Abstract
Layered double hydroxides (LDHs) are an ultravioletlight (UV)-resistant material. In this study, two types of LDHs (Mg-Al-LDHs and Zn-Al-LDHs) were applied to modify bitumen by melt-blending. The effect of ultraviolet aging on the rheology and chemistry of LDH-modified bitumen was studied by means of dynamic shear rheometer (DSR), thin-layer chromatography with flame ionization detection (TLC-FID), Fourier transform infrared spectroscopy (FTIR), and Ultraviolet-Visible (UV-Vis) spectrophotometry to reveal the mechanisms of action for LDHs and bitumen. The results showed that within the UV spectra (220–400 nm), the reflectance of Zn-Al-LDHs was larger than that of Mg-Al-LDHs. These two LDHs have different influences on the performance of bitumen. Mg-Al-LDHs had a more obvious influence on the physical and dynamic rheological properties of bitumen than Zn-Al-LDHs. Zn-Al-LDHs improved the UV-aging resistance of bitumen more. The reason can be that the reflectance of the Zn-Al-LDHs to the UV light is larger than that of the Mg-Al-LDHs. The Zn-Al-LDH-modified bitumen had more potential to improve the UV-aging resistance during the service life of asphalt pavement.
Highlights
Bitumen aging is one of the main reasons for asphalt pavement failure
Both Layered double hydroxides (LDHs) had a high reflectance to the light with a wavelength ranging from 200 to 800 nm
The zinc atoms of Zn-Al-LDHs can combine with an oxygen atom placed in between the layers to form zinc oxide (ZnO), which has a wider band gap (3.37 eV) than magnesium oxide (MgO)
Summary
Bitumen aging is one of the main reasons for asphalt pavement failure. Aging effects on bitumen are classified into two types: thermal-oxidative aging and light-oxidative aging. The thermal-oxidative aging refers to aging during mixing, storage, transportation, laying, and compaction of the mixture; the light-oxidative aging (UV aging) takes place during the service life of the asphalt mixture. Both of them can change the physical and chemical characteristics, causing the pavement to be stiff and brittle and shorten its service life [1,2,3]. To prevent bitumen from UV aging, one effective way is bitumen modification. Many modifiers have been investigated to improve the aging resistance of the bitumen, like organo-montmorillonite (OMMT), carbon black, etc. [4,5,6,7]
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