Formation of ettringite in Portland cement/calcium aluminate cement/calcium sulfate ternary system hydrates at lower temperatures

Xu, Linglin; Wang, Peiming; Zhang, Guofang

doi:10.1016/j.conbuildmat.2011.12.078

Cited by 103 publications

(50 citation statements)

References 15 publications

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“…2 Among these 3 types of sulfate attacks, ettringite is the most widely investigated one. [4][5][6][7][8][9] In fact, the ettringite is enthusiastically studied by researchers not only because it is the main sulfate attack products but also because it is the main secondary hydration products of Portland cement, which contributes to the primary strength of hardened cement at an early stage. In contrast with ettringite, researches on thaumasite are much limited.…”

Section: Introductionmentioning

confidence: 99%

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

San

Tao

et al. 2018

J Am Ceram Soc

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Ettringite and thaumasite are 2 of the relevant secondary products in portland cement minerals. They are rare crystals with high water content. Two density functional theory based ab initio packages VASP and the OLCAO were used for exploring the geometry structure, electronic, and mechanical properties of ettringite and thaumasite. The calculations focus on the comparison of their structures and properties to gain insights that can reveal the minute difference in properties due to differences in their structure, composition and water content. Detailed analysis of interatomic bonding shows the similarities and subtle difference between them even though thaumasite has the Si tetrahedron as the backbone unit in contrast to ettringite with Al‐columns and no Si atoms. Moreover, thaumasite has strong C–O bonds that are absent in ettringite, and ettringite has far more water molecules with a substantial contribution from the hydrogen bonding. It is shown that the role played by relatively strong S–O bonds in both crystals has a large impact on the hydration in these crystals. On the basis of calculated total bond order density, it is concluded that thaumasite is slightly more cohesive than ettringite consistent with the calculated mechanical properties. The detailed comparative results for these 2 important minerals we obtained in this paper, many of them for the first time, will pave the way to understanding the structure and electronic structure origin of other more complex cement crystals.

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Section: Introductionmentioning

confidence: 99%

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

San

Tao

et al. 2018

J Am Ceram Soc

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“…are experienced with low temperature, especially negative temperature (<0 ∘ C) during initial hydration stage, cement hydration will be greatly affected [9][10][11]. In this case, the hydrated products, phase conversion, for example, from ettringite (AFt) to monosulfate (AFm), and pores solution will be affected by low temperatures [5,12]. In some limited conditions, the matrix would be even damaged.…”

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, the matrix of cement binder acts a greatly important role in Portland cement-based composites (i.e., pastes, mortars, concrete, stabilized stones, and treated soils). The performance of hardened Portland cement (e.g., mechanical behavior, and durability) is linked tightly with early age chemical hydration and hardening, while the relationships between hydration processes, hydrates produced, microstructures, and mechanical behaviors have been proved in previous studies [2][3][4][5]. In service life of infrastructures, cement-based materials have to be faced with severe environmental conditions, such as super-low temperatures [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Portland Cement Hydration Behavior at Low Temperatures: Views from Calculation and Experimental Study

Liu

Jiao

Sha

et al. 2017

Advances in Materials Science and Engineering

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Environmental condition affects the property of construction materials. This study gives an initial understanding of Portland cement hydration under low temperatures from the views of laboratory experiments (including electrical resistivity, degree of hydration (DoH), and maturity) as well as thermodynamic calculation. The hydrates of Portland cement at the given period were detected with X-ray diffraction (XRD), and their microstructure was observed by scanning electron microscope (SEM). Experiment result (i.e., DoH and electrical resistivity) indicated that the hydration of Portland cement was delayed by low temperature without hydration stopping at −5 ∘ C. Based on a basic kinetics model, the thermodynamic calculation predicted that the final hydrate differs in dependence on environmental temperatures. The mechanical behavior trend of Portland cement paste affected by low temperatures potentially is linked to the appearing of aluminate compounds and reduction of portlandite.

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“…Despite the large number of studies that have investigated either the use of ettringite in waste water treatment [12-16, 23-25, 36, 37] or its effect on the physical and chemical behavior of various types of cement [10,11,22,26,[38][39][40][41], as well as works dedicated to the structural characterization of this material [4-9, 18, 20, 27-29, 42], only a few studies investigating the thermal decomposition of ettringite exist in the literature [21,[43][44][45]. Therefore, the first aim of the present work is to characterize the ettringite decomposition products by applying the techniques of X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetry (TG/DTA), and scanning electron microscopy (SEM).…”

Section: Introductionmentioning

confidence: 99%

Kinetic and thermal decomposition of ettringite synthesized from aqueous solutions

Guimarães

Oliveira

Leão

2016

J Therm Anal Calorim

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The kinetics of the thermal decomposition of a synthetic ettringite sample was studied between 298 and 820 K in an inert atmosphere for the present work. The ettringite and its thermal decomposition products were characterized using X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. Four endothermic events were observed with thermogravimetry curves, the maxima of which occurred at 366, 397, 537, and 641 K. All events were associated with the loss of water molecules with different degrees of interaction within the ettringite structure. Chemical equations for each decomposition step were proposed based on the percentages of mass loss observed. In addition, for the first time, the activation energies of each ettringite decomposition events were determined by the isoconversional methods of Ozawa-Flynn-Wall, Friedman, and Kissinger-AkahiraSunose. The modeling revealed that the activation energy varied from *50 kJ mol -1 , characteristic of mass transfer control steps, to *150 kJ mol -1 , which is typical of chemical control, as the temperature increased and the ettringite structure lost water. A total of 32 mol of water was released equivalent to 43.1 % of the initial sample mass.

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Formation of ettringite in Portland cement/calcium aluminate cement/calcium sulfate ternary system hydrates at lower temperatures

Cited by 103 publications

References 15 publications

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

Portland Cement Hydration Behavior at Low Temperatures: Views from Calculation and Experimental Study

Kinetic and thermal decomposition of ettringite synthesized from aqueous solutions

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