Investigation of binder aging level in short-term-aged PMA mixture with different anti-stripping additives

As an anti-stripping additive (ASA) of hot-mix asphalt (HMA) mixture, the hydrated lime (HL) has been widely used for many years. Conversely, many brands of liquid anti-stripping additive (LA), which properly provide the anti-stripping function, are also used. HL is known to provide anti-aging functions by retarding age-hardening of the binder in addition to ASA functions. However, the LA was not much evaluated or reported regarding anti-aging function. Since the retardation of binder age-hardening is the foundation of many other beneficial functions of asphalt pavements, it is important to investigate whether the anti-aging function is provided by the LA as well. Therefore, this study investigated the anti-aging effects of HL and two liquid additives in SBS-modified SMA mixes in terms of absolute viscosity estimated from large molecular size (LMS) measured by the gel-permeation chromatography (GPC). It was found that two LAs did not provide any retardation of age hardening effects in polymer-modified asphalt mixes, compared with the binder of the mixes with HL and without any ASA. The PMA in one of the LAs showed a significantly higher age-hardening than the one without any ASA. While HL reacted as a significant age-hardening retarder of PMA in SMA mixes. Therefore, it was concluded that there was significant difference in oxidation level due to the use of different ASAs used in this study.