STRENGTH CHARACTERISTICS OF FLY ASH CONCRETE WITH SAME WORKABILITY

For making high strength concrete, cement can be replaced by fly ash (collected from Vijayawada Thermal Power Station) upto an extent of 50% without affecting either compressive strength or flexural strength.It is proposed to investigate the effect on strength of fly ash concrete when water-binder ratio changes with same workability as that of basic mix.The consistency of cement decreases with increase in fly ash percentage.But no definite pattern is noticed in respect of initial and final setting times, through in all cases.The water-binder ratio, for a compaction factor of 0.72, reduces from 0.370 for basic mix to 0.335 for mix with 50% replacement of fly ash.The average increment in compressive strength at 28 and 90 days is 7% and 2% respectively.However, the average increment in flexural strength at 28 and 90 days age is 8% and 19% respectively.Hence, for the fly ash concrete with same workability, the increase in compressive strength is very marginal (2%); however, the increase in flexural strength is commendable (19%) compared to the basic mix.