摘要：
Asphalt pavement is inevitably exposed to sunlight and different water environment during the service life, and the environment changes have caused the asphalt to be aged under the more complex environment such as more severe ultraviolet (UV) radiations, acid rain, or deicing salt conditions, however, the ageing mechanism and impact of coupled water and UV radiation is still not clear. In order to evaluate the coupling impact of different water environment (salt, acid) and UV radiation on the rheological properties and microstructure of asphalt material, short-term aged Rolling Thin Film Oven (RTFO) samples were further aged in UV and various water environment to simulate the UV and acid rain or salt condition, the Dynamic Shear Rheological (DSR) test, Bending Beam Rheological (BBR) test, SARA (saturates, aromatics, resin, and asphaltene) four-component analysis test and Fourier Transform Infrared Spectrometer (FTIR) tests were carried out. The results show that the coupling of different water environments and UV radiation accelerated the ageing of asphalt, which leads to the decrease of saturated, aromatic and resin content, the increase of asphaltene, and the enhancement of absorption peaks of carbonyl and sulfoxide groups. The result also found that shorter wavelength UV radiation has a severer effect on asphalt ageing under the same UV radiation level.
摘要：
The characteristic of temperature field plays a significant role in the compaction quality of asphalt pavement, and various factors could affect the thermal parameters of the pavement and thus affect the distribution of the temperature field during compaction. In this research, the temperature transfer theoretical model and finite element model of asphalt pavement were established and calibrated through field measured data, and the sensitivity analysis was conducted to evaluate the factors affecting the temperature field, also a quantitative model of effective compaction time was established. The results found that the initial rolling temperature and layer thickness affected the overall temperature field during compaction, and the wind speed and air temperature mainly affected the temperature field of the upper layer of hot mix asphalt (HMA). The change of the underlying layer temperature mainly affected the temperature field of the bottom of the layer. The established quantitative model provided a mathematic tool for the guidance of the field compaction process. (C) 2020 Elsevier Ltd. All rights reserved.
摘要：
The Phosphorus Slag (PS) is a yellow phosphorus industry by-product which could lead to land and water pollutions if not properly processed, researchers have found that the PS micropowder can be used as an additive for asphalt pavement applications. However, the difference in surface properties of PS micropowder could result in the variation of pavement performances. This research carried out the PS surface modification technique and evaluated the optimum surface modifier among five different types of modifiers and analyzed the optimum modification time, temperature and content of PS additives. And the Dynamic Shear Rheological Test (DSR) and the Bending Beam Rheology (BBR) tests were carried out on the original, short-term aged and long-term aged asphalt samples to evaluate the impact of PS and surface modifier on the performance of asphalt. The results found that phosphate monoalkoxy titanate (TM-P) has better wettability and oil absorption performance on PS micropowder among the five modifiers under the evaluated conditions. And the best modification time is 35 min at the temperature of 70 t, and the optimum amount of TM-P is 2.5%. The Scanning Electron Microscope (SEM) tests confirmed that the TM-P improves the dispersibility and compatibility of PS micropowder in asphalt, reduces the aging sensitivity of PS micropowder modified asphalt, improves the aging resistance and high-temperature rutting resistance, and also helps to improve the fatigue resistance and low-temperature cracking resistance of PS asphalt. (C) 2020 Published by Elsevier Ltd.
摘要：
Although the same compaction degree is achieved in practice, asphalt mixture samples prepared by different compaction methods often have different mechanical properties. In this paper, the air void content (AV) and distribution of aggregates and asphalt mortar in the process of asphalt mixture compaction are traced to capture the meso structural change characteristics of asphalt mixture during compaction. Using the discrete element method (DEM), a numerical technique is developed to simulate the laboratory compaction by taking into account the critical aggregate size and boundary effect. First, the critical aggregate size (CAS) is determined by the 2D and 3D binary particle assembly. Second, DEM simulations of both the Marshall impact compaction (MIC) and static compaction (SC) methods are conducted by the mass-wall and servo boundary, respectively. Third, the applicability of the 2D model is demonstrated through laboratory tests and numerical calculations. Finally, the distribution of aggregates and asphalt mortar are displayed and analyzed. The results show that the variation of CAS presents linear growth approximately with the increase of coarse particle size, less affected by the boundary. The primary control sieve (PCS) is applicable to separate the coarse and fine particles in the 3D assembly, but the CAS is around 0.195 for the 2D assembly, which is obviously less than the PCS. It is verified by two compaction methods and two mixture gradations that the DEM simulation is an effective way to evaluating the compacting effects of the compaction process. By double-sided hammering, coarse aggregates are moved to accumulate more closely, thus the coordination number at the bottom increases. Although a dense specimen can be achieved by compaction method, the size distribution of particles is still uneven in horizontal direction, since the position of large size particles (>16 mm) is difficult to be changed in the compaction process. (C) 2019 Elsevier Ltd. All rights reserved.
