FLY ASHES REACTIVITY IN RELATION TO COAL COMBUSTION UNDER FLUE-GAS RECYCLING CONDITIONS

Samples of fly ashes generated from two different coals fired in a CO2 -rich atmosphere by recycling part of flue gas have been characterized for chemical composition and particle size distribution. They have al so been tested for reactivity against lime and gypsum in hydratory mix tures of interest in the held of pre-formed building materials. It has been found that firing coal in unusual conditions (mainly as far as f lame temperature and flue gas composition are concerned) does not alte r the reactivity of fly ashes in the systems referred to above. The ma in factor that affects fly ash reactivity is particle size distributio n, as for the ashes produced in ordinary air firing operations. (C) 19 97 Elsevier Science B.V.