Influence of water/powder ratio on strength properties of self-compacting concrete containing coal fly ash and bottom ash

The paper deals influence of water/powder ratio on strength properties of self-compacting concrete (SCC) containing coal bottom ash. SCC was made with coal bottom ash as replacement of fine aggregates in varying percentages of 0%, 10%, 20% and 30% and fly ash as replacement of cement in varying percentages of 15–35%. Strength properties tests were carried out at the ages of 28, 90 and 365 days for the various mixes. s indicate the behaviour similar to normal SCC of increase in strength on decrease of water–powder ratio. A comparison between SCC with various fly ash contents and with various replacements of fine aggregates with bottom ash showed that SCC obtained strength increase on decrease of w/p from 0.439 to 0.414 for 0% bottom ash, 0.50–0.47 for 10% bottom ash, 0.58–0.51 for 20% bottom ash and 0.620–0.546 for 30% bottom ash. All mixes showed strength gain beyond 28 days and the mixes with 15% and 35% fly ash mixes gained strength of the order of 60 MPa and 40 MPa, respectively at 90 days. However, it was possible to produce SCC with a compressive strength of 40–50 MPa with 15–35% fly ash replacement. The bottom ash could be used up to 20% keeping in view the decrease of strength of about 15–20% (if fly ash percentages with 15% and 20% are not taken into consideration), as they show higher decrease of strength. Thus, the optimum fly ash percentage was 25–35% and bottom ash percentage was up to 20% in the present study.