A new rejuvenator technology aims to improve the chemistry and service life of recycled asphalt pavement (RAP). The Invigorate additive, developed by Colorbiotics (Ames, Iowa; www.colorbiotics.com) based on Iowa State University research (www.iastate.edu), helps overcome issues with asphaltene aggregation and oxidation, which occur as RAP ages, and enables mixtures with more recycled content. “When asphalt ages, oxygen becomes permanently fused to the surfaces of asphaltene agglomerates. This accounts for a large part of cracking susceptibility and also impacts the ability of RAP to mix well with virgin asphalt concrete (AC) at a molecular level. Invigorate’s solvency breaks apart these agglomerates, and its chemical functionality permanently binds to the oxidized sites. The Invigorate-asphaltene complexes are more compatible with the virgin AC and are stabilized against reagglomeration,” explains Eric Cochran, professor of chemical and biological engineering at Iowa State. Produced from soybean-oil feedstock, Invigorate is unique in the marketplace in that it triggers chemical reactions within the RAP, rather than acting superficially, and is able to balance viscosity, solvency and reactivity to aggressively target oxidized asphaltenes, adds Cochran. Invigorate’s performance benefits mean that mixtures incorporating as much as 50% RAP can meet necessary specifications, greatly improving upon current industry-standard mixtures of 20–25% RAP.
While the sustainability benefits of increasing RAP content are clear, there are also durability considerations at higher RAP levels, says Dan Staebell, Colorbiotics’ asphalt business development manager. “Using RAP is environmentally and economically smart, but we have to be mindful of long-term durability when increasing to higher levels near 50%. This can be achieved and confirmed using the balanced-mix design approach. Contractors and officials across the U.S. are researching and understanding these tools and implementing them to assist in specification decisions,” says Staebell. Invigorate is currently undergoing a number of field trials across the U.S. wherein users have found the asphalt mixtures with higher RAP content very workable, even in colder conditions, according to Staebell.