Cyclic Behaviour of Black Cotton Soil Stabilized with a Ternary Blend of Ordinary Portland cement, Copper Slag, and Phosphogypsum

Abstract

Black cotton soils are notoriously difficult to work with in road construction. Because they swell easily and lose strength under the weight of traffic, they often
lead to pavement failure. In this study, we explored a more resilient solution: stabilizing the soil with a three-part blend of Ordinary Portland Cement (OPC),
Copper Slag (CS), and Phosphogypsum (PG). By putting these mixtures through a series of 'stress tests' that simulate repeated traffic loading, we found that the
ternary blend significantly stiffens the soil. While untreated soil tends to degrade quickly under pressure, our stabilized specimens held their ground much better.
This durability comes down to the cementation products such as calcium silicate hydrate and ettringite that forms during the curing process. Ultimately, this mix
not only met the strict stiffness standards required for modern road design but also offers a more sustainable way to build on challenging terrain. In addition, the
stabilized soil showed improved resistance to deformation and maintained its strength even after repeated loading cycles. The combined action of OPC, CS, and
PG created a denser soil structure, reducing the harmful effects of swelling and shrinkage. These findings highlight the potential of industrial by-products in
developing cost-effective and environmentally friendly pavement subgrade stabilization techniques.