The document discusses a study on the effect of replacing cement with silica fume and river sand with manufactured sand (M-Sand) on the mechanical and durability properties of high strength concrete. Concrete mixes were prepared by replacing cement with 0%, 5%, 10%, and 15% silica fume and river sand with 100% M-Sand. Testing showed that the 10% silica fume replacement mix achieved the highest compressive strength, split tensile strength, and flexural strength. It also exhibited lower water absorption and moisture migration rates compared to the other mixes. The study concluded that partial replacement of cement with 10% silica fume and river sand with 100% M-Sand improves the mechanical and durability properties