Elastan-Polyurethane Treatment for the Stability Improvement of Coal-Fouled Ballast

Abstract

This study assesses the performance of coal-fouled ballast upon treatment with a hydrophobic elastomeric polyurethane, Elastan [Elastan-stabilized fouled ballast (ESFB)] and compares it with ballast that was initially clean but became fouled after its treatment during the track service life [fouled Elastan-stabilized ballast (FESB)]. The cyclic test results revealed that the performance of ESFB was significantly poorer compared with FESB for similar levels of fouling. The ESFB had undergone higher extent of deformations and had exhibited lower damping and resilient modulus values when compared with FESB. However, the extent of breakage of ballast particles was almost similar in both ESFB and FESB samples. Further, the extent of shear strains developed in ESFB samples, especially at higher void contamination index (VCI) values and loading frequencies, exceeded the shear strain at which breakage of bonds occurred under direct shear loading conditions. Accordingly, the critical loading frequency and fouling content up to which the polyurethane-based treatment is effective is proposed in the current study. In addition, the deformations of both stabilized and unstabilized ballast are seen to be directly influenced by the interface shear strength of ballast.