INVESTIGATION OF STRUCTURAL PROPERTIES OF HSC WITH SILICA FUME AND FLYASH

Abstract

High — strength concrete (HSC) has many advantages, running from economical to structural. HSC structural elements can be produced with smaller cross section, they cost less in materials and occupy less space. In terms of engineering characteristics, HSC yields a higher modulus, less creep and shrinkage. Due to these advantages, the interest in HSC has reached global proportions. The present study aims at producing concrete with high — strength using locally available materials. The dissertation is also an experimental investigation of the effect of silica fume and fly ash on the various properties of HSC viz. compressive strength, split tensile strength, unit weight, modulus of elasticity, drying shrinkage, moisture movement and coefficient of thermal expansion: For this purpose, three types of mixes were prepared with different material compositions. One mix was prepared without adding any pozzolanic material. In the second mix, p,art of cement by weight :vas laced 1:,,y the fl:y. ash arid silica f.unic and 'clic third mix was prepared by the partial replacement of cement by silica fume alone. Superplasticizer was used in all the mixes. Cubes, cylinders and prisms of different mixes were cast to investigate the various properties of HSC. Silica fume, being a highly reactive pozzolan, effects mainly the early age characteristics of HSC while fly ash is effective mainly at later ages. A combination of silica fume and fly ash was found to be effective in achieving high — strength of concrete at all ages. Along with the cube strength, the 28 days tensile strength of concrete was also increased. The modulus of elasticity of high — strength concrete as calculated from the stress — strain curves, was high. The HSC mixes showed low shrinkage and moisture movement. The silica fume and fly ash were observed to reduce the shrinkage and moisture movement. The coefficient of thermal expansion of all the three mixes were nearly the same. iii The relevant review and the experimental results etc. are covered in detail in the thesis. This study has helped the author gain considerable insight into the procedure of mix design for HSC and also an understanding of its main structural properties. The author hopes that the results and conclusions will also be useful to others. iv