Abstract
In between thermal-oxidative (heat and oxygen) and photo-oxidative (ultraviolet irradiation and oxygen) aging process of bitumen, photo-oxidative aging mainly depends on the optical properties of the asphalt binder. The higher the reflection (or the lower the absorption of the binders), the better the pavement serviceability. The literature review indicates that there is limited research conducted on the optical properties of the binder with wax additives. In this paper, the optical properties of commonly used binders (PG 64-22, Rubber modified binder, and SBS modified binder) containing wax additives (LEADCAP and Sasobit) were investigated using UV-Vis spectrometer. The result of this study showed that (1) the addition of modifiers (crumb rubber and SBS) with the base binder slightly increases the absorption of the binder; (2) the binder types and aging level have significant contribution on optical properties; (3) in general, the aged binders were observed to have higher reflectivity compared to the unaged binders; and (4) the addition of wax additives is observed to have a significant effect on the optical properties.
Highlights
Bitumen has been extensively used as a binder in road construction [1]
Viscosity of asphalt binders at high temperatures is considered as an important property because of its ability to be pumped through an asphalt plant and workability. e viscosity test was conducted at two testing temperatures (135°C and 120°C). e addition of SBS and crumb rubber is found to increase the viscosity of PG 64-22, as expected
E stiffness and m-value of the binders with and without wax additives were measured on the aged binders using bending beam rheometer (BBR) tests at − 12°C. e Superpave standards determine that samples can fail at a given test temperature when the stiffness is greater than 300 MPa or with an m-value lower than 0.300 [22]. e decrease in stiffness reduces the tensile stress in the asphalt binder, which decreases the chance of low-temperature cracking. e addition of crumb rubber reduced the binder stiffness. e binders modified with Sasobit exhibited highest stiffness within each binder type. e addition of LEADCAP is observed to have significant effect on reducing the stiffness of the binders (6%, 7%, and 3% reduction were achieved for PG 64-22, polymer modified asphalt (PMA), and crumb rubber modified (CRM) binder, respectively)
Summary
Bitumen has been extensively used as a binder in road construction [1]. Like other organic materials, bitumen is prone to become fragile and stiff due to exposing to ultraviolet (UV) light, oxygen, and heat during storage, mixing, transport and laying down, as well as in service life [2,3,4]. e absorption of UV light from the sun degrades the bitumen properties, and the effects are different depending upon the binder type. E absorption of UV light from the sun degrades the bitumen properties, and the effects are different depending upon the binder type. UV radiation and oxidation affect the upper layer of the pavement surface and make the bitumen more brittle and hard, which would lead to reduction in long-term performance, at low temperature, and shorten the pavement life. E effects of UV irradiation on bitumen aging were ignored in early researches because solar radiation only affects the upper layers of pavement. Antioxidants, light stabilizers/ultraviolet absorbers, montmorillonite, phosphorus compounds, carbon black, thermochromic materials, and layered silica were implemented to improve the UV and oxidation aging resistance of bitumen [4, 5, 8,9,10,11]
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