Potential use of reclaimed asphalt pavement and recycled concrete aggregate in base/subbase layers of flexible pavements

In current road and pavement engineering practices, the lack of fresh natural aggregate (granular material) supplies with increasing processing costs have led to use various reclaimed/recycled materials from old structures as a source of construction materials. Reclaimed Asphalt Pavement (RAP), and Recycled Concrete Aggregate (RCA) have been used as aggregates for pavement construction for some time. This study is focused on the characterization of blended materials containing 50% and 75% of RAP with fresh granular materials and RCA to evaluate whether they are suitable for granular base/subbase layers of flexible pavements. A series of laboratory tests was performed to determine the resilient modulus (MR) and the constrained modulus (Mc) for both fresh granular materials and their blends. Statistically, the notable increase was found in the MR values of the blended samples containing 75% RAP material and 25% fresh granular, particularly at higher levels of bulk stresses. It was also found that the accumulative strains during cyclic loading generally increase with an increase in the percentage of RAP contents in the blended samples. Mc test results show an increasing trend with the increasing level of axial stress, however, Mc value decreases with increasing percentage of the RAP content. Never-the-less, the t-test showed that accumulative strains during Mc tests were found to increase significantly with an increase in the percentage of RAP contents.