Recent years have witnessed a transition in construction practices from using natural resources to recyclable materials. Utilizing recycled aggregate base (RAB) in the unbound pavement layers gives a viable and relevant strategy to the pavement industry, contributing to the greater goal of resource conservation. The first significant stage in this transition is to assess the strength of RABs and determine whether they are a viable alternative to natural or virgin aggregate (VA). Recycled concrete aggregate (RCA) and reclaimed asphalt concrete (RAP) are the two primary forms of RABs utilized in the construction of unbound layers of pavement. This research is focused on the stress state analysis of the RABs mentioned above, along with a control VA (limestone) using a nondestructive method (Falling weight deflectometer, FWD). It tries to identify a method of predicting if a granular layer is experiencing stress hardening and/or softening in the field. The analysis showed that fine RCA was the better material, followed by coarse RCA, RCA+RAP, and limestone.Further, borderline slope, a measure to assess stress state condition in the field, was obtained only in the case of limestone. In addition, this study also compared the results of laboratory-measured resilient modulus (MR) of all the materials with backcalculated layer modulus (EFWD). Pavement structures are modeled under layered elastic and finite element methods to obtain vertical strains at the mid-depth of each layer. Subsequently, the resulting vertical strains are compared to evaluate the difference in the two stiffness parameters. For all types of RABs, field vertical strains are lower than those based on the lab values. In the case of limestone, both strains are comparable, enabling a correlation between the MR and EFWD.
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