Wood Ash-Based Low-Carbon Cementitious Composites

Concrete is a huge emitter of CO₂. About 900 kg of CO₂ is emitted to produce 1000 kg of cement, concrete’s main ingredient. To reduce the carbon footprint of cement, supplementary cementitious materials (SCM) are adopted as a partial replacement. Coal fly ash is a popularly used SCM to replace cement in concrete; however, coal industries are being shut down globally because of the negative environmental impact, resulting in the scarcity of coal fly ash. Wood ash, a byproduct of bioenergy found in abundance in the timber-based construction industry in western Canada, has the potential to serve as a substitute for coal fly ash. Including wood ash in concrete solves the disposal issue of the abundant wood ash produced as well. This study evaluates the performance of wood ash-based cementitious composites considering their compressive strength and setting time results. There are two types of ash produced from burning wood, wood fly ash (WFA) and wood bottom ash (WBA). Being the finer ash, WFA replaced cement, and the coarser WBA replaced sand at 15, 30, 45%, and 15, 30% levels, respectively. It was observed that the combination of 15% WFA and 15% WBA provided a comparable result with the reference mortar based on the compressive strength.