# Characterization of Asphalt Binder and Mixture for Enhanced Railway Applications

## TL;DR

This study evaluates asphalt mixtures for railway use, showing that modified binders improve strength and durability under dynamic and temperature-related stresses.

## Contribution

The paper introduces insights into asphalt binder performance for railways, emphasizing modified mixtures' enhanced tensile and freeze-thaw resistance.

## Key findings

- Higher PG grades and modified binders increase indirect tensile strength in asphalt mixtures for railroad layers.
- Modified mixtures with CRM and STE show over 92% tensile strength ratio, improving freeze-thaw durability.
- Modified asphalt mixtures exhibit twice the rutting resistance compared to unmodified ones, reducing permanent deformation.

## Abstract

Although asphalt mixtures can be applied to railway tracks due to their viscoelastic properties, caution is required, as their ductility and brittleness are highly sensitive to temperature variations. In recent years, interest in the application of asphalt in railway infrastructure has increased, driven by the development of modified mixtures and the broader availability of performance-enhancing additives. Additionally, evaluation methods for railway tracks should be adapted to account for the distinct loading mechanisms involved, which differ from those of conventional roadways. In this study, the comprehensive properties of asphalt binders, mixtures, and testing methods—including physical and engineering characteristics—were assessed to improve the performance of asphalt concrete layers for potential applications in railroad infrastructure. The results of this study indicate that (1) the higher the performance grade (PG), the higher the indirect tensile strength (ITS) value achieved by the 13 mm mixture using PG76-22, which is higher than that of the PG64-22 mixture. This indicates that higher PG grades and modification contribute to improved tensile strength, beneficial for upper layers subjected to dynamic railroad loads. (2) The tensile strength ratio (TSR) increased from the unmodified mixture to over 92% in mixtures containing crumb rubber modifier (CRM) and styrenic thermoplastic elastomer (STE), demonstrating enhanced durability under freeze–thaw conditions. (3) Wheel tracking test results showed that modified mixtures exhibited more than twice the rutting resistance compared to PG64-22. The 13 mm aggregate mixtures also generally performed better than the 19 mm mixtures, indicating reduced permanent deformation under repeated loading. (4) It was concluded that asphalt is a suitable material for railroads, as its overall characteristics comply with standard specifications.