Influence of Na(2)O Content and Ms (SiO(2)/Na(2)O) of Alkaline Activator on Workability and Setting of Alkali-Activated Slag Paste

The performance of alkali-activated slag (AAS) paste using activators of strong alkali components is affected by the type, composition, and dosage of the alkaline activators. Promoting the reaction of ground granulated blast furnace slag (GGBFS) by alkaline activators can produce high-strength AAS concrete, but the workability might be drastically reduced. This study is aimed to experimentally investigate the heat release, workability, and setting time of AAS pastes and the compressive strength of AAS mortars considering the Na(2)O content and the ratio of Na(2)O to SiO(2) (Ms) of binary alkaline activators blended with sodium hydroxide and sodium silicate. The test results indicated that the AAS mortars exhibited a high strength of 25 MPa at 24 h, even at ambient temperature, even though the pastes with an Na(2)O content of ≥6% and an Ms of ≥1.0 exhibited an abrupt decrease in flowability and rapid setting.