ENHANCING CONCRETE PROPERTIES BY ADDING SILICA FUMES : Compressive Strength

Abstract

Due to over increasing population and limited resources of land we have to look to the sky to accommodate this increasing population and for that we are so much focused on making high rise buildings and other mega structures to utilise the resources of land to its fullest, but this cannot be achieved without improving our construction technique and materials. As we know that Concrete is one of the most widely used structural material hence its property and quality influence the construction a lot. Here in my project I have tried to evaluate those properties of concrete and the improvement in those properties by adding silica fume. Silica fume act as a filler material and fills the pores between cement particles, making it more dense and improving the microstructure of concrete and thus improving the mechanical properties of concrete, such as strength, impermeability, durability, elastic modulus and so on. It also improve the concrete by chemically reacting with hydration precipitation of Ca(OH2) and producing hydrated calcium silicate in alkaline conditions thus improving the consistency of concrete and workability. Compressive strength of concrete is the most important property of concrete, because other properties like stress-strain relationship, tensile strength, bond strength, modulus of elasticity, density, impermeability, durability etc. can be inferred from the compressive strength using established correlations. Therefore in this project I have focused on observing the improvement in compressive strength of concrete by adding silica fumes and finding the most optimum proportion of silica fume which gives us the best result. Different mix design are prepared following IS code and different proportion of silica fume (i.e. 0%, 5%, 10%, 15%, 20%) are added and the results of 7 and 28 days compressive strength are found and compared. The result shows a progressive increase in compressive strength of concrete (corresponding to 28 days strength) till 15% of silica fume and then it slightly decreases hence we can correlate that the most optimum proportion of silica fume that should be added in concrete is about 15% of total cementitious material. Adding silica fume also improves the early strength of concrete (i.e. 7days strength), durability etc as discussed in the project.