Effects of chemical admixtures and curing conditions on some properties of alkali-activated cementless slag mixtures

This paper reports the results of an investigation on the influences of admixtures and curing conditions on some properties of Alkali-Activated Slag (AAS) mixtures with no cement. In the study, Shrinkage-Reducing (SRA) and superplasticizing and setretarding (WRRe) admixtures were used. For the slag activation, sodium metasilicate was used at two sodium concentrations, 4% and 6% by mass of slag. Setting time, flow loss of fresh mixtures, and shrinkage strain, carbonation, flexural and compressive strength of hardened mixtures were measured. The test results showed that the admixtures generally had no impact on the setting times of AAS pastes. WRRe increased the flow rate of AAS mortars while SRA partially affected the flow values of AAS mortars. WRRe and SRA did not produce an important difference on the carbonation depths of AAS mortars. However, WRRe and especially SRA admixtures decreased the shrinkage values of AAS mortars. Additionally, curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to Normal Portland Cement (NPC) mortars, and the strength development of AAS mortars at early ages was very fast in comparison with NPC mortars when subjected to elevated temperature.