Thermodynamic modeling and experimental study of alkali-activated slag paste

A newly developed thermodynamic approach was introduced from the literature to investigate the influence of NaOH content on the hydrate assemblage and chemistry of aqueous solution of activated slag paste (Na2O/slag=4%, 6% and 8%). The ICP-OES test was performed to obtain the aqueous species profiles such as Si, Ca, Al and Na etc. The elemental concentrations in aqueous solution show a similar trend between thermodynamic calculations and experimental results. The modeling results showed that the influence of NaOH content on the uptake of Na into the primary reaction products and chemical shrinkage depends on slag reaction extent and NaOH content. The NaOH content does not show an obvious influence on the porosity development. The volume fraction of primary products in total products is between 40% and 60%, and particularly increases slightly after a certain degree of reaction for activated slag with Na2O/slag=4% and 6%. The volume ratio between total products and reacted slag is around 1.5~1.7, smaller than the value from 2.06 to 2.2 reported for Portland cement.