Jianying Yu

Effect of ageing on rheological properties of storage-stable SBS/sulfur-modified asphalts

Oxidative ageing as an inevitable process in practical road paving has a great effect on the properties of polymer-modified asphalts (PMAs). In this article, the effect of short-term and long-term oxidative ageing on the rheological, physical properties and the morphology of the styrene-butadiene-styrene (SBS)- and storage-stable SBS/sulfur-modified asphalts was studied, respectively. The analysis on the rheological and physical properties of the PMAs before and after ageing showed the two major effects of ageing. On one hand, ageing prompted the degradation of polymer and increased the viscous behaviour of the modified binders, on the other, ageing changed the asphalt compositions and improved the elastic behaviour of the modified binders. The final performance of the aged binders depended on the combined effect. After ageing, the storage-stable SBS/sulfur-modified asphalts showed an obvious viscous behaviour compare with the SBS-modified asphalts and this led to an improved low-temperature creep property. The rutting resistance of the SBS-modified asphalts declined by the addition of sulfur due to the structural instability of the SBS/sulfur-modified asphalts. The rheological properties of the modified binders before and after ageing also depended strongly on the structural characteristics of SBS. The observation by using optical microscopy showed the compatibility between asphalt and SBS was improved with further ageing, especially for the storage-stable SBS/sulfur-modified asphalts.

Effect of aging on morphology of organo‐montmorillonite modified bitumen by atomic force microscopy

The morphology of unmodified and organo‐montmorillonite modified bitumens was investigated by atomic force microscopy. The influence of thin film oven test and ultraviolet aging on the morphology of the binders was also analysed. The atomic force microscopy results showed that bitumen displayed a ‘bee‐like’ structure and the dimension of the ‘bee‐like’ structures was decreased to some extent with the introduction of organo‐montmorillonite. Organo‐montmorillonite showed a better interaction with the dispersed domains in comparison with the matrix in bitumen, which led to an obvious increase in the contrast between the dispersed domains and the matrix in bitumen. Compared with the unmodified bitumen, the single‐phase trend in the organo‐montmorillonite modified bitumen could be effectively prevented during thin film oven test and ultraviolet aging, indicating its good aging resistance which was in accordance with changes in physical properties of the organo‐montmorillonite modified bitumen before and after aging.

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.

Effect of montmorillonite organic modification on microstructures and ultraviolet aging properties of bitumen

The effect of montmorillonite (MMT) organic modification on microstructures and ultraviolet (UV) aging properties of bitumen was investigated. The microstructures of MMT modified bitumen were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM), respectively. The binders were aged by UV radiation. The UV aging properties of MMT modified bitumen was studied by determining physical properties and AFM analysis. XRD and FTIR analyses show that the sodium montmorillonite (Na+‐MMT) modified bitumen forms a phase‐separated structure, whereas the organo‐montmorillonite (OMMT) modified bitumen forms an intercalated structure. After Na+‐MMT modification, the contrast between the matrix and the dispersed domains is inverted according to AFM analysis. However, this contrast inversion is prevented with the introduction of OMMT due to the good compatibility between the OMMT and the bitumen. As a result of UV aging, both viscosity aging index and softening point increment of OMMT modified bitumen are lower than that of the unmodified bitumen and Na+‐MMT modified bitumen. Furthermore, the association interactions and single‐phase trend in OMMT modified bitumen are further prevented in comparison with Na+‐MMT modified bitumen during UV aging, indicating the good aging resistance of OMMT modified bitumen after organic modification of MMT.

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.

Investigation of γ-(2,3-Epoxypropoxy)propyltrimethoxy Silane Surface Modified Layered Double Hydroxides Improving UV Ageing Resistance of Asphalt

γ-(2,3-Epoxypropoxy)propyltrimethoxy silane surface modified layered double hydroxides (KH560-LDHs) were prepared and used to improve the ultraviolet ageing resistance of asphalt. The results of X-ray photoelectron spectrometry (XPS) indicated that KH560 has been successfully grafted onto the surface of LDHs. The agglomeration of LDHs particles notably reduced after KH560 surface modification according to scanning electron microscopy (SEM), which implied that the KH560 surface modification was helpful to promote the dispersibility of LDHs in asphalt. Then, the influence of KH560-LDHs and LDHs on the physical and rheological properties of asphalt before and after UV ageing was thoroughly investigated. The storage stability test showed that the difference in softening point (ΔS) of LDHs modified asphalt decreased from 0.6 °C to 0.2 °C at an LDHs content of 1% after KH560 surface modification, and the tendency became more pronounced with the increase of LDH content, indicating that KH560 surface modification could improve the stability of LDHs in asphalt. After UV ageing, the viscous modulus (G’’) of asphalt significantly reduced, and correspondingly, the elastic modulus (G’) and rutting factor (G*/sin δ) rapidly increased. Moreover, the asphaltene increased and the amount of “bee-like” structures of the asphalt decreased. Compared with LDHs, KH560-LDHs obviously restrained performance deterioration of the asphalt, and helped to relieve the variation of the chemical compositions and morphology of asphalt, which suggested that the improvement of KH560-LDHs on UV ageing resistance of asphalt was superior to LDHs.

The Effect of Zinc Doped Mg-Al LDHs on Ultraviolet Aging Resistance of Asphalt

Effects of zinc doped Mg-Al layered double hydroxides (Zn-Mg-Al LDHs) and Mg-Al LDHs on physical and ultraviolet (UV) aging properties of asphalt were evaluated by conventional physical properties, dynamic rheological characteristics and Fourier transform infrared (FTIR) spectroscopy. The results show that the introduction of LDHs improves the UV aging resistance of asphalt. By comparison, Zn-Mg-Al LDHs are superior to Mg-Al LDHs in improving aging performance of asphalt, which is due to the more outstanding UV shielding of Zn-Mg-Al LDHs in comparison with Mg-Al LDHs, leading to a beneficial effect in improving UV aging performance of asphalt.