In this study, surface morphology, rheological and chemical properties were investigated of bitumen, which was modified by a composite of clay and fumed silica nanoparticles, and exposed to ultraviolet (UV) aging in laboratory. The volume fraction of the nanoparticles within the binder ranged from 1 to 3%, the temperature range considered was 30 to 70 °C. Surface morphology, rheological and chemical binder properties were analyzed using field emission scanning electron microscopy (FESEM), dynamic shear rheometer (DSR), and Fourier transform infrared (FT-IR) spectroscopy. It was found, that the bitumen modification through clay and fumed silica nanoparticles changed resulting binder properties significantly. The index of carbonyl and oxidation degree decreased, and the clay and fumed silica nanoparticles improved aging resistance to ultraviolet (UV) radiation considerably. The results indicate that the mechanical stability of the modified bitumen is very much driven by the specific concentration of clay and fumed silica nanoparticles.

In this paper, the effect of physical hardening and aging temperatures on the low temperature rheological properties of the asphalt binder is experimentally investigated and modelled. First, Dynamic Shear Rheometer (DSR) tests are performed from −30°C to 80°C on four virgin asphalt binders and the corresponding long-term aged binders, which were previously short-term aged at three different temperatures (123°C, 143°C, and 163°C). Master curves are generated to evaluate the impact of aging temperatures, while the effect of physical hardening is also addressed through a simple testing procedure. Then, Bending Beam Rheometer (BBR) tests are conducted under three different conditioning times (1 h, 24 h, and 72 h) for the same materials, followed by the calculation and comparison of creep stiffness, S(t) and relaxation parameter, m-value. In addition, the Huet model is fitted to the experimental data. Finally, the relationship between the time domain complex modulus based on DSR and the creep stiffness obtained with the BBR at different conditioning time is established, and the critical cracking temperatures are calculated and compared. Results indicate that physical hardening causes a significant increase in complex shear modulus and creep stiffness for DSR and BBR, respectively. This trend is remarkable between the first 60 minutes and 24 h while only a moderate contribution can be observed when conditioning time is extended. Linear correlations can be observed between the DSR and BBR results at different conditioning time. No particular storage time leads to equivalent E(t) master curves for BBR and DSR; the curve of 24 h seems to be a compromise in terms of experimental and time costs. In addition, the reduced aging temperature can significantly mitigate the effect of physical hardening, while only a slight improvement can be found in the aging properties of asphalt binders.

Asphalt binder ageing leads to significant changes in mechanical and physicochemical properties and often to premature cracking in asphalt pavements. A polymer-modified asphalt binder is repeatedly aged through laboratory techniques, i.e. rolling thin film oven test and pressure ageing vessel. The resulting properties of the aged binder are analysed using dynamic shear rheometer, Fourier transform infrared spectroscopy, atomic force microscopy and cryo-environmental scanning electron microscopy. Rheological, spectroscopic and macroscopic properties change progressively with the level of laboratory ageing. Surprisingly, this change shows approximately a linear trend. The first ageing step has the highest impact on the property change, whereas all the following ageing steps result in similar but reduced impact. Moreover, there is a strong interdependency between different mechanical and physicochemical properties. Hence, novel insights into the mechanics of asphalt binder ageing and into the search for ageing laws for asphalt binders.

The current experimental method used in Europe to characterise asphalt binder at high temperature is based on the Ring & Ball softening point. However, for modified binders it was demonstrated that such a method is unable to correctly characterise the material. In the present work, an alternative solution to determine the high-temperature properties of asphalt binders using the dynamic shear rheometer (DSR) is proposed: the Binder-Fast-Characterisation-Test (BTSV) (Bitumen-Typisierungs-Schnell-Verfahren, in German). Two parameters are identified for the rheological characterisation of asphalt binders: the temperature T_BTSV, which is related to the Ring & Ball softening point and is an indicator of the binder stiffness, and the phase angle δ_BTSV, which provides information on the degree of binder modification. These two key parameters are used to discriminate among the different asphalt binder domains in the high-temperature range.

Warm mix asphalt (WMA) is gaining increased attention in the asphalt paving industry as an eco-friendly and sustainable technology. WMA technologies are favorable in producing asphalt mixtures at temperatures 20–60 °C lower in comparison to conventional hot mix asphalt. This saves non-renewable fossil fuels, reduces energy consumption, and minimizes vapors and greenhouse gas emissions in the production, placement and conservation processes of asphalt mixtures. At the same time, this temperature reduction must not reduce the performance of asphalt pavements in-field. Low aging resistance, high moisture susceptibility, and low durability are generally seen as substantial drawbacks of WMA, which can lead to inferior pavement performance, and increased maintenance costs. This is partly due to the fact that low production temperature may increase the amount of water molecules trapped in the asphalt mixture. As a potential remedy, here we use fumed silica nanoparticles (FSN) have shown excellent potential in enhancing moisture and aging susceptibility of asphalt binders. In this study, asphalt binder modification by means of FSN was investigated, considering the effects of short-term and long-term aging on the rheological, thermal, and microstructural binder properties. This research paves the way for optimizing WMA by nanoparticles to present enhanced green asphalt technology.

In this paper, the combined effect of aging temperatures and cooling medium on the rheological properties of asphalt binder was experimentally investigated and evaluated. Two 70/100 penetration grade binders, which were part of the core materials used by the active RILEM committee CMB-252, were selected for this purpose. The materials were artificially aged to six different conditions, first with the Rolling Thin Film Oven Test (RTFOT) at three different temperatures (123°C, 143°C, and 163°C), and then, with the standard Pressure Aging Vessel (PAV). Next, temperature and frequency sweep (T-f-sweep) tests were performed on the entire set of materials by using the Dynamic Shear Rheometer (DSR) from −30°C to 80°C while low-temperature creep tests were conducted on the long-term aged asphalt binders with the Bending Beam Rheometer (BBR) devices in air and in ethanol, respectively. Then, the 2 Spring 2 Parabolic element 1 Dashpot model (2S2P1D) and Huet model were used to evaluate the rheological properties of asphalt binders based on the DSR and BBR results, respectively. Moreover, two parameters, crossover temperature, T_δ=45°, and the difference in critical temperature, ΔT_c, were used to evaluate the aging properties of the materials. Finally, the relationship between the time domain complex modulus based on DSR and the creep stiffness obtained with the BBR was established to investigate the effect of the cooling medium at low-temperatures. The results indicate that a temperature reduced process may lead to a mitigation of the short-term aging of asphalt binders, while a temperature reduction of only 40°C can result in a consistently milder long-term aging. In the BBR test, higher creep stiffness and smaller m-values can be observed in the air compared to ethanol. Huet and 2S2P1D models show that complex modulus and creep stiffness share the same core parameters only in the case of air. Based on the finding in this research, the temperature reduced mixing process and the use of air for BBR creep tests are recommended.