Railroad ballast fouling and degradation can reduce track support conditions, increase maintenance requirements, and negatively affect long-term track performance. Asphalt underlayment has been successfully used beneath ballast layers to improve structural support, reduce the migration of fine particles, extend maintenance intervals, and potentially improve safety of railroad tracks. However, the relatively high cost of asphalt materials has limited wider implementation of this technology across the rail industry. This project investigates the feasibility of incorporating recycled asphalt pavement (RAP) and ground tire rubber (GTR) into asphalt underlayment mixtures for railroad applications. The proposed approach seeks to improve the cost-effectiveness of railroad track infrastructure while maintaining adequate mechanical
performance. RAP can reduce the demand for virgin aggregates and asphalt binder, while GTR provides an opportunity to beneficially reuse end-of-life tire materials and potentially enhance mixture durability. The project consists of three integrated components. First, a comprehensive literature review will summarize current knowledge and practice regarding asphalt underlayment applications in railroads, recycled asphalt materials, and rubber-modified asphalt technologies. Second, laboratory mix design and performance testing will be conducted to evaluate asphalt underlayment mixtures containing varying RAP and GTR contents. Dynamic modulus and flow
number tests will be used to characterize stiffness and deformation, which are critical performance indicators for railroad underlayment materials. Finally, a life-cycle cost assessment (LCCA) will be performed to quantify the economic benefits of incorporating recycled materials relative to conventional asphalt underlayment mixtures. The expected outcome is the identification of practical mix designs that balance performance, cost, and other potential benefits. The project will provide guidance for the use of recycled materials in railroad asphalt underlayment applications and establish a foundation for future field implementation and performance evaluation.