Pore solution composition and solubility of alkali-activated fly ash

Abstract

Pore solution of hardened alkali-activated fly ash paste was extracted by the steel-die method. The aqueous phase composition of pore solution was analyzed using ICP-OES analysis technique. The results show that the concentrations of Si, Al, Ca, K and OH^- decrease with curing time regardless of the curing temperatures (40°C/60°C) and alkaline activators (sodium hydroxide with/without sodium silicate). On the contrary, the concentration of S increases with curing time. A higher temperature curing decreases the solubility of Si, Al, Ca and K in the alkali-activated fly ash, while it doesn’t show much influence on the solubility of S. The plot of the concentration of Al versus the concentration of Si displays a quasi-linear logarithmic relationship. This relationship implies congruent removal of Si and Al from the frameworks of fly ash.