Characterization of Asphalt Binder and Mixture for Enhanced Railway Applications

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.

Keywords: crumb rubber modifier (CRM); indirect tensile strength (ITS); railway; rutting; styrenic thermoplastic elastomer (STE); tensile strength ratio (TSR).

Figure 6

(a) ITS test setting in a loading frame; (b) load–deformation curve after indirect tensile strength test.

Figure 1

Flow chart of experimental design procedures.

Figure 2

Aggregate gradation chart (ACT13WC).

Figure 3

Aggregate gradation chart (ACT20MC).

Figure 4

SGC equipment and compactor mechanism: specimen sample.

Figure 5

(a) Kim test setting in a loading frame; (b) load–vertical displacement (P-V) curve after deformation strength test.

Figure 7

Wheel tracking test equipment for roadway asphalt pavement. (a) Illustration of WT test equipment concept; (b) illustration of actual MWTT setup.

Figure 8

Dynamic stability curve obtained from the wheel tracking test.

Figure 9

Results for mechanical properties of asphalt mixtures for the asphalt concrete track.

Figure 10

TSR results for 13 mm and 19 mm asphalt mixtures.

Figure 11

Graph of final deformation for each asphalt mixture.

Figure 12

Rate of deformation by number of passes for each asphalt mixture.

Figure 13

Results of the dynamic stability for each asphalt mixture.