Analysis of cubic and orthorhombic C3A hydration in presence of gypsum and lime

Kirchheim, Ana Paula; Fernàndez-Altable, Víctor; Monteiro, Paulo J.M.; Molin, Denise Carpena Coitinho Dal; Casanova, I.

doi:10.1007/s10853-009-3292-3

Cited by 55 publications

(39 citation statements)

References 16 publications

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“…This study is part of a larger work [10] that includes the study of these materials in other conditions and using other techniques. Also some previous results were published by Kirchheim et al [11].…”

Section: Introductionmentioning

confidence: 72%

“…For the orthorhombic samples, the higher the sulfate concetration, the smaler are the ettringite size, the longer are the time to exaust the reaction. Corroborating, but in diferent mixture proportions, Kirchheim et al [11] showed that, in a SEM study, the ettringite crystals, when based on the size and the consumption of C 3 A and gypsum, orthorhombic C 3 A pastes presented a faster rate of formation of crystals, which were also longer. Real time Rheometric measurements showed that orthorhombic C 3 A mixes presented higher increase of stiffness than cubic C 3 A at very early stages of hydration which can be adressed to a higher reactivity of the orthorhombic C 3 A in presence of sulfates.…”

Section: C) Initial Solution/aluminate Ratio = 50 Ml/gmentioning

confidence: 99%

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Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

et al. 2011

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This study details the differences in real-time hydration between pure (cubic) and Na-doped (orthorhombic) C 3 A. First, pure phases were synthesized in the laboratory to develop an independent benchmark for the reactions, then the reactions of others phases were isolated. Because the kinetics of this reaction moves extremely quickly, most methods are not adequate to study the reactions in the early phases. Here, a high-resolution full-field soft X-ray imaging technique operating in the X-ray water window was used to capture the mechanism of the C 3 A hydration. The results show that there are differences in the hydration mechanism of each type of C 3 A, dependent on the concentration of sulfates ions in solution. The reactions with cubic C 3 A (pure) seems to be more susceptible to higher concentrations of sulfate ions by forming smaller ettringite needles at a slower pace than the orthorhombic C 3 A (Na-doped) sample.Keywords: tricalcium aluminate, hydration, hydration products, ettringite, image analysis IntroductionThe properties of clinkers are strongly affected by the quantity and composition of the clinker phases [1], which can drive the kinetic process of hydration. The hydration of C 3 A is an important stage in the overall hydration of cement because it has considerable influence on its setting and early hardening. The hydration of C 3 A is far more strongly affected by environment conditions than that of C 3 S and, in particular, by the presence of other substances with which it can react [8]. The reaction of C 3 A with water is a primary consideration. Calcium aluminate hydrates (e.g., C 3 AH 6 , C 4 AH 19, and C 2 AH 8 ) form quickly and liberate large amounts of heat [9]. If the very rapid and exothermic hydration of C 3 A is allowed to proceed unhindered in cement, then the setting occurs too quickly and the cement paste does not develop strength. Therefore, calcium sulfate is added to slow down the C 3 A hydration. In the presence of gypsum, C 3 A forms needle-like ettringite. Thus, for practical purposes, it is not the hydration reaction of C 3 A alone that is important but the hydration reaction of C 3 A in presence of gypsum (sulfates). The reactivity of C 3 A in clinker and the availability of sulfate in solution control the setting characteristics of concrete, making these compounds ideal for addressing probable setting problems.Because of the high contents of C 3 A in some cement, special attention must be paid to the mineralogy and reactivity of this phase. Industrial clinkers and their phases contain minor elements such as Na 2 O, K 2 O, SO 3, and Cl -, which may be attributed to several sources, such as raw materials, fuel and/or the lining of the kilns. Alkalis can be incorporated into a number of phases of the clinker and often Na 2 O is

