Strength and durability of cement with forest waste bottom ash

Every year more than 1 m3 of concrete is produced per person worldwide with cement accounting for 5–8% CO2 emissions and a growing use of mineral additions. Timber processing waste, a sustainable and renewable source for energy production, leads to significant amounts of wood-waste fly ash which has been used in concrete of acceptable strength and durability. Grate operated wood waste power plants produce immense volumes of bottom-ash, not studied to date. This study focused on characterising ground bottom-ash (GWA) with strength and durability assessment as cement replacement in mortar. Durability-related properties tested at 80 days generally revealed marginal loss but from around 3 months, strength surpassed control attaining 12% higher values at 1 year. Although tested nonpozzolanic due to crystallinity, GWA may be used as filler in cement-based materials further contributing to sustainable construction.

► Grate operated biomass power-plants produce bottom-ash (WA), not studied to date.
► Ground WA (GWA) was used as a cement (5% and 10%) replacement in paste and mortar.
► Hydration was observed on paste with a novel technique Cryo SEM.
► GWA mortar showed marginal durability loss but improved strength at later ages.
► GWA, non-glassy, may be used as a filler, contributing to sustainable construction.