Mechanistic Evaluation of Geosynthetic-Reinforced Recycled Aggregates: Shear and Interfacial Performance for Sustainable Pavement Applications

Growing demand for natural aggregates (NA) in infrastructure development necessitates sustainable alternatives like recycled aggregates (RA) derived from construction and demolition waste. This study investigates the shear and interfacial shear behavior of geosynthetic reinforced natural aggregate wet mix macadam (NAWMM) and recycled aggregate wet mix macadam (RAWMM) through large-scale direct shear (LSDS) testing. To ensure accurate evaluation, the LSDS tests were conducted using a custom-fabricated apparatus measuring 500×500×300 mm (length × breadth × height). The tests included nine types of geosynthetic reinforcements made from polypropylene (NAPPGRD1-3) and polyester (NAPETGRD1-5, NAPETGTX) embedded in NAWMM and RAWMM at the interfaces. The results indicate that unstabilized NAWMM and RAWMM exhibits comparable shear behavior. The interfacial shear coefficients (α) for NAWMM ranges from 0.91 to 1.10 for PP-type reinforcements and 0.90 to 1.10 for PET-type reinforcements. In contrast, for RAWMM, the interfacial shear coefficients values vary between 0.82 and 0.99 for PP reinforcements and 0.78 to 0.99 for PET reinforcements. Among the geogrids, NAPPGRD1 and NAPETGRD1-5 have performed better in passive resistance. The interface shear modulus under normal stresses of 30, 45, and 60 kPa exhibits nearly identical behavior for NAWMM and RAWMM. Given the comparable shear and interfacial characteristics of these materials, RAWMM can be considered a suitable alternative to NAWMM. This study demonstrates the potential for replacing NAWMM with RAWMM, promoting sustainability and environmental responsibility. These findings provide critical insights for optimizing pavement design by improving material selection and reinforcing techniques, enhancing durability and sustainability.