Properties of Self-Compacting Concrete (SCC) Prepared with Binary and Ternary Blended Calcined Clay and Steel Slag

The recent emphasis on sustainable development in the construction industry has made it essential to develop construction and building materials that are not only affordable, but have minimal negative impact on the environment. This study investigates the valorisation of steel slag, which is mostly considered to be a waste material in several parts of the world, by blending with calcined impure kaolinitic clay to partially replace ordinary Portland cement (OPC) in the preparation of self-compacting concrete (SCC). OPC was substituted with steel slag at a constant level of 10%, whereas calcined clay replaced OPC at varying levels, ranging from 10 to 30% in a ternary blended mix. The hardened properties evaluated include compressive and flexural strengths. Samples containing only calcined clay showed a lower fluidity, which was significantly improved when steel slag was added to the mix. SCC containing 10% steel slag and 20% calcined clay obtained 28 days compressive strength, which was 3.6% higher than the reference cement concrete. An XRD analysis revealed a significant decrease in the peak heights of portlandite in mixtures containing steel slag and calcined clay, regardless of their replacement percentage. Generally, all the blended cement samples performed appreciably in resisting sulphate attack. The results of this study demonstrate that using steel slag and calcined clay together can significantly improve the fresh and hardened properties of SCC without compromising its mechanical properties.