Understanding the reactivity of biomass ash from a pulverised fuel combustor

The manuscript provides long-term microstructural study on as-collected wood biomass ash (WBA) from a pulverised fuel combustor. Analytical methods, including isothermal calorimetry, X-ray powder diffraction, thermogravimetric analysis, and mercury intrusion porosimetry, were used to assess reaction kinetics, phase development, and porosity. Results show that WBA increases water demand due to its irregular particle morphology and high content of unburnt carbon and carbonates, causing a dilution effect that delays hydration reactions and extends the induction period. Microstructural analysis revealed significant changes in porosity, with an increase in pores between 0.01–0.05 μm during early hydration. As a result, early mechanical strength is reduced. Over time, the pozzolanic activity and carbonation of WBA enhance compressive strength, improving long-term performance. The study highlights the potential of WBA as a sustainable cement substitute and emphasises the need for further research to optimise its integration into concrete applications and assess its durability in various environments.