An Experimental Investigation of Partial Replacement of Cement and Sand by Silica Fume and Stone Dust in Concrete

The development of concrete technology can decrease the use of natural resources and energy sources and lessen the burden of pollutants on environment. The major benefit of supplementary cementitious material is their ability to return certain amount of cement and still capable to present cementitious property, as a result reducing the cost of using Portland Pozzolana cement. The waste materials which can be used as additional cementitious material like fly ash, silica fume, blast furnace, stone dust etc. From all these waste material the most successful cementitious material is silica fume and stone dust because it improves the strength and durability of concrete to such level that recent design rules also identify for the addition of silica fume and stone dust for design of high strength concrete. Silica fume is also known as micro silica; it is used as an artificial pozzolanic super plasticizer. Stone dust is a waste material obtained from crusher plants. It has potential to be used as partial replacement of natural river sand in concrete. Use of stone dust in concrete not only improves the quality of concrete but also conserve the natural river sand for future generations. Substitution of normal sand by stone dust will serve both solid waste minimization and waste recovery. To reduce the amount of cement and sand in concrete supplementary material are used. Silica fume and stone dust are most popular material used in the concrete to improve its compressive, flexural, split tensile strength and also increase its durability. For this purpose silica fume is partially replaced by 0%, 5%, 7.5%, 10%, 12.5% and 15% by the weight of cement and stone dust is partially replaced by 0%, 10%, 15%, 20%, 25% and 30% by the weight of sand. The design mix proportion of 1:1.55:3.44 at water cement ratio of 0.50 were used for M20 grade of concrete. Various tests were conducted in the research which showed the results of the above percentage for the time period of 3, 7, 14 and 28 days curing as a substitution of cement by silica fume and sand by stone dust on compressive strength, flexural strength, split tensile strength and durability. The results show the maximum increase in strength of concrete occurred when cement and sand were replaced by 10% silica fume and 20% stone dust.