Performance Evaluation of Virgin and Recycled Aggregate Blends for Unpaved Roads under Freeze-Thaw Cycles

Unpaved roads are vital for rural transportation across the United States, especially in agricultural regions like Iowa, where they make up about 74% of the roadway network. While they are cost-effective, these roads tend to deteriorate quickly due to traffic loads, environmental factors, and particularly freeze-thaw (FT) cycles. FT cycles cause expansion when freezing and create voids during thawing, weakening the road structure and reducing its load-bearing capacity. This study examines the impact of FT cycles on unpaved roads, utilizing both virgin quarry aggregates and recycled roadway materials. Six aggregate blends, three virgin and three recycled, were tested for index properties, resilient modulus (MR), and permanent deformation (PD). Results showed that recycled blends were denser and had higher stiffness but exhibited poorer resistance to PD than virgin aggregate blends. When subjected to two FT cycles, the MR of both recycled and virgin aggregate blends decreased. The PD results for the thawed materials after two and five FT cycles showed that virgin aggregates failed, whereas recycled blends stabilized after some initial deformation. These results indicate that using virgin quarry aggregate alone may lead to premature failure, particularly in regions with harsh winters, consequently increasing maintenance costs. Furthermore, balanced gradation plays a crucial role, with sand and fines contents contributing to the long-term performance of roadways.