Investigating the effect of antioxidants on aging behavior of asphalt binders: A chemo-rheological testing and characterization

Abstract

Antioxidants (AOs) are additives that can control asphalt oxidation and extend pavement service life. However, the final product may fail to provide the desired long-term performance and in-service aging mitigation without a comprehensive characterization of the AO and asphalt binder blends. This study employed rheological and chemical methods to characterize three AOs—butylated hydroxytoluene (BHT), zinc diethyldithiocarbamate (ZDEC), and ethylenediaminetetraacetic acid (EDTA)—incorporated at two dosage levels into two performance grade (PG) binders (PG 64–34 and PG 64–22). The obtained binder properties and indices at different aging levels, temperatures, and testing conditions were used to evaluate the effectiveness of these AOs in slowing the aging progression. The Glover-Rowe parameter showed that 4 % ZDEC could extend the aging time of the PG 64–34 binder in a pressure aging vessel from 60 h to 124 h before meeting the significant block cracking threshold. Additionally, 2 % ZDEC resulted in a one-grade change on the low temperature PG of the PG 64–22 binder, bumping down the resultant material to PG 64–28. On the other hand, S-value and m-value parameters from the bending beam rheometer test indicated that low-temperature cracking resistance could be reduced after BHT and EDTA modification. Data also showed that increasing EDTA dosage from 0.1 % to 2.0 % could diminish antiaging capability. These findings were supported by the carbonyl and sulfoxide indices obtained from Fourier-transform infrared spectroscopy. The AO modification efficacy of ZDEC was further validated using a third binder (PG 64–22) sourced from Virginia. Overall, BHT and EDTA were not nearly as favorable for use in asphalt binders as ZDEC.