Beneficial Use of Fly-Ash from Co-Combustion of Lignite and Wood Pellets in Blended Cement

A. Johnson, S. Kinrade, and L.J.J. Catalan (Canada)

Keywords

Flyash; biomass cocombustion; cement mortar; compressive strength; entrained air

Abstract

Conventional coal fly-ash (CFA) and coal-biomass fly-ashes (CBFAs) were obtained at a thermoelectric power station (Atikokan, Ontario) from combustion of undiluted lignite and of lignite mixed with up to 62 wt% wood pellets. Co-combustion did not markedly change the composition of the fly-ash because of the very low ash content of wood pellets compared to lignite. All fly-ashes contained less than 1 wt% carbon and thus complied with ASTM regulations regarding carbon content for fly-ash use in concrete. Partial substitution of cement with fly-ash (up to 40 wt%) had a moderate effect on the entrained air content of mortars (up to 2.5 vol%), but this difference vanished upon addition of air entraining agent (0.6 mL/kg of cementitous material). Substituted mortars exceeded 75% of the strength of ash-free mortar after 28 days of curing, and, by 90 days, met or surpassed 100% of the strength of ash-free mortar.

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