BENEFICIAL USE OF FLY-ASH FROM CO-COMBUSTION OF LIGNITE AND WOOD PELLETS IN BLENDED CEMENT

摘要

Conventional coal fly-ash (CFA) and coal-biomass flyashesrn(CBFAs) were obtained at a thermoelectric powerrnstation (Atikokan, Ontario) from combustion of undilutedrnlignite and of lignite mixed with up to 62 wt% woodrnpellets. Co-combustion did not markedly change therncomposition of the fly-ash because of the very low ashrncontent of wood pellets compared to lignite. All fly-ashesrncontained less than 1 wt% carbon and thus complied withrnASTM regulations regarding carbon content for fly-ashrnuse in concrete. Partial substitution of cement with fly-ashrn(up to 40 wt%) had a moderate effect on the entrained airrncontent of mortars (up to 2.5 vol%), but this differencernvanished upon addition of air entraining agent (0.6 mL/kgrnof cementitous material). Substituted mortars exceededrn75% of the strength of ash-free mortar after 28 days ofrncuring, and, by 90 days, met or surpassed 100% of thernstrength of ash-free mortar.