Optimization of fly ash concrete mix - A solution for sustainable development

This paper presents a method for optimizing fly ash concrete mix using the data obtained through planned experimental program. The full factorial experimental technique involving three factors with their four levels (4x4x4) were used. A total of 64 mixes with three replicates (192 specimens) were cast by taking three parameters for optimization. The three parameters were water to binder ratio (0.4, 0.45, 0.5, 0.55); coarse aggregate to total aggregate ratio (0.5, 0.55, 0.6, 0.65) and four percentages of fly ash i.e. 0%, 25%, 40% & 60%. The cement density used in the experimental program were 400 kg/m³. These parameters were taken in such a way that the various combinations of these factors would yield optimum concrete mix in the practical range of compressive strength. Two grades of concrete i.e. M20 and M30 were obtained from experimental investigation. The experimental data were utilized to develop the regression model for compressive strength in terms of three design factors considered in this study. The test results showed that optimum compressive strength was achieved at 0.45 water to binder ratio and 0.6 coarse aggregate to total aggregate ratio at 25% replacement of cement with fly ash.