Does wood fly ash (WFA) have pozzolanic property? A study on low- and high-temperature partially burnt WFA compared to classes C and F coal fly ash (CFA)
Rubaiya Rumman, M. Shahria Alam
Abstract
This study investigates the potential of utilizing wood fly ash (WFA) as a sustainable supplementary cementitious material (SCM) to replace coal fly ash (CFA) in concrete production. As coal power plants shut down, the availability of the popular SCM CFA is depleting, necessitating alternative materials. This research evaluates the reactivity and pozzolanic activity of WFA burnt at high temperatures (HW) and low temperatures (LW) compared to commercially available classes C CFA (CC) and F CFA (CF). WFA samples had coarser particle sizes than CFA, with HW having smaller particles. The oxide composition analysis showed that LW had more pozzolanic oxides, while HW had higher CaO content, suggesting LW would be more pozzolanic and HW more hydraulic. XRD results indicated lower amorphous content in WFA samples compared to CFA, with LW and HW having 27 % and 24 %, respectively, versus 65 % and 87 % for CC and CF. Despite this, both WFA samples demonstrated pozzolanic properties, reducing Ca(OH) 2 content and participating in the hydration process. WFA decreased the workability and setting time of fresh paste mixtures due to its angular and porous nature, with HW being more water absorbent. The findings highlight the challenges and benefits of using WFA in concrete. With the increasing need for sustainable energy sources and the disposal challenges of wood ash, this study suggests that WFA can be a viable substitute for CFA, promoting sustainable and green concrete solutions. This transition is crucial for achieving net-zero emission goals and addressing the disposal issue of increased wood ash production. • The wood fly ash (WFA) had less amorphous content than the coal fly ash (CFA). • The lower temperature burnt WFA (LW) of this study had more pozzolanic oxide. • The higher temperature burnt WFA (HW) of this study had more CaO. • LW and HW of this study had more pozzolanic property and hydraulic property, respectively. • Grinding the WFA is expected to improve its reactivity.