Mechanisms and parameters controlling the tricalcium aluminate reactivity in the presence of gypsum

Minard, H.; Garrault, Sandrine; Regnaud, Laure; Nonat, André

doi:10.1016/j.cemconres.2007.06.001

Cited by 294 publications

(249 citation statements)

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“…Silva and Monteiro [16] also observed the ettringite growth on or near the C 3 A surface. On the other hand, Minard et al [23] assumed that while the slow process of ettringite formation could be limited by ettringite growth rate, its dependence on the surface area of C 3 A indicated that it is limited by dissolution of C 3 A.…”

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

confidence: 99%

“…Minard et al [23] described that even with different C 3 A reactivity, the time necessary to exhaust the totality of the sulfate ions does not evolve in a linear way with the quantity of gypsum initially introduced. In the present research, the hydration of cubic C 3 A (pure) seems to be more susceptible to the presence of higher concentration of sulfate ions -considering less C 3 A particles in solution for the same initial sulfate concentration.…”

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

confidence: 99%

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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“…For example, it is well established that at the early stage of its hydration with liquid water, C 3 A can react with sulfates to form AF m or AF t phases (Black et al, 2006;Brown et al, 1984;Minard et al, 2007;Pourchet et al, 2009). Thus, formation of those phases may significantly affect further sorption of water vapour by cement.…”

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 is, in principle, an expected result: Taylor already reported that less ettringite was formed in a low-C 3 A cement (9). However, this argument is currently a matter of controversy, and the study of the detailed mechanisms controlling C 3 A reactivity in the presence of sulfates has only recently started to be addressed (11).…”

Section: Expansive Behaviormentioning

confidence: 99%

Un estudio combinado respecto a la evolución de la expansión y la resistencia a tracción de morteros bajo el ataque sulfático: implicaciones en el diagnóstico de durabilidad

Akpınar¹,

Casanova²

2010

Mater. construcc.

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Mechanisms and parameters controlling the tricalcium aluminate reactivity in the presence of gypsum

Cited by 294 publications

References 8 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

Un estudio combinado respecto a la evolución de la expansión y la resistencia a tracción de morteros bajo el ataque sulfático: implicaciones en el diagnóstico de durabilidad

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Mechanisms and parameters controlling the tricalcium aluminate reactivity in the presence of gypsum

Cited by 294 publications

References 8 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

Un estudio combinado respecto a la evolución de la expansión y la resistencia a tracción de morteros bajo el ataque sulfático: implicaciones en el diagnóstico de durabilidad

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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