Effects of Cement Replacement with GGBF Slag on Sleeper Concrete Durability in Desert Areas: An Experimental Investigation

Approximately 600 km of Iran’s railway network traverse desert regions, where sand dune movement poses significant challenges to infrastructure integrity. One critical issue is the accumulation of sand on concrete sleepers, leading to longitudinal cracking caused by tendon corrosion due to chloride ion penetration. This degradation ultimately results in sleeper failure and drives repeated maintenance—an outcome with both economic and environmental costs. Ground-granulated blast furnace slag (GGBFS) is known to bind chloride ions while simultaneously reducing clinker demand; however, its application as a protective measure in desert sleepers remains underexplored. This study investigates the partial replacement of cement with GGBFS at 0%, 20%, 30%, and 40%—produced under real curing conditions without alkaline activators or chemical admixtures. Compressive strength tests revealed optimal replacement levels of 20% at 1 day, 30% at 7 days, and 40% at 28 days. Rapid chloride migration tests showed chloride penetration reductions of 52.5%, 69.4%, and 86.4% for 20%, 30%, and 40% GGBFS, respectively. Ultrasonic pulse velocity and electrical resistance measurements confirmed increased material density and refined pore structure, while SEM imaging illustrated microstructural densification in slag-rich mixes. By achieving up to 40% clinker substitution, this approach offers substantial embodied-CO₂ savings and valorizes an industrial by-product, aligning with circular-economy principles. The enhanced durability and extended service life of GGBFS-modified sleepers promise lower lifecycle emissions and reduced maintenance interventions—making this a compelling, low-carbon solution for sustainable rail infrastructure in arid, chloride-rich environments.