Abstract
Properties of asphalt mixtures after ageing are fundamental parameters in determining long-term performance (e.g. durability) of these materials. With increasing popularity of reduced temperature mixtures, such as warm-mix asphalt, WMA, the question remains how a reduction in short-term ageing affects the properties after long-term ageing of bituminous materials. This paper aims to improve our understanding of the effect of asphalt manufacturing temperature on ageing and the resulting mechanical properties of bituminous binder by studying the effect of short- and long-term ageing of different bitumen samples as a function of short-term ageing temperatures. For this purpose, round robin experiments were conducted within the RILEM technical committee (TC) 252 chemo-mechanical characterisation of bituminous materials by 10 laboratories from 5 countries using four binders of the same grade (70/100 pen) from different crude sources. The short-term ageing was carried out using the standard procedure for rolling thin film oven test (RTFOT), but varying the temperatures. Long-term ageing was carried out using the standard procedure for pressure aging vessel (PAV) in addition to RTFOT. For the mechanical characterisation, rheological data were determined by using the dynamic shear rheometer (DSR) and conventional tests, with needle penetration and softening point using the ring and ball method. The results show that although different short-term ageing temperatures showed a significant difference in the mechanical properties of the binders, these differences vanished after long-term ageing with PAV.
Highlights
As an organic material, bitumen undergoes changes in its mechanical characteristics, chemical composition and microstructure due to environmental effects over its lifetime (Glotova, Gorshkov, Kats, Shapiro, & Yureva, 1980; Lee, Tia, Ruth, & Page, 1997; Mills-Beale et al, 2012; Yao, Dai, & You, 2015)
The analysis of basic properties with penetration value at 25°C and softening point temperature has shown a difference after rolling thin film oven test (RTFOT) with different short-term ageing temperatures
This difference vanishes completely for the penetration value and to a lesser degree for the softening point after pressure aging vessel (PAV) ageing
Summary
Bitumen undergoes changes in its mechanical characteristics, chemical composition and microstructure due to environmental effects over its lifetime (Glotova, Gorshkov, Kats, Shapiro, & Yureva, 1980; Lee, Tia, Ruth, & Page, 1997; Mills-Beale et al, 2012; Yao, Dai, & You, 2015). With regard to chemical composition, a shift within the SARA (saturates, aromatics, resins and asphaltenes) fractions can be observed with an increasing amount of asphaltenes and decreasing amount of aromatics over time (Hofko, Eberhardsteiner, Fussl, & Grothe, 2016; Lu & Isacsson, 2002) These changes are generally summarised under the term “ageing”. In the case of hot mix asphalt, short-term ageing occurs during asphalt mix production, transport and compaction at the construction site, all of which happens within hours. It is characterised by relatively high temperatures ( > 130°C) and high oxidation rates. Ageing of bitumen has a crucial effect on the durability of asphalt mixtures (Lu, Redelius, Soenen, & Thau, 2011), since stiffer and more brittle binders make an asphalt pavement more prone to cracking
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