Zhengang Feng

Effect of aging on the morphology of bitumen by atomic force microscopy.

Effect of aging on the morphology of bitumen was investigated. Two bitumens were aged according to the thin film oven test (TFOT), pressure aging vessel (PAV) test and ultraviolet (UV) radiation, respectively. The morphology of the binders before and after aging was characterized by atomic force microscopy. The physical properties and chemical compositions of the binders were also measured. The results showed that aging affected the bitumen morphology significantly. Aging increased the overall surface stiffness of the bitumen and made the bitumen surface more solid‐like. The extent of these changes was dependent on aging conditions. TFOT decreased the contrast between the dispersed domains and the matrix, which contributed to the single‐phase trend of the binders. The effect of PAV aging on morphology of the binders was dependent on the base bitumen. In one case, it further accelerated the single‐phase trend of bitumen in comparison with that after TFOT. In the other case, it caused the phase separation of bitumen. In both cases, PAV aging increased the surface roughness of the binders obviously. As a result of UV aging, the contrast between the matrix phase and dispersed phase was increased due to the difference in sensitivity to UV radiation of the bitumen molecules, which caused or further promoted the phase separation in the binders. Regardless of the aging procedure carried out, a strong correlation was observed between the changes in morphology and physical properties as well as chemical compositions of the binders before and after aging.

The Physical Properties and Photostability of Bitumen with Different Ultraviolet Absorbers

Effects of different ultraviolet (UV) absorbers (octabenzone and bumetrizole) on physical properties and photostability of bitumen were investigated. Thin-layer chromatography with flame ionization detection was applied to analyze the likely mechanism of UV absorber on chemical transformation and ageing properties of bitumen. Results indicate that ductility of bitumen is significantly enhanced by addition of small amount of UV absorbers, especially for the addition of octabenzone, which is mainly attributed to the increase of aromatics content of bitumen. The influence of UV absorbers on photostability of bitumen is dependent on the origin of bitumen and type of UV absorber. Bitumen from different origins shows specific selectivity for different UV absorbers.

Effect of Layered Double Hydroxides (LDHs) on Aging Properties of Bitumen

Layered double hydroxide (LDH) modified bitumen was prepared via melt blending. The effects of LDHs on the physical properties and aging properties of bitumen were studied. The influence of LDHs on the chemical structure of bitumen before and after a thin film oven test (TFOT) and an ultraviolet (UV) radiation test was evaluated by means of Fourier transform infrared (FTIR) spectroscopy analysis. The results show that with increasing LDH content, the softening point and viscosity of bitumen gradually increase, whereas the ductility and penetration of bitumen decrease. LDHs can improve the ability of bitumen to resist TFOT aging and UV aging, especially when the LDH content is more than 3 wt. %. In the FTIR analysis, it is seen that LDHs can inhibit the oxidation of bitumen during TFOT and UV aging, resulting in smaller carbonyl and sulphoxide contents than in the pristine bitumen.

Performance Evaluation of SBS Modified Asphalt with Different Anti-aging Additives

The effects of three different types of anti-aging additives (bumetrizole, octabenzone, and tinuvin770) on the physical and rheological properties of styrene butadiene styrene (SBS) modified asphalt were investigated by means of conventional physical properties tests and dynamic shear rheometer (DSR) tests. In order to evaluate the aging properties of different anti-aging additive/SBS modified asphalts, the thin film oven test and ultraviolet (UV) radiation test were performed, and different aging parameters were compared. The results show that the penetration, ductility, and softening point are increased, whereas the viscosity is decreased, with the addition of different anti-aging additives. The DSR analysis indicates that anti-aging additives can enhance the elastic behavior and improve the thermal stability of SBS modified asphalt. Improvement in the thermal-oxidative aging properties of SBS modified asphalt can be achieved with the three different anti-aging additives, but the UV aging properties of anti-aging additive/SBS modified asphalts are dependent on the type of anti-aging additive. Of the three different anti-aging additives, tinuvin770 improves both the thermal- and the photo-oxidative aging resistance of SBS modified asphalt significantly.

The Relationship Between Colloidal Chemistry and Ageing Properties of Bitumen

Abstract The colloidal indices based on generic fractions, namely saturates (Sa), aromatics (Ar), resins (Re), and asphaltenes (As), were applied to evaluate the correlations between colloidal chemistry and ageing properties of bitumen. The results show that colloidal index Ip (value of Re/As) is positively correlated with penetration retention rate and ductility retention rate. The softening point increment is significantly influenced by colloidal index Is [value of As/(Sa + Ar + Re)]. The colloidal index Ic [value of (Ar + Re)/(Sa + As)] is obviously correlated with viscosity ageing index. Higher value of Ip and Ic, as well as lower value of Is, implies a better ageing resistance of bitumen.

A Study on Photo-thermal Coupled Aging Kinetics of Bitumen

The effect of photo-thermal coupled aging on the viscosity of bitumen was investigated at three different temperatures and three different ultraviolet (UV) light intensities. The photo-thermal coupled aging kinetic model of bitumen was put forward based on the viscosity of bitumen under different photo-thermal coupled aging conditions. In order to evaluate the extent of aging in bitumen, kinetic parameters based on the aging kinetic model were calculated and compared. The results reveal that UV radiation and heat play a coupled role in accelerating the aging process of bitumen. Photo-thermal coupled aging has a greater influence on the aging rate of bitumen than single factor aging. A higher aging temperature and UV intensity have a more pronounced effect on the photo-thermal coupled aging, which leads to an obvious acceleration of the aging reaction rate.

Ageing of polymer modified bitumen (PMB)

Abstract: To realize the ageing of polymer modified bitumens (PMBs) correctly is of great significance for academicians and technicians. This chapter begins by discussing the main causes of ageing for PMBs. It then illustrates simulative ageing methods, ageing performance and characterization, as well as the means for improving the ageing resistance of PMBs. The chapter finally outlines a short commentary on likely future trends and provides some sources of further information and advice.