Reuse of wood ash from biomass combustion in non-structural concrete: mechanical properties, durability, and eco-efficiency

Wood biomass fly ash can contribute to a more sustainable urban infrastructure, but requires efficient recycling strategies. This paper investigates the mechanical properties, durability, and eco-efficiency of non-structural concrete produced with 15% and 30% of portland cement replaced by wood biomass fly ash under combined effects of w/b ratio, ash content, and curing age. Two post-treatment to improve ash reactivity (grinding and grinding followed by re-calcining) were investigated. Concrete series with 15% ash presented higher relative compressive strength than 30% series regardless of the w/b ratio. Concrete mixtures produced with a w/b ratio of 0.35 did not reach the reference compressive strength regardless of the ash content. The ash re-calcining did not improve the concrete durability and mechanical properties. The carbonation increased in blended mixtures, but at acceptable levels. The absorption by capillarity increased overmuch in blended mixtures with re-calcined ash. The energy demand for re-calcining reduced the concrete eco-ecoefficiency. Concrete produced with 30% ash are less eco-efficient than those produced with 15%, except for w/b ratio of 0.35 due to the high cement consumption. These results can support industries to find innovative solutions for a broader wood ash valorization and support the development of a more sustainable urban infrastructure.