Surfactants in Aged Asphalt and Impact μ on Moisture Susceptibility of Laboratory-prepared Mixes

ABSTRACT Short-term aging (rolling thin-film oven test) of an asphalt binder resulted in the production of surfactants (surface-active compounds), while long-term aging (pressure aging vessel test) of asphalt binders resulted in the production of not only surfactants but also strong acids. The strong acids were identified as being sulfonic acids. It was proposed that the generation of surfactants and/or sulfonic acids in asphalt binder would promote moisture damage in asphalt-aggregate mixes. The surfactants could act as a detergent and emulsify components of the mix, and sulfonic acids could attack the aggregate surface, thus, disrupting the asphalt-aggregate interface. A model compound, p-dodecylbenzenesulfonic acid, which incorporates these two structural features, was used as a modifier in several different mixes. Briquets fabricated from the modified mixes were tested for moisture susceptibility using the freeze-thaw pedestal test. It was observed that those mixes, which were originally not susceptible to moisture damage, were now susceptible. It was also noted that the addition of lime to the aggregates prior to the fabrication of the briquets counteracted the influence of p-dodecylbenzenesulfonic acid.