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Ettringite

About: Ettringite is a research topic. Over the lifetime, 2702 publications have been published within this topic receiving 67056 citations. The topic is also known as: woodfordite.


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Journal ArticleDOI
TL;DR: In this article, the authors developed the limestone calcined clay (LC3) as a low-carbon treatment to immobilize waste ferronickel slag (FNS) containing heavy metals.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the solubility of oxyanion-substituted ettringite and monosulphate phases and solid solutions with SO 4 2 − and OH − have been synthesized.
Abstract: Cement has found wide usage in the stabilization of heavy-metal-containing wastes as cement minerals can substantially reduce heavy metal solubility as a result of precipitation, adsorption to the surfaces and incorporation. The solubility of some heavy metal cations is limited by the precipitation of hydroxides, while that of some oxyanions is limited by the formation of Ca salts. Only ions that are sufficiently soluble in basic media will be incorporated in or sorbed to hydrated cement minerals to a significant degree. Heavy metal cations may sorb quite strongly to calcium silicate hydrate (C-S-H). The cations diffuse into the C-S-H particles where they are probably sorbed to the silicate chains. Pure phases of oxyanion-substituted ettringite (3CaO·Al 2 O 3 ·3(CaSO 4 )·32H 2 O, an AFt phase) and monosulphate (3CaO·Al 2 O 3 ·CaSO 4 ·12H 2 O, an AFm phase) phases and solid solutions with SO 4 2 − and OH − have been synthesized. Some thermodynamic data are available for the pure phases. For most elements an approximate range of solubility has recently become known. However, it is not possible to predict solubility from the available data.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the same authors showed that the increase of solution temperature accelerates both magnesium attack and sulfate attack on the limestone filler cement mortar, and leads to more deleterious products including gypsum, ettringite and brucite formed on the surface of mortars after 1-year storage in sulfate solutions.
Abstract: Mortar prisms made with OPC cement plus 30% mass of limestone filler were stored in various sulfate solutions at different temperatures for periods of up to 1 year, the visual appearance was inspected at intervals, and the flexural and compressive strength development with immersion time was measured according to the Chinese standard GB/T17671-1999. Samples were selected from the surface of prisms after 1 year immersion and examined by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), laser-raman spectroscopy and scanning electron microscopy (SEM). The results show that MgSO4 solution is more aggressive than Na2SO4 solution, and Mg2+ ions reinforce the thaumasite sulfate attack on the limestone filler cement mortars. The increase of solution temperature accelerates both magnesium attack and sulfate attack on the limestone filler cement mortar, and leads to more deleterious products including gypsum, ettringite and brucite formed on the surface of mortars after 1 year storage in sulfate solutions. Thaumasite forms in the mortars containing limestone filler after exposure to sulfate solutions at both 5 °C and 20 °C. It reveals that the thaumasite form of sulfate attack is not limited to low-temperature conditions.

22 citations

DOI
01 Sep 2003
TL;DR: In this article, the authors demonstrate that ettringite is a preferred phase for the adsorption of polycondensate or polycarboxylate based superplasticizers, whereas polyCondensate and polycar boxylate practically show no signs of adsorbing.
Abstract: Superplasticizers typically work within the first 2 hours of cement hydration. Therefore, early hydration products have to be studied to investigate their mode of action. The experiments in this paper demonstrate that ettringite is a preferred phase for the adsorption of polycondensate or polycarboxylate based superplasticizers, whereas polycondensate amd polycarboxylate practically show no signs of adsorption. For polycarboxylate adsorption, time of addition to ettringite is not important whereas polycondensates adsorb much less when addition is delayed. Adsorption does not seem to occur and therefore cannot explain the different behavior of polycondensates. The presence of superplasticizers during ettringite formation reduces the crystal size of ettringite. The effect is particularly strong for polycondensate superplasticizers. There was no influence on ettringite morphology or quantity formed found.

22 citations

Journal ArticleDOI
TL;DR: In this article, a mixture of CaO, amorphous SiO2 and kaolinite was treated in suspension under hydrothermal conditions at temperatures of 80-200 °C.
Abstract: Mixtures of CaO, amorphous SiO2 and kaolinite in the presence or absence of SO 4 2− ions (added as CaSO4·2H2O) were treated in suspension under hydrothermal conditions at temperatures of 80–200 °C. Kaolinite was added to replace 3 and 10% of the total weight of the dry mix with the overall CaO/SiO2 mole ratio being 0.83. The hydration products were investigated by XRD, IR spectroscopy and DTA techniques in order to elucidate their phase compositions. The results indicate that the presence of SO 4 2− ions leads to a marked increase in the reaction rate at all temperatures investigated. In the C-S-A system, the detected hydration products are calcium silicate hydrate which is then transformed into 1.13 nm aluminium-substituted tobermorite and α-C2SH by increasing the autoclaving temperature. In the C-S-A-C¯s system the hydrated products are calcium silicate hydrate, ettringite and monosulpho-alumirtate. On increasing the hydrothermal temperature they decompose, recrystallize and 1.13 nm aluminium-substituted tobermorite, α-C2SH and anhydrite II are formed. In both systems the excess Al2O3 appeared as a hydrogarnet phase, C3ASH4.

22 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023244
2022439
2021175
2020161
2019166
2018143