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Phosphogypsum (PG) is an industrial solid waste generated during the preparation of phosphoric acid, which is produced in large quantities and stockpiled or discharged into the sea. This study aims to design sustainable pavement base materials constituting significant PG content. The physical and chemical properties of the raw materials were first tested. The optimum moisture content and maximum dry density of specimens were determined by compaction tests. The unconfined compressive strength (UCS), split tensile strength (STS), freeze-thaw cycles, and shrinkage tests were used to evaluate the mechanical performance of phosphogypsum pavement base material (PPBM). Furthermore, the interaction mechanism was investigated by applying scanning electron microscope (SEM) and Fourier-transformed infrared (FTIR) tests. The results showed that the 7-day UCS of PPBM with cement content 8%–12% was greater than 3 MPa. The specimens retained 91.3% unconfined compressive strength over five freeze-thaw cycles. Unlike traditional semirigid base materials, the PPBM exhibited no shrinkage strain, which is manifested by the growth of expansion strain with increasing amounts of PG. Through microscopic observation, the PPBM produced ettringite (AFt) and calcium-silicate-hydrate (CSH) with the extension of curing time, which is consistent with the analysis of FTIR spectrums. The crystallized water in the PG participates in the hydration reaction. [ABSTRACT FROM AUTHOR]

Skid-resistance performance of a runway greatly influences aircraft landing safety. A wet runway significantly increases the incidence rates of aircraft overrun. To study the influence of the skid-resistance performance of a runway on aircraft landing, a co-simulation method is proposed. First, a finite element (FE) model of the local tire-water film-runway simulation is established to obtain the combination coefficient-slip ratio curve of a tire on a wet runway. Second, a global model of an Airbus A320 virtual prototype (VP) is created. Then, on the basis of fuzzy control theory, a two-dimensional (2D) fuzzy controller of the aircraft AB is established. The friction coefficient-slip ratio curve of the tire on the wet runway obtained in the local simulation is introduced into the full-scale hydroplaning simulation model of the aircraft. Finally, the global-local multiscale simulation method is used to analyze the skid-resistance behaviour of the aircraft on three types of runways. It is found that the increase of water film thickness of the pavement and the increase of the grounding speed cause the attenuation of the friction coefficient of a runway, finally causing the reduction of the deceleration rate of the aircraft and the increase of the braking distance. [ABSTRACT FROM AUTHOR]

Accurate monitoring of concrete pavement support condition is critical for pavement maintenance. This paper proposed a novel support condition monitoring method using distributed optical fiber sensing (DOFS) technology. The DOFS-based method can precisely monitor the support condition on a larger scale. Single-mode optical fiber with a particular rubber encapsulation was applied as a compression sensor, measuring the interfacial compression status between the concrete pavement slab and the pavement base through a compression-to-strain transfer mechanism. Finite element analysis (FEA) and laboratory experiments were conducted to compression-to-strain transfer mechanism. It was revealed that the average compression-to-strain transfer efficiency reached over 1900 μϵ/mm. The design parameters of the compression sensor were also provided based on the FEA and experiment results. A quasi-distributed sensing system was developed to capture the two-dimensional support condition by connecting the sensors in a particular path. The sensing system's effectiveness was demonstrated by conducting full-scale tests and using the pressure-sensitive film (PSF) as a comparison. The test results showed a great deal of applicability for support condition monitoring under concrete pavement. [ABSTRACT FROM AUTHOR]

Studying the hydroplaning behaviour is crucial for enhancing the safety of aviation during the landing stage. Due to the special nature of the aviation field, such as high aircraft velocity, wheel load and operating frequency, accurate numerical simulation is considered an effective method for investigating the tire hydroplaning behaviour. In this study, a fluid–solid coupling model was established using the coupled Eulerian–Lagrangian algorithm to analyze the hydroplaning behaviour. To reveal the influences of factors such as the runway texture, slip ratio, velocity and water-film thickness on tire hydroplaning, some parameters such as the skid number, water distribution, and tire inflation pressure were extracted. Moreover, the real pavement textures of stone mastic asphalt, an open-graded friction course, and asphalt concrete were determined to construct a real runway model and water-film thicknesses of 3, 7, and 10 mm were selected to study their effects on aircraft hydroplaning. The numerical simulation results were verified by calculating the braking distance and conducting trailer test, and the results prove that the numerical model can be applied for the multifactor analysis of tire hydroplaning behaviour. [ABSTRACT FROM AUTHOR]