Potential use of recycled concrete aggregate (RCA) for sustainable asphalt pavements of the future: A state-of-the-art review

Abstract

With the continuous paving of roads around the world, the huge consumption of natural aggregate (NA) obtained through widespread excavation and extraction is now an inevitable part of highway construction. To alleviate this phenomenon, the use of recycled concrete aggregates (RCA) is considered beneficial to potentially substitute these aggregates in asphalt mixtures while concurrently providing secondary environmental, economic, and societal benefits. Nevertheless, engineering asphalt mixtures containing RCA to meet desired performance properties still poses several challenges and uncertainties for practitioners. Based on this, the present work reviews the previous relevant literature on this topic and summarizes the potential use of RCA for asphalt pavement related applications. An important characteristic of RCA is that it consists of various interfacial transition zones (ITZs) and voids caused by adhered mortar which leads to higher water-absorption and crushing characteristics as compared to NA. The treating methods used such as mechanical processing, calcium carbonate bio-deposition, and pozzolanic materials incorporation have been shown to be effective to improve the quality of RCA. The structural and material durability of RCA-asphalt pavement is closely dependent on its mix design, moisture-induced damage, and high and low temperature properties, which is in direct relation to the overall properties of RCA. Moreover, the shape variability of RCA during mixture preparation leads to the change in design gradation and its influence on the properties of RCA-asphalt mixtures should be carefully considered. The total substitution of coarse NA by RCA in asphalt pavement can be reached as long as the engineering properties, particularly the moisture susceptibility, are satisfactorily addressed. Overall, the potential application of RCA is a promising candidate to replace the excessive use of NA for the construction of high quality and sustainable asphalt pavements of the future.