Enhancing the addition of fly ash from thermal power plants in activated high belite sulfoaluminate cement

This study focuses on the activation of belite to promote the addition of solid industrial waste, such as fly ash (FA), as the supplementary component in high belite–sulfoaluminate cement (HBSC). The results indicate that the polymorph of belite, which transforms from β to α′, principally depends on the concentration of sodium tetraborate. The incorporation of FA into inactivated HBSC is very slow because the inactivated belite is unable to participate in the early hydration process to release calcium hydroxide (CH) and break the glass structure of FA. Compared with the inactivated belite, considerable hydration heat is released during the early hydration process in activated HBSC, in which a large amount of CH is present to promote the pozzolanic reaction of FA. In addition, (Na,Ca)8(Si,Al)12O24(SO4)2 is formed in the presence of sodium, which is a tectosilicate mineral with a bulk modulus that contributes to the compressive strength of the later period. The highest total content of FA in the activated HBSC, compared to inactive HBSC, improved from 5% to 12%. Thus, FA promotes the use of solid industrial waste and reduces the consumption of HBSC. Furthermore, the long term strength development with a large amount of FA can meet the requirements for engineering projects.