Permeability, Compaction, and Corrosion Characteristics of Volumetrically Stable BOF Steel Slag-Fly Ash Mixture

Basic oxygen furnace steel slag (BOFSS) has been widely investigated for its use in both bound and unbound pavement layers. BOFSS particles entail both volumetrically unstable components and heavy metals. In this study, a volumetrically stable mixture that contains 80% BOFSS and 20% FFA by weight (BOFSS20FFA) was produced and tested. Basic characterization tests (i.e., specific gravity, sieve, and hydrometer) were performed on the BOFSS and BOFSS20FFA mixture. Compaction behavior and the permeability of the mixture were assessed. The corrosion potential of the mixture was evaluated through pH and electrical resistivity tests. The results of the leaching tests performed on BOFSS and FFA samples used in this research study were also evaluated. The dry unit weight of BOFSS20FFA was higher than that of BOFSS, corresponding to a lower optimum moisture content. The hydraulic conductivity of BOFSS20FFA was close to fine-grained soils due to the increased fines content and inter-particle cementation. pH measurements and electrical resistivity tests on the samples indicated the relatively high corrosion potential of BOFSS20FFA. The leachate analysis on BOFSS indicated that heavy metal concentrations in the leachate for almost all metal parameters tested (except chromium) were within the acceptable limits of generally accepted local and international drinking water standards. On the other hand, the results obtained for FFA were well above the limits of drinking water standards. These results showcase the importance of FFA selection in the geo-material mixture designs. As the heavy metal concentration depends on various site-dependent factors, pH-dependent advanced laboratory tests and field tests are required to better understand the environmental impacts of using mixtures.