A review on the characteristics of wood biomass fly ash and their influences on the valorization in cementitious materials

Wood biomass fly ash (WBFA) has emerged as one of the most dominant by-products in the biomass energy sector. Circulating WBFA for construction practice can mitigate the secondary pollution caused by improper ash management, and provide a new material source to compensate for the scarcity of raw materials in the construction industry. This paper reviewed the current research progress on recycling WBFA in cementitious materials. The physicochemical properties of WBFA were summarized based on the literature. Further, the implementations of WBFA for the development of cementitious materials were categorized into three binder systems: clinker, blended cement, and alkali-activated materials (AAMs). Owing to the large variation in chemical compositions of WBFA and strict requirements in clinkering parameters, employing WBFA in blended cement and AAMs seems to be more promising. A new classification approach for WBFA was proposed to divide WBFA into two categories. This helps to provide simple guidance for ash recycling in construction practice. Finally, the current research gaps in WBFA valorization in cementitious materials were summarized, outlining the research for further exploration.