Guoxiong Wu’s research while affiliated with Chongqing Jiaotong University and other places

Bitumen’s evolution during aging includes oxidation, aromatization, chain scission, and carbonation, which alter bitumen’s properties of diffusivity and thermal conductivity and consequently bitumen’s healing capacity. To improve bitumen’s healing capacity after aging, there is a need to revitalize aged bitumen and restore its properties. This study studies the effect of ultraviolet (UV) aging on the healing capacity of bitumen containing different dosages of taconite tailings (a material with metal oxide as its main component). In addition, it examines whether the healing capacity of aged bitumen can be restored post-aging with the help of a rejuvenator made from waste vegetable oil. A healing index was used to measure the evolution of healing capacity in bitumen samples during aging and rejuvenation, using rheometry and spectroscopy. The study results show that exposure to UV aging increases the chemical aging index and rheological aging index, which makes bitumen stiffer and increases bitumen's complex modulus. This study further shows that taconite tailings accelerate the aging process of bitumen and increase its thermal conductivity. It was found that despite the negative effect of taconite tailings on bitumen aging, the presence of taconite tailings increased the healing capacity of bitumen. Results showed the healing capacity of bitumen containing taconite after being exposed to UV aging for 100 h and 200 h was up to 55.09% and 53.53% higher than that of bitumen without taconite, respectively. The samples with a higher content of taconite showed a higher healing capacity. Also all samples regardless of taconite dosage had higher healing capcity when rejuvnetor was present.

Based on the promoting effect of metal material on the healing property of asphalt binder, this study evaluated the merits of using taconite (an iron-containing filler from iron-mine tailings) to promote the healing performance of asphalt binder. Samples of asphalt binder modified with three different dosages of taconite were tested by a thermal conductivity (TC) device. The presence of taconite can provide TC values in asphalt mastic and thereby allow inductive heating to improve healing in asphalt pavement. Laboratory experiments were used to evaluate the healing property of asphalt mastic containing 10%, 20%, or 30% wt. taconite. The healing property was measured using a healing index based on the complex modulus. The TC values were tested using a new testing method, and then the relationship between TC values and healing performance was analyzed. In the range of content of taconite used in this study, thermal conductivity gradually increased with increased taconite. The results of the study showed that the presence of taconite improved the healing property of asphalt mastic. For healing time 900s, loading strain 5%, and degree of damage 50%, an increased dosage of taconite led to an increased healing property of modified asphalt binder, although the increase in the promoting effect on healing performance was not large. This study also evaluated the effect of several factors that influence the healing property of asphalt mastics. The content of taconite, the healing time, the loading strain level, and the degree of damage affected the healing performance of asphalt mastics modified by taconite. Since taconite is a by-product of mining iron-bearing sedimentary rock in which the iron minerals are interlayered with quartz, chert, or carbonate, our use of this so-called waste from mining and its application in construction is expected to promote resource conservation and recycling while enhancing sustainability in pavements.

This article presented the latest development of testing methods concerning surface textures and skid resistance of asphalt pavements. A review of the repeatability and harmonization of field-testing methods for macrotexture is outlined. Measuring methods of skid resistance both in lab and in situ are reviewed. The harmonization research on the laboratory and field-testing methods are summarized. The recent progress of skid-resistance modeling of asphalt pavement from well-known research work is summarized. This article also suggests a few key research directions. First, compared with macrotexture, standard testing procedures for microtexture also need to be established for uniform and comparable characterization methods. Second, the gap between lab test and field test for skid resistance should be bridged to realize more accurate estimation of pavement frictional properties in the phase of lab design. There is the need for the International Friction Index (IFI) model to be reevaluated when the data is acquired from testers installed with ribbed tires. Third, the accurate tire modeling of the dynamically frictional contact between tire and pavement still needs to be improved. The parameters of pavement textures, traffic volume, water, hydroplaning, temperature, and friction law on tire-pavement friction should be considered in depth in the modeling aspect.

This study examines the healing capacity of an asphalt mixture after the introduction of an iron-based additive (iron slag). It is hypothesized that iron-based additives can facilitate healing of asphalt pavement by enhancing the thermal conductivity of the asphalt pavement. To study the healing capacity of asphalt mixtures containing iron slag, specimens with various amounts of iron slag additive were prepared and tested using a semi-circular bending test. Healing tests were performed on samples with different crack lengths, which each crack length representing a specified damage degree. Infrared heating was used to condition each specimen to facilitate healing. The significance of factors such as the amount of iron slag, the healing temperature, the healing time, and the damage degree were studied through grey correlational mathematical analysis. Among the samples tested, the optimal healing content of iron additive was 2%, the optimal healing temperature was 60 °C. Samples with a damage degree of 30% recovered about 59% of their original structural strength. And the results from grey relational analysis showed that the extent of damage was the most influential factor, followed by healing temperature, dosage of iron slag, and healing time.

This study proposes a newly developed real-time testing system, namely, a tire-pavement dynamic friction analyzer (TDFA), to measure the dynamic friction coefficient between tire and pavement. Based on the self-developed TDFA, the friction coefficient between tire and pavement can be measured in real-time in the lab. A number of working conditions of tires were mimicked and tested. Subsequently, the effect of parameters such as tire load, tire pressure, actual tire-pavement contact area, tire speed, and slip ratio on pavement friction were investigated. It is found that there is a closely linear correlation between the actual tire-pavement contact area and the dynamic friction coefficient (DFC), and such correlation differs with the variation of pavement types. DFC usually has a negative linear relationship to tire speed. As slip ratio varies from 0% to 100%, the strongest correlation between DFC and Mean profile depth (MPD) can be found at the interval of 10%–15% slip ratio, which indicates that the pavement macrotexture also plays a role in the peak value of friction coefficient for the asphalt pavement. This testing method is very promising for the estimation of friction properties of pavement in the phase of lab mix design. It may also be used in the materials selection for pavement design.

The skid-resisting performance of pavement is a critical factor in traffic safety. Recent studies primarily analyze this behavior by examining the macro or micro texture of the pavement. It is inevitable that skid-resistance declines with time because the texture of pavement deteriorates throughout its service life. The primary objective of this paper is to evaluate the use of different asphalt pavements, varying in resilience, to optimize braking performance on pavement. Based on the systematic dynamics of tire-pavement contact, and analysis of the tire-road coupled friction mechanism and the effect of enlarging the tire-pavement contact area, road skid resistance was investigated by altering the elastic modulus of asphalt pavement. First, this research constructed the kinetic contact model to simulate tire-pavement friction. Next, the following aspects of contact behaviors were studied when braking: tread deformation in the tangential pavement interface, actual tire-pavement contact in the course, and the frictional braking force transmitted from the pavement to the tires. It was observed that with improvements in pavement elasticity, the actual tire-pavement contact area increased, which gives us the ability to effectively strengthen the frictional adhesion of the tire to the pavement. It should not be overlooked that the improvement in skid resistance was caused by an increase in pavement elasticity. This research approach provides a theoretical basis and design reference for the anti-skid research of asphalt pavements.