The NO_x degradation performance of nano-TiO₂ as a coating material for the road environment was evaluated in this research. The nano-TiO₂ coating materials for both road surface and roadside were prepared by using anatase nano-TiO₂, activated carbon powder, silane coupling agent and deionized water. The impact of varying amounts of coating material and silane coupling agent were evaluated. The road environment of NO_x degradation was simulated by the photocatalytic test system designed by the research team. For the road surface coating, the photocatalytic degradation experiments of NO under different radiation intensities were carried out. The results show that the material has good photocatalytic degradation performance, and the proper amount of silane coupling agent can enhance the bonding performance of the material and asphalt mixture. For the roadside coating, sodium dodecylbenzene sulfonate was selected as the surfactant to carry out the photocatalytic degradation experiment of NO₂ with different dosages of surfactant. The results showed that when the mass ratio of nano-TiO₂ and surfactant was about 1:2, the catalytic degradation effect of the material was the best.

This paper proposes a simple method for studying the evolution of particle breakage. A two-parameter statistical model is first proposed to describe the distribution of new particles generated from breakage of an initially uniformly graded sample. A Markov chain model is then proposed to describe the particle size evolution of non-uniformly graded samples. The two-parameter statistical model is shown to be able to capture different breakage patterns such as asperity breakage and particle splitting observed during breakage of uniformly graded samples. In the Markov chain model, it is shown that the concept of ‘effective breakage probability’, proposed to define the relative breakage extent of the whole sample, is comparable to a well-established breakage index in the literature. Both models are successfully validated against experimental data, where the characteristics of the model parameters and the engineering implications are discussed.

Crater depth is a vital issue in dynamic compaction (DC) because it is a controlling parameter in DC and a characterization index of soil properties. A continuous mathematical model capturing the time-domain process of tamper displacement is presented in this paper. The model is simple and the parameters involved are easy to obtain. It was found that the accumulated crater depth increases but its increment in the crater depth decreases with multiple impacts. Three groups of large-scale DC tests with 10,000 kN∙m were conducted to evaluate the performance of the proposed model. The results showed that the proposed model captures the typical trends in the tamper displacement of single and multiple impacts. In addition, a concept of the crater depth ratio is proposed based on the proposed model, and the concept is used to evaluate the efficiency of DC and to predict the optimum tamping number of DCs.

Transverse thermoelectric performance of the artificially tilted multilayer thermoelectric device (ATMTD) is very difficult to be optimized, due to the large degree freedom in device design. Herein, an ATMTD with Fe and Bi₂Te_2.7Se_0.3 (BTS) materials was proposed and fabricated. Through high-throughput calculation of Fe/BTS ATMTD, a maximum of calculated transverse thermoelectric figure of merit of 0.15 was obtained at a thickness ratio of 0.49 and a tilted angle of 14°. For fabricated ATMTD, the whole Fe/BTS interface is closely connected with a slight interfacial reaction. The optimizing Fe/BTS ATMTD with 12 mm in length, 6 mm in width and 4 mm in height has a maximum output power of 3.87 mW under a temperature difference of 39.6 K. Moreover the related power density per heat-transfer area reaches 53.75 W·m⁻². This work demonstrates the performance of Fe/BTS ATMTD, allowing a better understanding of the potential in micro-scaled devices.

Urban pavement runoff has become an important pollution source endangering the quality of urban water. This paper analyzed the characteristics of particle size distribution of road-deposited sediment (RDS). The variation of pollutants with RDS content is presented. Based on continuous sampling of runoff, the variation between pollutant concentration and rainfall characteristics is revealed. The results show that each particle group shares similar content except for the group smaller than 0.075 mm. However, the smaller particles have a stronger ability to adsorb heavy metals (Zn, Pb, Cu), and a weaker ability to adsorb chemical oxygen demand (COD). The concentrations of different pollutants have different relationships with rainfall and runoff time. The concentration of suspended solids (SS) decreases steadily with runoff time, while the concentration of heavy metals increases first and then decreases. The first 30 minutes of runoff is the best time to treat heavy metals and SS. The five-day biochemical oxygen demand (BOD5) and total petroleum hydrocarbons (TPHs) concentration are mainly affected by rainfall intensity. The result presented in this paper may provide a useful reference for the treatment of pavement runoff pollution.

Phosphogypsum (PG), as a by-product of the production of phosphoric acid, faces the problems of large annual output and difficult treatment. There is a large demand for fillers in the process of road paving, which may be an effective method for the utilization of PG resources. In this study, three proportions of phosphogypsum–lime–fly ash (PLF) mixture were designed, first, according to orthogonal tests. The comprehensive performance of the PLF mixture was tested by the compression rebound modulus test, unconfined compressive strength test, flexural tensile strength test, dry shrinkage test, and temperature shrinkage test, respectively. The results show that adding crushed stone to the PLF mixture can effectively improve the compression rebound modulus, unconfined compressive strength, and flexural tensile strength. The high content of PG in the mixture can also improve the dry shrinkage and temperature shrinkage properties of the mixture. According to the road layer requirements, the optimum proportion of the PLF mixture is recommended, which may benefit the road construction and PG resources.