FLY ASH

WHAT IS FLY ASH?

Fly ash is produced from the burning of pulverized coal in a coal-fired boiler. It is a fine-grained, powdery particulate material that is carried off in the flue gas and normally collected from the flue gas by means of electrostatic precipitators , baghouses, or mechanical collection devices such as cyclones.

Fly ash is commonly used in production of concrete. It is applied as a supplementary cementing material. Initially the idea was to use fly ash for economical reasons – on one hand to utilize fly ash which is an industrial by product, on the other to reduce the amount of costly cement. However, it appears that application of fly ash in concrete has a lot of benefits, mainly by reduction of unwanted hydration heat.

Cement can be replaced with fly ash in concrete. It reacts (Si) with Ca(OH)2 and produces more CSH gel which contributes to strength. With reduced cement, hydration heat will be reduced and hence there is strength gain.