Abstract
The upsurge in urbanization steered a substantial proliferation in the demand for concrete in the construction industry. As a result, there is a higher demand for cement and fine aggregate, as constituents of concrete. The detrimental effect of cement generation on the environment has been witnessed over the last 4–5 decades. Similarly, the increased demand for fine aggregate has led to extensive extraction of river sand, which results in negative impacts on the environment. Utilizing industrial waste materials like copper slag (CS) and mineral admixtures such as metakaolin (MK) in eco-friendly concrete production can help reduce this environmental impact. The primary objective of this research is to examine the impact on the mechanical and durability properties of concrete when using CS as a partial replacement for sand, combined with MK as a partial replacement for cement. To evaluate the mechanical characteristics of concrete, tests were conducted to measure split tensile strength, compressive strength, and flexural strength, and its durability was assessed via a rapid chloride ion penetration test. The microstructural analysis of concrete was also performed using scanning electron microscopy and energy dispersive spectroscopy. The optimum percentages of the MK and CS were as fractional switches of cement and sand, respectively, were assessed using the response surface methodology (RSM). The optimal strengths were found at 15% MK and 31.533% CS, while experimentally, the best performance of modified concrete was obtained at 30% CS. The experimental findings and predicted values from the RSM model showed a strong correlation with R-squared (R 2) values obtained as 0.9880 and 0.9552 for compressive and flexural strengths, respectively. The findings have significant implications, as they provide a sustainable alternative to sand while enhancing the performance and longevity of concrete structures.