Influence of activator type and slag volume fraction on properties of alkali-activated slag pastes

Alkali-activated systems belong to the group of alternative inorganic binders in which the binder properties are dictated by both the aluminosilicate precursor and alkaline activator. In this work, blast furnace slag and three different alkaline activators, namely sodium hydroxide, sodium water glass, and sodium carbonate, were selected. An innovative mixture design based on the same concentration of alkali (Na+) of 4 mol/dm(3) for all activators and different volume fractions of slag in pastes, ranging from 0.44 to 0.54, was investigated by the flow table test, compressive and flexural strength test, and by a shrinkage test under autogenous conditions. Great differences for various activators for all investigated parameters were obtained. The highest fluidity, regardless of volume fraction of the slag, was observed for the water glass, originating from a greatly decreased yield stress compared to the two other activators. The type of activator and the volume fraction of the slag also played a crucial role in the development of shrinkage and strength.