Studies on effect of maximum size of aggregate in higher grade concrete with high volume fly ash

In the present paper, an investigation is made to study the effect of maximum size of aggregate in higher grade concrete using high volume fly ash. Three different mixes of M50 grade concrete were designed using graded coarse aggregate of three maximum sizes of 10mm, 12.5mm and 20mm. And for each mix, cement was replaced with fly ash at 0%, 10%, 20%, 30%, 40% and 50% (%replacements). All the mixes were cured for 56 days and tested for compressive strength, flexural strength and splitting tensile strength. The test results obtained have suggested that the maximum size of coarse aggregate in M50 grade concrete at various replacement levels of fly ash was 12.5mm aggregate and optimum replacement of fly ash was 30%. The percentage increase was 20% for compressive strength, 20% for splitting tensile strength and 5% for flexural strength when compared to the design strength.