Durability of steel slag as railway ballast under freezing–thawing and salt crystallization weathering

Abstract

This study aimed to assess the suitability of steel slag (SS) as railway ballast in Yazd province, Iran. Quantitative tests and comparisons with international standards evaluated SS’s effectiveness against freezing–thawing (F–T) and salt crystallization (S-C) weathering. The findings revealed that SS was rich in CaO, Fe₂O₃, SiO₂, MgO, and Al₂O₃, which contributed to alkalinity, stability, and durability. However, increasing weathering cycles significantly impacted density, with a 42% decrease after 35 S-C cycles and a 12% loss after 45 F–T cycles. Los Angeles abrasion tests revealed increased abrasion with higher F–T cycles, attributed to ice crystallization in pores. Similarly, magnesium sulfate cycles elevated abrasion from 6.18 to 17.3%, impacting performance though remaining within permissible limits. Weathering also significantly compromised SS strength, with the point load index dropping from 8.4 to 2.4 MPa after 45 F–T cycles and 1.86 MPa after 35 S-C cycles, potentially impacting track stability and safety. Notably, salt crystallization presented a greater threat, potentially leading to fine formation and drainage problems. In conclusion, although SS initially appears to meet certain ballast requirements, its long-term vulnerability to weathering conditions raises significant concerns regarding its suitability for critical railway applications in environments with a climate prone to weathering.