Abstract The objective of this study was to evaluate the suitability steel slag as an additive engineering properties weak clay soil. Different geotechnical laboratory tests were conducted on both stabilized and natural soils. Steel (SS) added at a rate 0, 5, 10, 15, 20, 25% Specific gravity, grain size analysis, Atterberg limit test, compaction free swell, California bearing ratio (CBR), uncon...