The demand for natural sand as a construction material has increased significantly in recent years, leading to its depletion and environmental concerns. This research paper investigates the use of quarry dust and fly ash as partial replacements of sand in concrete. The study aims to determine the effect of varying proportions of quarry dust and fly ash on the mechanical and durability properties of concrete. Experimental investigations were conducted on concrete mixes with replacement levels of 0%, 10%, 20%, and 30% of sand with quarry dust and fly ash. Compressive strength, split tensile strength, and flexural strength were tested at 7, 14, and 28 days. Durability properties such as water absorption and permeability were also studied. The results showed that the addition of quarry dust and fly ash had a significant effect on the compressive, split tensile, and flexural strengths of the concrete. The compressive strength of concrete increased with the increase in quarry dust and fly ash content up to 20% and then decreased at 30% replacement. Similarly, split tensile and flexural strengths showed a similar trend. The water absorption and permeability of the concrete decreased with the increase in quarry dust and fly ash content.