Pulverised Fuel Ash (PFA), aka ‘Fly ash’ as a cement substitute.
PFA is a by-product of coal-burning power stations. As part of the combustion process, coal is pulverised into a powder before being burned. About 18% of the fuel forms fine glass spheres, about 75% of which rise with the flue gases from the combustion. The ‘ash’ is recovered from the gases and used, amongst other functions, as a cement substitute.
PFA is always used in conjunction with Portland Cement. It is employed in ratios ranging from 80% Pc and 20% PFA – 60% Pc and 40% PFA according to the ultimate function of the cement. PFA can’t be used completely as a substitute for cement, because it relies on the water and lime from the cement to hydrate as part of the overall chemical reaction.
In the future, as coal-burning power stations are phased out, PFA will gradually become unavailable.
Ground Granulated Blast-furnace Slag (GGBS) as a cement substitute
GGBS is a by-product of the iron and steel industry. In the blast furnace, slag floats to the top of the iron and removed. GGBS is produced through quenching the molten slag in water and then grinding it into...
[More]
Tags:
alternative bidg materials
Posted at: 02:33 PM | 0 Comments | Add Comment | Permalink
