Activation behavior of the novel CO₂ foaming agent for mining on fly ash

Although there have been many research results on the chemical activation of fly ash (FA) as a supplementary cementitious material (SCM) in cementitious materials. However, there is a lack of research on the use of CO₂ foaming agent (sodium bicarbonate and potassium aluminum sulfate) to activate fly ash. In this experiment, the effects of CO₂ foaming agent, sodium bicarbonate, and potassium aluminum sulfate on the activity of FA mixed paste were investigated. The mechanism of FA activation by activator was revealed by selective acid dissolution, QXRD, BSE-EDS statistical analysis, and quantitative analysis of TGA. The results showed that the remaining fly ash amounts of MG, SBG, and PASG after 28 days were 17.5%, 25.9%, and 43.3% lower than those of the control group, respectively. In addition, potassium aluminium sulphate promoted hydration to generate more CH to activate the FA. Sodium bicarbonate promoted hydration and produces more CH to activate FA by generating nano-CaCO₃. The mixture of sodium bicarbonate and potassium aluminum sulfate took advantage of both nano-CaCO₃ and potassium aluminum sulfate to promote silicate hydration to provide CH. As a result, the two synergistically activate FA. The above results show that CO₂ foaming agents can be used not only as foaming agents to prepare lightweight materials, but also as chemical activators to activate solid waste. This will have a high practical application value.