TY - JOUR
T1 - Quantitative analysis of phase assemblage and chemical shrinkage of Alkali-activated slag
AU - Ye, Hailong
AU - Radlińska, Aleksandra
N1 - Publisher Copyright:
© Copyright 2016 Japan Concrete Institute.
PY - 2016
Y1 - 2016
N2 - This paper presents a quantitative analysis of hydrated phase assemblage and chemical shrinkage of alkali-activated slag (AAS) as a function of pH and modulus (n= SiO2/Na2O molar ratio) of activator. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermodynamic modeling, provide a comprehensive characterization of the phase assemblages and distribution in AAS microstructure. The main hydration products in AAS are calcium-alumina-silicate-hydrate (C-A-S-H) and hydrotalcite-type phases, while the formation of other hydrates is activator-dependent. For NaOH-activated slag, hydration products are preferentially formed around slag particles showing a hydrated rim, while for sodium silicate-activated slag, hydration products are initialized at both slag surface and inter-particle spaces simultaneously. However, a dark hydrated rim whose composition is similar to that of alkali-aluminosilicate-hydrate was observed around unhydrated slag in aged AAS. It indicates that the composition and spatial distribution of hydrates in AAS microstructure is heterogeneous, which cannot be predicted by thermodynamic modeling. The chemical shrinkage of AAS was quantified using buoyancy method and backscattered image analysis. The average chemical shrinkage of AAS is about 0.1211 ml/gslag and increases with the increasing modulus and pH of activator. The chemical shrinkage of AAS is about twice larger than that of portland cement, which may be attributed to the limited formation of expansive crystalline phases, such as ettringite and portlandite.
AB - This paper presents a quantitative analysis of hydrated phase assemblage and chemical shrinkage of alkali-activated slag (AAS) as a function of pH and modulus (n= SiO2/Na2O molar ratio) of activator. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermodynamic modeling, provide a comprehensive characterization of the phase assemblages and distribution in AAS microstructure. The main hydration products in AAS are calcium-alumina-silicate-hydrate (C-A-S-H) and hydrotalcite-type phases, while the formation of other hydrates is activator-dependent. For NaOH-activated slag, hydration products are preferentially formed around slag particles showing a hydrated rim, while for sodium silicate-activated slag, hydration products are initialized at both slag surface and inter-particle spaces simultaneously. However, a dark hydrated rim whose composition is similar to that of alkali-aluminosilicate-hydrate was observed around unhydrated slag in aged AAS. It indicates that the composition and spatial distribution of hydrates in AAS microstructure is heterogeneous, which cannot be predicted by thermodynamic modeling. The chemical shrinkage of AAS was quantified using buoyancy method and backscattered image analysis. The average chemical shrinkage of AAS is about 0.1211 ml/gslag and increases with the increasing modulus and pH of activator. The chemical shrinkage of AAS is about twice larger than that of portland cement, which may be attributed to the limited formation of expansive crystalline phases, such as ettringite and portlandite.
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U2 - 10.3151/jact.14.245
DO - 10.3151/jact.14.245
M3 - Article
AN - SCOPUS:84978066682
SN - 1346-8014
VL - 14
SP - 245
EP - 260
JO - Journal of Advanced Concrete Technology
JF - Journal of Advanced Concrete Technology
IS - 5
ER -