Avaliação da resistividade elétrica e liberação de finos da escória de aciaria como lastro ferroviário

Abstract

The steel industry plays a fundamental role in the global economy; however, its operation results in the significant generation of waste. At the same time, railway transportation stands out for its high freight efficiency, although it requires substantial consumption of natural resources for its infrastructure. In this context, a sustainable strategy is the reuse of steelmaking waste as aggregate for railway ballast. Therefore, this study aims to evaluate the technical feasibility of using treated steel slag as railway ballast aggregate (steel slag ballast), with particular emphasis on fines generation and electrical resistivity, the latter still scarcely explored in the literature. To this end, tests of apparent specific gravity, apparent porosity, water absorption, Treton impact toughness index, Los Angeles abrasion, electrical resistivity under different moisture and fines contents, expansion assessment using the adapted PTM method, and the correlation between fines content and abrasion cycles were conducted. The results indicated an apparent specific gravity of 3,122 kg/m³, water absorption of 2.0%, and apparent porosity of 5.5% (above normative limits). The Treton toughness index obtained for the slag was 9.6%, and the Los Angeles abrasion value was 20.3%, both in accordance with the literature and superior to natural aggregate (gneiss), which presented 21.8% (Treton) and 21.6% (Los Angeles abrasion), indicating better mechanical performance of the slag. Regarding electrical resistivity, slag exhibited adequate values under dry conditions (2,580,000 Ω·m, compared to 3,900,000 Ω·m for natural aggregate). However, with increasing moisture, resistivity decreased, reaching values close to or below 60 Ω·m, while natural aggregate maintained 528 Ω·m at 16% moisture. The addition of fines and iron ore contamination was also detrimental, with slag reaching as low as 27.9 Ω·m. Therefore, steel slag ballast is not recommended for railway tracks operating with track circuit detection systems, but it is suitable for sections that employ axle counter detection systems. These findings support the feasibility of using steel slag as ballast, with restrictions in systems that rely on electrical track circuits.