Fly ash degree of reaction in hypersaline NaCl and CaCl brines: Effects of calcium-based additives.

The pozzolanic reaction of fly ashes with calcium-based additives can be effectively used to solidify and chemically stabilize (S&S process) highly concentrated brines inside a cementitious matrix. However, complex interactions between the fly ash, the additive, and the brine typically affect the phases formed at equilibrium, and the resulting solid capacity to successfully encapsulate the brine and its contaminants. Here, the performances of two types of fly ash (a Class C and Class F fly ash) are assessed when combined with different additives (two types of cement, or lime with and without NaAlO), and two types of brine (NaCl or CaCl) over a range of concentrations (0 ≤ [Cl] ≤ 2 M).