Influence of different additives on the properties of sodium sulfate activated slag

• Activated slag blended with 5% limestone showed the highest workability.
• Activated slag blended with 5% SF or limestone showed high compressive strength.
• Activated slag blended with 5% Portland cement showed the lowest compressive strength.
• Activated slag blended with 5% Portland cement showed the lowest drying shrinkage.
• Activated slag blended with 5% silica fume showed the highest drying shrinkage.

In this work, the effect of some additives namely condensed silica fume (SF), fly ash (FA), limestone (LS), hydrated lime (HL) and Portland cement (PC) on the workability, compressive strength and drying shrinkage of 1% Na2O equivalent of Na2SO4 activated granulated ground blast-furnace slag (hereafter referred to as slag) has been investigated and compared to slag activated with other common activators. These additives were used as a partial replacement of slag at level of 5%, by weight. Traditional neat PC and activated neat slag (AS0) pastes were used as references. The various decomposition phases formed were identified using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Compared to AS0, the results indicated that the inclusion of LS increased the workability, whilst HL, FA, PC and SF reduced it. The inclusion of SF and LS enhanced the compressive strength, whilst FA, HL and PC decreased it. The inclusion of FA, HL, PC and LS reduced the drying shrinkage, whilst SF greatly increased it.