Effective Utilization of Fly Ash and Steel Slag for Partial Replacement of Cement and River Sand for Sustainable Construction

Abstract

There is always a rising demand for cement and natural resources for large-scale construction activities. Cement manufacturing unit is the major source of greenhouse gas emitter in the building sector. Industrial waste can be used in replacing a portion of cement and sand in concrete, without affecting the end quality of the concrete, yet creating a more sustainable ecosystem. The current study focuses on experimental study on partial replacement of cement with fly ash and river sand with steel slag as binder and fine aggregate, respectively. Preliminary investigations on the physical and chemical properties of steel slag and fly ash are carried out using X-ray powder diffraction (XRD) analysis as per the specification of Bureau of India Standards (BIS). The study further focuses on the characteristics of concrete in fresh and hardened state. Experiments are conducted on M20 grade concrete by varying the mix proportion of fly ash and steel slag to achieve the desired 7, 14 and 28 days compressive strength in accordance with BIS. It is observed that a 10 and 20% replacement of cement (by weight) with fly ash attains a 28 day compressive strength of 21.32 and 22.08 MPa, respectively. However, when partial replacement of cement with fly ash increased to 30%, the 28 day compressive strength dropped down to 14.01 MPa. This study also investigates the suitable proportion of steel slag as fine aggregate. Concrete blocks are made and their compressive strengths for different steel slag proportions, while maintaining the optimum percentage of fly ash as 20%. It is observed that, on replacing 10% of river sand with steel slag, a 7% rise in compressive strength is achieved when compared to the mix without steel slag. This study concludes that the maximum 28 day compressive strength of concrete achieved is 23.8 MPa by utilizing 20% of fly ash and 10% of steel slag as partial replacements for cement and river sand, respectively. This result reveals that industrial by-products could be effectively employed in manufacturing concrete blocks for sustainable construction by minimizing the use of natural resources.