Activation of Ground Blast‐Furnace Slag by Alkali‐Metal and Alkaline‐Earth Hydroxides

Roy, Amitava; Schilling, Paul J.; Eaton, H. C.; Malone, Philip G.; Brabston, W. Newell; Wakeley, Lillian D.

doi:10.1111/j.1151-2916.1992.tb04416.x

Cited by 65 publications

(30 citation statements)

References 9 publications

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“…The main reaction product formed is a C-A-S-H gel whose composition (lower Ca/Si ratio: 1-1.2) and structure vary from the typical C-S-H formed from OPC. A number of secondary products may form, including hydrotalcite, calcite and bases such as AFm, depending on activator type and concentration, slag structure and composition, and the curing conditions under which the paste hardens (11,(31)(32)(33)(34)(55)(56)(57)(58). The microstructure of the gels formed during slag activation has been explored by several authors (53,55,(59)(60)(61)(62)(63)(64)(65).…”

Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

A review on alkaline activation: new analytical perspectives

et al. 2014

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For many years now the idea of including alkalis in a Portland cement matrix has been regarded as a daft or inexcusably erroneous proposition: despite its absurdity, that opinion has been widely accepted as a basic premise by the scientific and technical community working in the area of the chemistry of cement. In 1957 Glukhovsky proposed a working hypothesis in which he established a close relationship between alkalis and cementitious materials. That hypothesis has become consolidated and has served as a basis for developing a new type of binders, initially called "alkaline cements". The present paper reviews the most significant theoretical interpretations of the role played by alkalis in the formation of the "stony" structure of cement. It ends with a broad overview of the versatility of this type of materials for industrial applications and a discussion of the possibility of building on the existing legislation to meet the need for the future regulation of alkaline cement and concrete manufacture. RESUMEN: Activación alcalina: Revisión y nuevas perspectivas de análisis.Hace algunos años, la sola idea de la presencia de álcalis en una matriz de cemento Portland se consideraba casi como una aberración, o como un error imperdonable; convirtiéndose en un postulado básico (absurdo) ampliamente aceptado por la comunidad científica y técnica vinculada a la química de los cementos. En 1957 Glukhovsky propuso una hipótesis en la que se establecía una estrecha relación entre los álcalis y los materiales cementantes. Hoy día nadie duda de que dicha hipótesis ha servido de base para el desarrollo de una nueva clase de materiales cementantes: "cementos alcalinos". En el presente trabajo se hace una revisión sobre los aspectos teóricos más relevantes del papel de los álcalis en la formación de estos conglomerantes. También se da una visión genérica de su versatilidad, desarrollo industrial y estado de la normativa actual para regular en el futuro la fabricación de cementos y hormigones alcalinos.

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Section: Fundamentals Of Alkaline Activation In Calcium-rich Systems:mentioning

confidence: 99%

A review on alkaline activation: new analytical perspectives

et al. 2014

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“…According to [7], the slag activation process begins with a destruction of the slag bonds (e.g., Ca-O, Mg-O, Si-O-Si, Al-O-Al and Al-O-Si) followed by the formation of a Si-Al layer all over the surface of slag grains and finally, the formation of the hydration products such as C-S-H and hydrotalcite [4]. pH is reported to be the major factor controlling the slag activation process (rather than the activating cation) with higher pH environment inducing better slag activation and higher mechanical strength [4,8,9]. Numerous research efforts have focussed on the activation of GGBS by various alkali-metal hydroxides and silicates such as NaOH, KOH or alkali salts such as waterglass and Na 2 SO 4 and their mixtures [4].…”

Section: Introductionmentioning

confidence: 99%

Strength and hydration properties of reactive MgO-activated ground granulated blastfurnace slag paste

Jin

Al‐Tabbaa

2015

Cement and Concrete Composites

253

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a b s t r a c tGround granulated blastfurnace slag (GGBS) is widely used as a partial replacement for Portland cement or as the major component in the alkali-activated cement to give a clinker-free binder. In this study, reactive MgO is investigated as a potentially more practical and greener alternative as a GGBS activator. This paper focuses on of the hydration of GGBS, activated by two commercial reactive MgOs, with contents ranging from 2.5% to 20% up to 90 days. The hydration kinetics and products of MgO-GGBS blends were investigated by selective dissolution, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy techniques. It was found that reactive MgO was more effective than hydrated lime in activating the GGBS based on unconfined compressive strength and the efficiency increased with the reactivity and the content of the MgO. It is hence proposed that reactive MgO has the potential to serve as an effective and economical activator for GGBS.

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“…On the other hand, significant amount of work has been done on characterizing the hydrated phases of AAS as a function of initial pH and dissolved silicate ([SiO 2 ] aq ) content of activator. The pH in NaOH solution also affects the structure of C-A-S-H and fraction of other crystalline phases (Roy et al 1992). The incorporation of ([SiO 2 ] aq ) can lower the crosslinking of C-A-S-H structure as observed by 29 Si nuclear magnetic resonance (NMR), and reduce the crystallinity in hydrated phases as observed in XRD (Bonk et al 2003;Brough and Atkinson 2002;.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of Phase Assemblage and Chemical Shrinkage of Alkali-Activated Slag

Radlińska

2016

ACT

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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= SiO 2 /Na 2 O 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/g slag 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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Activation of Ground Blast‐Furnace Slag by Alkali‐Metal and Alkaline‐Earth Hydroxides

Cited by 65 publications

References 9 publications

A review on alkaline activation: new analytical perspectives

A review on alkaline activation: new analytical perspectives

Strength and hydration properties of reactive MgO-activated ground granulated blastfurnace slag paste

Quantitative Analysis of Phase Assemblage and Chemical Shrinkage of Alkali-Activated Slag

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