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Section: Introductionmentioning

confidence: 72%

Section: C) Initial Solution/aluminate Ratio = 50 Ml/gmentioning

confidence: 99%

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

et al. 2011

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“…Thus, formation of those phases may significantly affect further sorption of water vapour by cement. Furthermore, Kirchheim et al (2009) showed that there are important differences between the hydration of the two C 3 A polymorphs (cubic and orthorhombic) with gypsum. Therefore, it is of interest to have a better understanding of the interaction of each C 3 A polymorph with calcium sulfates when exposed to different relative humidities.…”

Section: Introductionmentioning

confidence: 99%

Impact of environmental moisture on C₃A polymorphs in the absence and presence of CaSO₄ · 0·5 H₂O

Dubina

Plank

Black

et al. 2014

Advances in Cement Research

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The phenomenon of water vapour sorption by anhydrous C 3 A polymorphs both in the absence and in the presence of CaSO 4 . 0 . 5 H 2 O was studied utilising dynamic and static sorption methods. It was found that orthorhombic C 3 A starts to sorb water at 55% relative humidity (RH) and cubic C 3 A at 80% RH. Also, C 3 A o sorbs a higher amount of water which is predominantly physically bound, whereas C 3 A c preferentially interacts with water by chemical reaction. In the presence of calcium sulfate hemihydrate, ettringite was observed as the predominant pre-hydration product for both C 3 A modifications: that is, ion transport had occurred between C 3 A and sulfate. Environmental scanning electron microscopic imaging revealed that in a moist atmosphere, a liquid water film condenses on the surface of the phases as a consequence of capillary condensation between the particles. C 3 A and sulfate can then dissolve and react with each other. Seemingly, pre-hydration is mainly facilitated through capillary condensation and less through surface interaction with gaseous water molecules. Notation

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“…This can occur when the rate of ettringite crystallisation is greater than the dissolution rate of the candidate ions. Considering the almost instantaneous hydration of the cement clinker phase of tricalcium aluminate -C 3 A, by the topochemical mechanism [Kirchheim et al, 2009], the dissolving aluminate ions Al(OH) 4 -cannot migrate far into the pore solution, because the supersaturation of the liquid phase with respect to ettringite is so low. By this mechanism, damage occurs when the regions of crystal growth intersect and mutually exert pressure, forcing the particles apart [Cohen, 1983].…”

Section: Introductionmentioning

confidence: 99%

The role of ettringite in the deterioration of artificial lime stabilised soils: a microstructural study

Buttress

Grenfell

Airey

2013

Road Materials and Pavement Design

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ABSTRACT. The formation of ettringite has been defined as a major failure mechanism of lime stabilised cohesive soils. It can result in both disruptive volumetric changes and loss of mechanical strength. The mechanisms of its formation and the role it plays in deleterious processes are complex. This paper reports the dimensional and strength changes of a range of artificial lime stabilised cohesive soils subject to two swell test procedures: the UK linear CBR swell test (BS1924-2, BSI 1990) and the European accelerated swell test (EN13286-49, CEN 2007). The resulting microstructural composition was analysed using a combination of Scanning Electron Microscopy and Electron Dispersive X-ray Spectroscopy (SEM-EDX). The results are explained in terms of established theories of crystal formation and subsequent expansion mechanisms.

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Analysis of cubic and orthorhombic C3A hydration in presence of gypsum and lime

Cited by 55 publications

References 16 publications

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

Impact of environmental moisture on C₃A polymorphs in the absence and presence of CaSO₄ · 0·5 H₂O

The role of ettringite in the deterioration of artificial lime stabilised soils: a microstructural study

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Analysis of cubic and orthorhombic C3A hydration in presence of gypsum and lime

Cited by 55 publications

References 16 publications

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C3A in the Presence of Sulfates

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C3A in the Presence of Sulfates

Impact of environmental moisture on C3A polymorphs in the absence and presence of CaSO4 · 0·5 H2O

The role of ettringite in the deterioration of artificial lime stabilised soils: a microstructural study

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Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

Impact of environmental moisture on C₃A polymorphs in the absence and presence of CaSO₄ · 0·5 H₂O