Effect of Recycling Agents on the Resistance of Asphalt Binders to Cracking and Moisture Damage

Abstract

This study examined the effect of five chemically different recycling agents on the long-term performance and moisture sensitivity of modified aged asphalt binder. A control base binder was made from 35% virgin binder and 65% binder exposed to extended laboratory aging. Samples of this control base binder were modified by a recycling agent in one of five categories: paraffinic oil, aromatic extracts, naphthenic oil, triglycerides/fatty acids, and tall oil. Then these modified binders and the control base binder were evaluated under each of four different conditions: no aging, standard aging, extended aging, and severe aging. The resistance to cracking at low and mid-range temperatures was determined using a bending beam rheometer and a dynamic shear rheometer. In addition, the Wilhelmy plate test was performed on the unaged binders to estimate the binders’ resistance to moisture damage. The results indicated that the samples modified with recycling agents that contain carbonyl, hydroxyl, and sulfonyl groups did not comply with the low-temperature cracking criterion (m-value) after the extended aging process. Samples modified with recycling agents containing paraffinic and naphthenic oils, which have a high saturate content, showed the weakest long-term performance, while the performance of the aromatic extract recycling agent was superior, even after the extended aging process. The Wilhelmy plate test showed that recycling agents based on triglycerides/fatty acids or tall oil decreased both the cohesive and adhesive strengths of the samples more than other recycling agents, which might be related to the presence of a hydroxyl group in their structures.