Mechanical Properties of Concrete Composites with Replacement of Class C Fly Ash and Silicafume

The results of experimental investigations on the study of concrete with partial replacement of cement are presented in this paper. The concrete grade of M30 has been selected and designed as per Indian Standard method. The specimens based on control mix have been cast without fly ash and silica fume. Cement was replaced by 0%, 10%, 20%, 30%, 40%, 50% and 60% of fly ash by the weight. 20 % of silica fume was added to all those mixes and further replacement of cement was tried. Necessary tests were carried out in fresh and hardened concrete. Workability was found from slump test. Tests for compressive strength were carried out on specimens at the age of 1, 7, 14, 28, 56 and 90 days. The split tensile strength and bond strength tests were also carried out at the age of 28 days. The test results were compared with the results of specimen prepared after control mix. The results showed that the strength development of fly ash concrete was less in early ages and increased at higher ages when compared with control specimens. From this study it was concluded that 50% replacement of cement by fly ash contribute reasonable strength along with 20% of silica fume.