To develop self-compacting concrete of grade M25, M30 and M35 using composite cement

Both fly ash and slag are industrial by-products and their disposal has become a serious environmental problem. Considering their excellent cementitious properties, their utilization in the cement industry becomes crucial. Because of the significant contribution to the environmental pollution, over dependency on cement has to be reduced. There is a need to economize the use of cement, thus, the concept of composite cement becomes necessary. In this study, Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBFS) were used as partial replacement of cement to improve the properties of self-compacting concrete (SCC). Three SCC grades viz., M25, M30 and M35 were made in the laboratory. For all the three grades, two variations were considered. Case 1 included 65% Ordinary Portland Cement (OPC), 15% FA and 20% GGBFS while case 2 included 85% OPC and 15% FA. In order to improve the workability of SCC, certain amount of super-plasticizer was added in the design mix. V-funnel, L-box and slump flow tests were conducted on fresh SCC whereas compressive strength, flexural strength and split tensile tests were performed on hardened SCC. The results showed that the optimum admixture content was used their respective grades and cases leading to negligible segregation. Moreover, all the design mixes satisfied the SCC workability conditions comfortably. It was concluded that by replacing cement partially with fly ash and GGBFS in percentages mentioned in cases 1 and 2, the tensile strength of SCC could improve. From the 28 days results obtained from the compressive strength test, it was inferred that 15% fly ash and 20% GGBFS could be partially replaced with cement for all the grades i.e., M25, M30 and M35. This, could help in reducing the reliance on cement, and utilizing the industrial by-products in a better way.