Characterize Phenolic Compounds in Olive Pomace and Antioxidant Performance of Asphalt with Pomace

Abstract: The use of antioxidant additives is one of the effective technologies to retard asphalt aging and extend the service life of asphalt pavement. This study aims to characterize the phenolic compounds in the processed olive pomace (POP) and evaluate the recycling of POP as a bio-based antioxidant additive to modify asphalt binders. The total phenolic content, individual phenolic compounds, and 2,2’-diphenyl-1-picrylhydrazyl radical and ferric reducing antioxidant power assays were performed to characterize the antioxidant activities of POP. The antioxidant performance of POP-modified asphalt binders and the control binder was characterized and compared using chemical and rheological aging indexes after laboratory accelerated aging tests and natural weather aging tests. The adhesion between POP-modified asphalt and aggregates before and after long-term laboratory aging was assessed using the Vialit test. The results showed that the heating treatment of POP would not compromise its antioxidant activities and may even slightly increase its radical scavenging activity due to the cell wall destruction and release of bound phenolics. The POP-modified asphalt binders had slower growth rates of carbonyl index values than the control binder under pressurized aging vessel (PAV) tests. The phenolic compounds in POP, such as oleuropein and hydroxytyrosol, could work as free radical scavengers to retard the aging of asphalt binders subjected to thermal oxidation. The POP-modified asphalt binders also exhibited improved adhesion with aggregates compared with the control binder before and after the long-term laboratory aging. Thus, POP is a promising bio-based antioxidant additive used in asphalt paving materials.