In the current research work steel mill scales, waste from steel industries has been tested out as a fractional replacement for sand. Steel mill scale is a waste product obtained from the steel production industries and it has an adverse effect on the environment. Steel mill scale has become a good substitute for fine aggregates in the construction industry. The experimental parameter was the percentage of steel mill scale substitution (0%, 20%, 40%, 60%, 80% and 100%) by weight to fine aggregate content in M30 grade concrete and the results obtained from those mixes are compared with original M30 grade concrete. Compressive strength, split tensile strength, flexural strength and micro-structural characters of such concrete were evaluated. The interaction of steel mill scale within the concrete has been methodically investigated using micro-structural studies. It was found that very small particle size of steel mill scale fills the voids between the fine and coarse aggregate thus makes dense concrete. The test outcomes suggest that recycling steel mill scale by utilizing as a fractional replacement for fine aggregate offers a viable cost effective and environmentally friendly solution at 60% replacement.