Abstract :
[en] Woody biomass ashes (WBAs), originating from the combustion of lignocellulosic residues, are increasingly considered as promising supplementary cementitious materials (SCMs) due to their potential to replace a portion of Portland cement and reduce environmental impact. However, their direct incorporation in cement-based systems is limited by challenges, including low amorphous content, poor reactivity, high levels of alkalis and soluble salts, and variability in chemical composition depending on the biomass source and combustion conditions. To address these limitations, this study investigates the application of two treatment techniques—mechanochemical activation (MCA) and water-washing—to improve the physicochemical and mineralogical properties of WBAs and enhance their suitability for cementitious use.
Mechanochemical activation was employed to induce structural changes through high-energy grinding, aiming to reduce particle size, increase specific surface area, and partially amorphize crystalline phases, thereby promoting pozzolanic reactivity. In parallel, water washing was applied as a purification method to extract soluble salts and alkalis, which negatively affect setting behaviour, durability, and environmental compatibility. The treatments were applied separately to ashes obtained from different facilities, and their effects were analysed through a comprehensive characterization approach, including X-ray diffraction, thermogravimetric analysis, pH and electrical conductivity measurements, leaching tests, and pozzolanic reactivity assessments based on lime consumption and strength activity index.
The results indicate that both treatment methods significantly alter the properties of WBAs, each contributing to performance improvement in different ways. While MCA enhances reactivity by increasing amorphous content and promoting the formation of reactive silicate phases, water washing stabilizes chemical composition by removing undesirable soluble components. Furthermore, the potential benefits of combining these treatments are discussed, highlighting the possibility of designing optimized multi-step processing routes tailored to the specific characteristics of the ash source. This study provides a foundation for the valorization of WBAs as reactive and environmentally compatible SCMs in sustainable construction materials.
