The reuse in high-value materials is one of the important resource utilization approaches of phosphorus tailings. At present, a mature technical system has been formed on the reuse of phosphorus slag in building materials, and silicon fertilizers in the extraction of yellow phosphorus. But there is a lack of research on the high-value reuse of phosphorus tailings. In order to make safe and effective utilization of phosphorus tailing resources, this research concentrated on how to solve easy agglomeration and difficult dispersion of phosphorus tailing micro-powder, when it was recycled in road asphalt. In the experimental procedure, phosphorus tailing micro-powder is treated in two methods. One method is to directly add it with different contents in asphalt to form a mortar. Dynamic shear tests were used to explore the effect of phosphorus tailing micro-powder on the high-temperature rheological properties of asphalt influence mechanism of material service behavior. The other method is to replace the mineral powder in asphalt mixture. The effect of phosphate tailing micro-powder on the water damage resistance in open-graded friction course (OGFC) asphalt mixtures was illustrated, based on the Marshall stability test and the freeze–thaw split test. The research results show that the performance indicators of the modified phosphorus tailing micro-powder meet the requirements for mineral powder in road engineering. Compared with standard OGFC asphalt mixtures, the residual stability of immersion and freeze–thaw splitting strength were improved when replace the mineral powder. The residual stability of immersion increased from 84.70% to 88.31%, and freeze–thaw splitting strength increased from 79.07% to 82.61%. The results indicate that phosphate tailing micro-powder has a certain positive effect on the water damage resistance. These performance improvements can be attributed to the larger specific surface area for phosphate tailing micro-powder than ordinary mineral powder, which can effectively adsorb asphalt and form structural asphalt. The research results are expected to support the large-scale reuse of phosphorus tailing powder in road engineering.

Due to the complex organic properties of asphalt materials, the heating process during asphalt pavement construction will lead to the release of asphalt VOCs‧ Asphalt VOCs volatilization will cause irreversible harm to both the environment and health of construction workers‧ Researchers in the field of road construction have carried out extensive research on various emission reduction materials and technologies based on release mechanism of asphalt VOCs‧ There are no comprehensive research and intuitive comparison on emission reduction materials due to the differences between quantitative standards for emission reduction effects‧ This paper summarizes the current research status of asphalt VOCs emission reduction, including the development history of emission reduction technology and reduction mechanism of various asphalt VOCs emission reduction materials mainly based on inhibitors, warm mixing agents and flame retardants‧ In addition, the emission reduction effects of different emission reduction materials are compared and the improvement trend research direction of new and efficient asphalt VOCs reduction technology and materials are proposed to achieve green and low-emission construction‧ Finally, around the environmental protection theme of VOCs emission reduction, this study also put forward the prospect of full life cycle emission mechanism and feasibility of efficient composite materials design to support the urgent need for green transport.

The intermittent distribution of localized turbulent structures is a key feature of the subcritical transitions in channel flows, which are studied in this paper with a wind channel and theoretical modeling. Entrance disturbances are introduced by small beads, and localized turbulent patches can be triggered at low Reynolds numbers (Re). High turbulence intensity represents strong ability of perturbation spread, and a maximum turbulence intensity is found for every test case as Re ≥ 950, where the turbulence fraction increases abruptly with Re. Skewness can reflect the velocity defects of localized turbulent patches and is revealed to become negative when Re is as low as about 660. It is shown that the third-order moments of the midplane streamwise velocities have minima, while the corresponding forth-order moments have maxima during the transition. These kinematic extremes and different variation scenarios of the friction coefficient during the transition are explained with an intermittent structure model, where the robust localized turbulent structure is simplified as a turbulence unit, a structure whose statistical properties are only weak functions of the Reynolds number.

In this Letter, the velocity structures and the extension behavior of localized turbulent bands in channel flows are measured by particle image velocimetry in a plane parallel to the walls and are analyzed by comparing with direct numerical simulations at low Reynolds numbers. It is illustrated that the convection velocity of the band head (band's downstream end) is not determined by the formation and propagation of low-speed streaks but by a high-speed "hat"shaped region near the band head. This "hat"region travels downstream obliquely like a solitary wave and leaves newly generated low-speed streaks to travel slowly in the spanwise direction, leading to the head extension of turbulent bands.