Concrete today as one of the most used and most popular building materials has a special place in construction. most countries will face a shortage of natural resources for the production of natural aggregates in the near future with increasing use of concrete, and there is no alternative to replacing new materials or reusing previous materials. In this study, with replacement of 25, 50, 75 and 100 percent, recycled sand instead of natural sand will be made. On the other hand, concrete mixes containing both natural and recycled aggregate are produced by replacing a fraction of Portland cement 1.5%, 3% ، 4.5% and 6% of colloidal Nano-Silica. Concrete compressive strength at the age of 3, 7, 28 and 56 days, and tensile strength, modulus of elasticity at 28 days of age were investigated. The use of recycled sand reduces the compressive strength, tensile and of concrete with recycled fine aggregate compared to the control concrete. This is due to the reduced resistance of the mortar in the sand. which adds colloidal nanosilica improve the mechanical properties of concrete