DEVELOPMENT OF VARIOUS CHARACTERISTICS AND FRACTURE MECHANISM OF HIGH STRENGTH CONCRETE AT OPTIMUM CONTENT OF SUPPLEMENTARY CEMENTING MATERIALS AND STEEL FIBERS

摘要

The high strength concrete has been found brittle in nature due to smooth failure plane between the closely packed dense matrix of aggregates and cement paste; results in sudden failure of the structure. Investigation through the literature data provides considerable variation in the mechanical properties of it, containing part replacement of cement with supplementary cementing materials (SCM) and various proportions of steel fibers. More research and results are required to evaluate the function of SCM and steel fibers for the development of different characteristic of high strength concrete. The present paper contributes a part of current investigations made through experimental laboratory work to evaluate the mechanical and shear properties of high strength steel fiber reinforced concrete (SFRC). Parametric variations of silica fume from 5 to 15% and fly ash 30% have been used as replacement of cement to ascertain the properties of concrete. The quantity of steel fibers varies from 0.5 to 2% with 0.5% increment was used in the experimental study. Besides for comparison, one mix named controlled mix was produced without silica fume contents and steel fibers. The prime objective includes determining the optimum SCM content by progression of laboratory experiments for the most favorable mix proportions of high strength SFRC. An average slump loss for all the three mixes has been found as 78% from 0 to 2% steel fiber volume corresponding to 12% silica fume, 1.5% steel fiber volume and 30% fly ash. The strength ratio development from 7 to 56 days of high strength SFRC has been found as 0.85 whereas the same was found as 0.65 corresponding to control concrete. This is perhaps due to the reason that silica fume improves the performance of high strength SFRC at early age and the pozzolanic material present in the fly ash react with residual lime and improve the characteristics of high strength concrete at later stage. The addition of silica fume with fly ash was found to increase the compressive strength of concrete at early age when compared to concrete made with fly ash alone.