Abstract: - The waste materials which can be used as additional cementitious material like fly ash, micro silica, blast furnace, metakaolin, steel slag etc. From all these waste material the most successful cementitious material is silica fume. To decrease the amount of cement in concrete supplementary material are used. For this investigation micro silica is replaced by 0%, 5%, 7.5%, 10%, 12.5%, 15% & 20% by the weight of cement. Water binder ratio is taken 0.45 for M-35 grade of concrete. From this reserach the results showed that compressive strength, bending strength, split tensile strength at 12.5 percent replacement of silica fume replaced with cement is optimum after that strength were decreased.

Keywords: Silica Fume, water cement ratio, compressive strength, flexural strength, tensile strength