Sustainable Application of Copper Slag as Fine Aggregate in High-Strength Concrete

The growing consumption of natural river sand in concrete manufacturing has led to serious environmental degradation and material scarcity, emphasizing the need for sustainable substitute materials. Copper slag, a by-product generated during the copper smelting process, has emerged as a potential alternative to fine aggregate in high-strength concrete. This investigation examines the behavior of M60 grade concrete in which copper slag replaces natural sand at proportions of 0%, 20%, 40%, 60%, 80%, and 100%. The fresh concrete properties were assessed using slump cone tests, whereas the hardened properties were evaluated through compressive strength tests conducted at 7, 14, and 28 days, along with split tensile and flexural strength tests performed at 28 days. The experimental results revealed an increase in workability with rising copper slag content, attributed to its smooth surface characteristics and minimal water absorption capacity. The highest compressive strength was recorded at a 40% replacement level, showing noticeable improvement over the conventional mix. However, replacement levels exceeding 60% resulted in a reduction in strength due to increased free water content and weaker interfacial bonding between the paste and aggregates. Similar performance patterns were observed for split tensile and flexural strengths, with optimal results obtained within the 40–60% replacement range. The study concludes that copper slag can effectively substitute up to 60% of natural sand in M60 grade concrete without adversely affecting structural performance, thereby supporting sustainable construction and efficient utilization of industrial waste.