ENVIRONMENTAL LEACHING ASSESSMENT OF EAF AND CASTER SLAGS FOR BENEFICIAL USE IN TRANSPORTATION INFRASTRUCTURE

Abstract

Steelmaking slags are increasingly considered sustainable alternatives to naturalaggregates; however, conventional engineering characterization and single-point leaching tests provide limited insight into their environmental performance under changing conditions. This study develops a structured framework to evaluate the engineering suitability and leaching behavior of Electric Arc Furnace and caster slags for road construction. Engineering characterization examined the physical, gradation, and compaction properties of the slags and shale soil mixtures, showing that slag type affects density, moisture requirements, particle structure, and potential field performance. Environmental screening combined the Toxicity Characteristic Leaching Procedure with pH-dependent batch extraction testing. Both slags met hazardous waste classification criteria, but batch testing showed pH- and particle-size- dependent constituent release, with several elements exceeding screening benchmarks under specific conditions. Continuous-flow column testing showed that slag-amended soil maintained alkaline buffering unlike unamended soil. Calcium release remained relatively stable, boron showed initial flushing followed by depletion, and vanadium increased during percolation, indicating potential long-term relevance. Outdoor lysimeter exposure demonstrated that leaching under natural weathering was environmentally sensitive rather than continuous, with precipitation, pH, and seasonal conditions affecting leachate chemistry. Manganese remained the primary regulatory concern, while calcium and magnesium exhibited contrasting behavior. Collectively, the findings show that beneficial reuse requires integrated consideration of engineering properties, pH-dependent leaching, percolation, and natural weathering. The framework supports reliable decisions regarding the environmental management and transportation use of steel slag.