Comparative Study Using Wash Bottom Ash and Steel Slag by Replacement by Fine Aggregate

The escalating global demand for natural aggregates and the environmental challenges associated with industrial waste disposal have driven the construction industry toward more sustainable practices. This review paper synthesizes current research on the integration of industrial by-products—specifically steel slag (SS), coal bottom ash (CBA), and waste foundry sand (WFS)—as partial or full replacements for fine aggregates in various concrete types, including Ordinary Portland Cement (OPC) , geopolymer , and ultra-highperformance concrete (UHPC).A critical analysis of the literature reveals that the mechanical performance of concrete containing these substitutes is generally comparable or even superior to conventional concrete at optimal replacement levels. For instance, studies indicate that a 30% replacement of sand with a combination of bottom ash and waste foundry sand can yield mechanical properties (compressive, flexural, and splitting tensile strength) equivalent to or exceeding control mixes. Similarly, the optimal replacement level for steel slag is typically reported between 30% and 60%, enhancing both strength and durability characteristics. In specialized applications, such as foamed concrete, crushed steel slag has proven feasible for both structural and non-structural purposes. Despite these benefits, the review identifies challenges such as increased water demand to maintain workability and the necessity for specific processing, such as washing bottom ash to reduce carbon content. The paper concludes that while industrial by-products offer a sustainable alternative to river sand, further research is required to standardize their use across diverse environmental conditions and specialized concrete applications.