This document presents the results of an experimental study on the strength properties of concrete with the addition of nanosilica. Cubes of M20 and M30 grade concrete were produced with 0%, 0.5%, 1%, 1.5%, 2%, and 2.5% partial replacement of cement with nanosilica. The cubes were tested for compressive strength and workability after 7 and 28 days of curing. For both grades, compressive strength initially decreased with 0.5% nanosilica but then increased up to 2% replacement, above which it decreased again. The 2% replacement provided the highest 7 and 28-day compressive strengths, increasing up to 15.9% and 18.7