Thermal Decomposition of Hydrated Alumina Cement (CAH10)

Guirado, F.; Galí, Salvador; Chinchón, J. S.

doi:10.1016/s0008-8846(98)00007-6

Cited by 51 publications

(8 citation statements)

References 24 publications

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“…The thermograms for the phosphate-modified CAC samples (Figure 4), show considerably different behaviour from the unmodified CAC samples (Figure 3). These samples exhibit three main weight losses, at ~90, 230 and 280°C, with broad peaks in the derivative curves consistent with non-crystalline water environments [38]. This is in agreement with the XRD results ( Figure 2B) which did not show the formation of any crystalline hydrates in phosphate-modified CAC.…”

Section: Thermogravimetrysupporting

confidence: 91%

“…The gel phase present also dehydrates over a broad temperature range, partially overlapping with the dehydration of the CAH 10 , which further complicates the peak assignment [1]. The composition of this gel phase even in the unmodified CAC system is not fully understood, as it remains unclear whether this phase is a hydrated alumina gel (AH n ) [27,37] or a calcium aluminium hydrate (C-A-H) type gel [35,38,39].…”

Section: Thermogravimetrymentioning

confidence: 99%

“…The broad temperature range over which this weight loss takes place suggests low crystallinity, which is why this phase was not detected by XRD. Regarding the intermediate temperature weight loss (centered at ∼230°C), Guirado et al [38] identified that dehydration of CAH 10 occurs in several stages, including a mass loss at 225°C associated with the dehydration of the amorphous portion (denoted CAH y by those authors). It is possible that the mass loss observed in this temperature range in the phosphate-modified CAC may, analogously to that described by Guirado et al [38], result from an initially disordered aluminate phase.…”

Section: Thermogravimetrymentioning

confidence: 99%

See 2 more Smart Citations

Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

Chavda

Bernal

Apperley

et al. 2015

Cement and Concrete Research

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The conversion of hexagonal calcium aluminate hydrates to cubic phases in hydrated calcium aluminate cements (CAC) can involve undesirable porosity changes and loss of strength.Modification of CAC by phosphate addition avoids conversion, by altering the nature of the reaction products, yielding a stable amorphous gel instead of the usual crystalline hydrate products. Here, details of the environments of aluminium and phosphorus in this gel were elucidated using solid-state NMR and complementary techniques. Aluminium is identified in both octahedral and tetrahedral coordination states, and phosphorus is present in hydrous environments with varying, but mostly low, degrees of crosslinking. A 31 P/ 27 Al rotational echo adiabatic passage double resonance (REAPDOR) experiment showed the existence of aluminium-phosphorus interactions, confirming the formation of a hydrated calcium aluminophosphate gel as a key component of the binding phase. This resolves previous disagreements in the literature regarding the nature of the disordered products forming in this system.

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Section: Thermogravimetrysupporting

confidence: 91%

Section: Thermogravimetrymentioning

confidence: 99%

Section: Thermogravimetrymentioning

confidence: 99%

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Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

Chavda

Bernal

Apperley

et al. 2015

Cement and Concrete Research

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“…High temperature ESEM observations reveal microcrack initiation, particularly at interfaces between the aggregates and the matrix. This must be related to hydrate conversion and dehydration processes that have been previously identified as operating in this temperature range [1,3,5,9,10]. Fig.…”

Section: Discussionmentioning

confidence: 91%

Characterisation of microstructural evolutions in refractory castables by in situ high temperature ESEM

Marzagui

Cutard

2004

Journal of Materials Processing Technology

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This paper deals with the characterisation of the microstructural evolutions during the first heating of two commercial refractory castables by dilatometry and by in situ high temperature environmental scanning electron microscopy (HT-ESEM) up to 1300 • C. Investigations have been made both on the castables and on their respective matrix. Effects of microstructural changes have been observed on dilatometric results. Four temperature domains could be defined, in which shrinkage is occurring. During in situ HT-ESEM observations, important microstructural changes could be seen in these four temperature domains. They deal first with microcrack initiation due to dehydration mechanisms. Microcrack opening then increases when increasing the sample temperature. An acceleration of these microcrack-opening mechanisms was observed when sintering starts in the 800-950 • C temperature range. Between 1000 and 1100 • C, liquid phases appear in the material and liquid phase sintering starts to occur. An increase of the liquid phase amount and of liquid phase sintering effects are observed when increasing temperature up to 1300 • C. Crystal growth was identified as occurring at this temperature too. Above 1100 • C, a competition between shrinkage mechanisms and expansion ones take place. The balance between these two types of mechanisms is not the same for the two studied refractory castables.

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“…Besides, some ultrafine particles of Ca(OH)2, Mg(OH)2, calcite and dolomite could have been consumed by the continuous formation of ettringite and C-S-H gel [32]. This is reflected by the TG curve in Figure 5(b), on which the total weight loss between 400°C and 1000°C is 1.5% more than that in Figure 5.…”

Section: Dsc-tg Analysismentioning

confidence: 97%

On High-Strength Low-Shrinkage Iots-Based Concrete

Geng¹,

Wen²,

Wu³

et al. 2016

IJHT

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With iron ore tailings (IOTs) as the main raw material, the author prepares concrete specimens featuring low shrinkage and high bending strength, and reduces the shrinkage with "hot steaming" steel slag as the admixture. Then, the author carries out a series of laboratory tests to characterize the shrinkage, strength, morphology, microstructure and chemical components of the specimens during the curing process. These parameters are measured after 12 hours, 3 days, 7 days and 28 days, respectively. For each mixture, 3 replicates are prepared and analyzed by the strength test, X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The measured shrinkage of the proposed concrete is lower than half of that of the normal concrete for railway sleepers, and its bending strength is almost twice of that of the latter. Further investigation demonstrates that the large decrease in the autogenous shrinkage is attributable to the micro-expansion, which is caused by the hydration of f-CaO, f-MgO and RO phases in the highly dispersed steel slag particles. In the early stage of curing, the shrinkage might be mitigated by the coordinated formation of ettringite and C-S-H gels. Besides, the reduced shrinkage leads to fewer stress loss of prestressed reinforcement in prefabricated structures. The findings indicate that the proposed concrete has a great potential to serve as the material for prefabricated structures or cast-in-situ concretes.

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Thermal Decomposition of Hydrated Alumina Cement (CAH10)

Cited by 51 publications

References 24 publications

Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

Characterisation of microstructural evolutions in refractory castables by in situ high temperature ESEM

On High-Strength Low-Shrinkage Iots-Based Concrete

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