Laboratory Investigation of Black Cotton Soil—Fly Ash—Steel Slag Mixes

Black cotton soil is one of the major soil deposits in India. They exhibit high swelling and shrinking when exposed to changes in moisture content and hence has found to be most troublesome from engineering considerations. In this study, geotechnical characteristics of black cotton soil with the addition of fly ash (FA) and steel slag (SS) mixes were investigated. FA and SS were added in the varying percentage of 5, 10, 15, and 20% of the weight of black cotton soil. Atterberg’s limit tests illustrated that 5–20% addition of FA and SS in the black cotton soil considerably reduces the volume change potential of the black cotton soil. Addition of FA and SS in black cotton soil also helps in reducing its swelling and shrinkage potential. The strength gain of the mixes not only depends on fly ash and steel slag content but also on mix gradation. The angle of internal friction for all mixes and the cohesion part of the shear strength was higher than that of the black cotton soil owing to strong bonding between steel slag and fly ash particles. Apart from the experimental results, the use of fly ash and steel slag has proven to be an eco-friendly material thereby reducing the dumping and disposal problems associated with fly ash and steel slag.