Application of Recycled Asphalt Shingles in an Asphalt Mix as a Compaction Aid

Recycled asphalt shingle (RAS) is a recycled material with 25% binder on average. Its inclusion in new asphalt mixes potentially can decrease the use of virgin binder and the construction cost, while also reducing RAS disposal and preserving the environment. However, the high level of oxidized binder in RAS presents several challenges. The use of RAS often is limited to 5% because it has been found to adversely affect the cracking performance of the mix. Achieving adequate compaction density during asphalt mix construction is crucial for optimal pavement performance. Agencies and contractors continuously seek effective methods to achieve optimal compaction. This study proposes a novel approach that utilizes RAS as a compaction additive in asphalt mixes. It capitalizes on the fact that RAS binder is active at production and compaction temperatures, but minimally active at service temperatures. The RAS was introduced to as-designed mixes in proportions of as much as 5% of the mass of mixes, which are referred to as RASAID mixes, and its impact on the volumetric properties and performance parameters of control loose mixes was analyzed. The compactability of the mix was enhanced because the air voids were reduced by 50% with 5% inclusion of RAS. It was found that the use of RAS as compaction aid has a statistically insignificant impact on the laboratory cracking and rutting performances. This method has potential to improve the compaction of asphalt mixtures, which can lead to increased pavement life and more-widespread and -effective use of RAS.