Influence of admixtures on the properties of alkali-activated slag mortars subjected to different curing conditions
Özet
This paper presents the influence of shrinkage-reducing (SHR) and superplasticizing and set-retarding
admixtures (SSRe) on the properties of slag pastes and mortars activated by liquid sodium silicate with
different dosage and modulus ratio. Properties in the fresh and hardened state for these binders were
investigated by means of measuring some properties including setting time, flowability, flexural strength,
compressive strength, carbonation and shrinkage. In this study, fifteen pastes and mortars were prepared.
Liquid sodium silicate was used to activate the slag at two sodium concentrations, 4% and 6% by mass of
slag. Liquid sodium silicate and sodium hydroxide were blended to obtain 0.75 and 1 modulus ratio of
SiO2/Na2O. Results showed that although the higher percentage of sodium in the activator produced a
higher strength, workability and setting times rapidly decreased with the higher sodium concentration
due to instantaneous reaction and quick hardening of slag activated by liquid sodium silicate. None of
the admixtures generally had an impact on the setting times of alkali-activated slag (AAS) pastes. SSRe
admixture increased the flow rate of AAS mortars while SHR admixture partially affected the flow values
of AAS mortars. SHR admixture exhibited a slight decrease in the carbonation depths of AAS mortars.
SSRe and particularly SHR chemical admixtures reduced the shrinkage of AAS mortars. However, the
shrinkage values of AAS mortars still were higher than those of ordinary Portland cement (NPC) mortars.
Curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to NPC mortars
