Abstract
Recycling materials have long been associated with environmental sustainability and circular economy growth. In recent years, the pavement industry’s efforts to use recyclable materials have started bearing fruits. Research studies on the replacement of natural aggregates or virgin aggregates (VAs) with recycled aggregate base (RAB) materials have not only shown favorable outcomes concerning environmental benefits but have also proven that the use of RAB materials can have a positive impact on the structural integrity of any pavement system. Nonetheless, it is generally agreed that further research is needed before the full-scale implementation of RAB materials. This article documents an effort to analyze the behavior of RAB and VA layers under varying stress states using a nondestructive method. The stress state of base materials in four test sections was evaluated using multiple falling weight deflectometer (FWD) load levels. Backcalculated FWD layer moduli of the materials were used in the National Cooperative Highway Research Program 1-37A model (American Association of State Highway and Transportation Officials 2004) to estimate nonlinear material parameters or stress dependencies. The analysis showed that fine recycled concrete aggregate (RCA) has a better performance, followed by coarse RCA, RCA+ reclaimed asphalt pavement (RAP), and limestone, respectively. The article also shows a quick method for predicting the condition of stress hardening or softening in materials in the field, based on FWD deflections.
