Steel Slag (SS) is an industrial by product get from the steel manufacturing industries .It is produced in large quantities during the steel making operation which utilize electric arc furnaces .SS can also be produced by smelting iron ore in the basic oxygen furnace. SS can be used in construction industry as an aggregate in concrete by replacing natural aggregate. Natural aggregate are becoming increasingly scare and their production shipment is more difficult. SS is used for aggregate in hot as plat surface application. The majority of the aggregate is quantity of the concrete. Replacing all or a few of the natural aggregate with the SS will leads to some environmental benefits. For this present study M25 concrete is used. The one-sided substitute of the SS will be made for changing percentages, for example 0%,10%, 20%,30%,40%,50%. From this learn the compressive strength, flexural strength and split tensile strength will be made experimentally also to find the optimal level of SS at a particular replacement of SS as natural aggregate.