AbstractIn the process of making steel, around 10%–15% of slag is produced. In the last decade, several studies have proposed the application of steel slag as geomaterial. However, its potential application as a subgrade material in river embankments (artificial banks to protect the adjacent land against flooding) has been unexplored hitherto. This study assessed the geotechnical properties of steel slag, riverbank sand, and their various blends. First, the index properties, microstructure, and mineralogy of the slag and sand were evaluated. Then, the strength properties of slag and sand were assessed via the direct shear test at different relative densities and blends. The hydraulic conductivities of the proposed blends were also assessed, and the pH of their effluent discharge was evaluated. The optimal slag-sand mix for strength was found to be 1∶7 (slag content 12.5%), which improved the friction angle of sand from 27° to 37°. The hydraulic conductivities of all the proposed blends were observed to be in the range of 10−5 m/s, equivalent to that of riverbank sand. Hyperalkalinity of the leachate was observed during the hydraulic conductivity tests. The findings from the present study reveal that substituting a small proportion of riverbank sand with slag improves its strength considerably. However, there are geo-environmental concerns over its application in river embankments due to the hyperalkalinity of the effluent.