Abstract
The aging of bitumen is detrimental to the durability and service life of asphalt pavement. Previous studies found that bitumen was suspected to be aged by not only thermal oxidation but also solution immersion. This research aims to compare the effect of thermal-oxidative aging and salt solution aging on bitumen performance. For this purpose, a thin film oven test (TFOT) and pressure aging vessel aging (PAV) were selected as thermal-oxidative aging, and 10% NaCl aging and 10% CaCl2 aging were selected as salt solution aging. The morphology, oxygen content, physical properties, low-temperature properties, and high-temperature properties of bitumen were analysed by employing scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS), physical tests, a bending beam rheometer (BBR), and a dynamic shear rheometer (DSR). Test results show that both thermal-oxidative aging and salt solution aging had similar influencing trends in the oxygen content, physical, low-temperature, and high-temperature properties of bitumen but had different changes in morphology. The aging degrees caused by four kinds of aging methods were obtained based on the summed values of the absolute aging factor of all parameters: PAV > 10% NaCl > TFOT > 10% CaCl2. The conclusions could provide a theoretical basis to establish a standard for the solution aging of bitumen.
Highlights
The aging of asphalt pavement is among the most concerning issues inducing pavement distresses, such as fatigue cracking, thermal cracking, and low-temperature cracking
Bitumen aged by thermal-oxidative aging (TFOT and pressure aging vessel aging (PAV)) showed different phenomena on the morphology of bitumen compared to salt solution aging
The sum of absolute values of all aging factor (AF) of salt solution aged bitumen is close to that of thin film oven test (TFOT) aged bitumen, which indicates that the influence of salt solution aging on bitumen performance is comparable to that of TFOT aging
Summary
The aging of asphalt pavement is among the most concerning issues inducing pavement distresses, such as fatigue cracking, thermal cracking, and low-temperature cracking. These distresses would reduce the service life of the pavement and driver’s comfort [1]. The aging of bitumen is attributed to four factors: solar radiation, moisture, time, and temperature [4]. Among three aging modes on bitumen, thermal-oxidative aging is the most mature and studied by a large number of researchers, and solution aging is a new formation during recent years [7,8]. A comparison with thermal-oxidative aging would promote the customization of the specifications of solution aging of bitumen
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