the design, construction, and maintenance of PFC mixtures.

To evaluate the moisture stability of a hard sandstone asphalt mixture, a testing section of a hard sandstone asphalt mixture was prepared in the laboratory. The accelerated pavement testing (APT) with the one-third-scale model mobile load simulator (MMLS3) was conducted in this testing section under temperature and water-coupled conditions. As the APT number increased, the elastic modulus of the hard sandstone asphalt mixture pavement gradually decreased. The average elastic modulus was 22.99 GPa after 160000 APT cycles. The bulk specific density of the sample rolled by the MMLS3 increased, and the residual indirect tensile strength ratio was 88.7%. Therefore, the hard sandstone asphalt mixture had good resistance to moisture damage, and hard sandstone aggregates can be used in a hot mix of asphalt.