Exploring the Stabilization Potential of Electric Arc Furnace Slag in Silty Soils through Multifaceted Micro- and Mesoscale Characterization

Soil stabilization using chemical additives is a proven technique for enhancing the strength and performance of weak subgrade soils. Electric arc furnace (EAF) slag has shown significant potential to improve the geotechnical and mechanical properties of soils because of its unique chemical and physical characteristics. However, the heterogeneous nature of EAF slag makes it challenging to determine whether a specific source is suitable for stabilization purposes. This study aimed to identify key EAF micro- and mesoscale properties that contribute to the development of effective soil stabilization mechanisms. To achieve this, a comprehensive characterization program was established to evaluate the slag’s chemical, physical, mechanical, morphological, and mineralogical characteristics. Fully graded EAF samples and slag fines were considered for soil stabilization. A silty clay soil considered poor for pavement applications according to the AASHTO classification system was stabilized with different additives (fly ash, cement, and EAF) to assess the effectiveness of the steel coproduct as a stabilizing agent. Chemical analyses confirmed the presence of key oxides (CaO, SiO₂, and Al₂O₃) in the EAF samples, although limited reactivity was observed because of dominant crystalline phases. In the soil mixtures, the swelling potential was reduced from 0.92% to 0.29%, and strength significantly improved with slag fines, indicating pozzolanic activity. When combined with 2.5% cement, EAF slag produced synergistic effects, outperforming cement alone with an increase of 17% for 7 days of curing. The findings highlight the importance of slag composition and confirm its viability as a sustainable, performance-enhancing alternative for soil stabilization.