摘要：
Bitumen aging can lead to the deterioration of asphalt pavement performance, shortening the service life of road. In order to solve the problem that current studies on the ultraviolet (UV) aging of bitumen either ignore the effects of natural environmental conditions or only consider the effects of water. In this study, different aqueous media and UV coupled simulated aging tests were carried out on virgin bitumen and styrene butadiene styrene (SBS) modified bitumen in a UV environment chamber. The combination of macroscopic performance tests and microstructure tests was used to analyze the physical, rheological, and microstructure changes of virgin bitumen and SBS modified bitumen after The film oven test (TFOT) aging and UV aging in different environments (UV, UV + Water, UV + Acid, UV + Salt). Dynamic shear rheometer (DSR) results indicated that UV aging results in the increase of rutting factor and the improvement of rutting resistance at high temperature. The Fourier transform infrared spectrum (FTIR) results illustrated that the bitumen would be oxidized and SBS would be degraded under ultraviolet radiation. The four-component analysis test results showed that light component migrated to the heavy component during the aging process. Moreover, water will aggravate the UV aging of bitumen, and the presence of acid or salt worsens ultraviolet aging.
摘要：
This research carried out the NO2 degradation performance and asphalt pavement performance of SBS modified asphalt with different content (0%, 1%, 2%, 5%, 10%) of nano-TiO2, and the impact of cationic surfactant were evaluated as well. The nano-TiO2 modified asphalt was prepared for Dynamic Shear Rheometer (DSR) test, Bending Beam Rheometer (BBR) test, Rolling Thin Film Oven Test (RTFOT) and Pressure Aging Vessel (PAV) test. And the high temperature performance, low temperature performance and aging properties were evaluated. Results show that the nano-TiO2 increased the rutting resistance of asphalt in high-temperature especially when the content increased from 0% to 1%, and it did not have a significant impact on low temperature cracking resistance. Secondly, this research developed an innovative photo-reactive and measuring system, and simulated the NO2 degradation environment based on field data of varies typical roadway sections. Then, this research conducted photo-catalytic degradation test of NO2 for asphalt mixture with 5% nano-TiO2 content. The analysis shows that there are reversible reaction between NO2 and N2O4, and results indicated that the asphalt mixture has exhibited NO2 degradation effects. This research provided a deep understanding for the road performance and engineering application of nano-TiO2 modified asphalt mixture.
摘要：
TiO2 pillared montmorillonite (T/M) modifiers have been studied to alleviate the aging of asphalt pavement and degrade automobile exhaust, but the photocatalytic activity of ordinary TiO2 is not good enough. In this study, in order to improve the photocatalytic performance of T/M, different metal (Ce, Cu, Fe) doped modifiers were prepared based on T/M. Metal doped TiO2 pillared montmorillonite was prepared by the sol-gel method. The modifier was characterized by X-ray diffraction (XRD) and an Ultraviolet visible (UV-Vis) spectrophotometer. The results show that TiO2 with different metal ions successfully entered into the layer of organic montmorillonite (OMMT) to form a pillared structure. Compared with the undoped TiO2 pillared montmorillonite (T/M), the optical absorption edge of the metal doped TiO2 pillared montmorillonite has an obvious red shift. In addition, the influences of the different content of modifiers on the properties of the original bitumen and catalytic capacities for automobile exhaust were also investigated. The results show that Ce doped TiO2 (Ce-T/M) pillared montmorillonite has the best improvement in high temperature performance and ultraviolet (UV) resistance of bitumen. In the experiment of automobile exhaust degradation, the degradation law of NO and HC showed Cu-T/M > Ce-T/M > Fe-T/M > T/M. These three kinds of metal ions can effectively improve the photocatalytic degradation efficiency of T/M.
