Hydration of β-dicalcium silicate at high temperatures under hydrothermal conditions

Yanagisawa, Kazumichi; Hu, Xiulan; Onda, Ayumu; Kajiyoshi, Koji

doi:10.1016/j.cemconres.2005.12.009

Cited by 46 publications

(15 citation statements)

References 19 publications

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“…Compositional changes in the silicate matrix due to the presence of H 2 O during the hydration/dehydration tests at 450/550ºC were observed by XRD. These changes are consistent with the hydration of Ca 2 SiO 4 to form different hydrated silicates (Garbev et al 2014;Mitsuda et al 1985;Roßkopf et al 2015;Speakman et al 1967;Yanagisawa et al 2006), being Ca 5 (SiO 4 ) 2 (OH) 2 the main compound identified in our samples (Criado et al 2015). Although these hydrated silicates only represent a small fraction of the total amount of silicates present in the composite material, the formation of these hydrates could play a role in the deterioration of the mechanical properties over cycling.…”

Section: Observations On the Decay Of Crushing Strengthsupporting

confidence: 90%

Enhancement of a CaO/Ca(OH)2 based material for thermochemical energy storage

2016

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The application of hydration/dehydration reactions of CaO/Ca(OH) 2 to thermochemical energy storage systems can be facilitated by the development of Ca-based materials with improved mechanical properties when compared to the natural Ca-precursor, while maintaining good chemical activity. For this purpose, we are developing composite materials for fluidized bed or fixed bed applications synthesized using sodium silicate to bind fine CaO/Ca(OH) 2 particles. In this work, the mechanism of decay in the mechanical properties of the resulting CaO/Ca-silicates composites over hundreds of hydration/dehydration cycles has been investigated. Based on the observed mechanism, improvements to the method of synthesis of the materials have been introduced, in order to retain the original carbonate grain volumes, which are larger than those of the equimolar quantity of the expanding Ca(OH) 2 during hydration. A noticeable improvement in the mechanical stability of the resulting pellets was observed when the material was exposed to temperatures of around 880ºC in pure CO 2 before calcination in order to avoid the decomposition of CaCO 3 during the formation of the hard Ca-silicates that provide mechanical strength to the composite. Further gains in mechanical stability 2 were achieved by avoiding the complete hydration of the CaO grains in the composites. These results confirm the primary role of Ca(OH) 2 anisotropic expansion as the main cause of the reduction in crushing strength of the pellets. It can be concluded that the formation of calcium silicates as binders of CaO rich grains is a promising route for the development Ca-based composite materials. However, more effort is still needed to overcome the decay in performance observed after several hundreds of cycles.

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Section: Observations On the Decay Of Crushing Strengthsupporting

confidence: 90%

Enhancement of a CaO/Ca(OH)2 based material for thermochemical energy storage

2016

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“…This phase was formed from β-dicalcium silicate, the most important component of Portland cement, reacting with H 2 O under hydrothermal conditions. The γ-dicalcium silicate hydrate decomposed to form reinhardbraunsite and kilchoanite as the reaction proceeded, which is consistent with the kilchoanite trace in the same sample 43S1 [35]. The kilchoanite phase has been frequently encountered in the evaluation of cement paste with the addition of coarse silica flour at elevated temperatures [20].…”

Section: Mineral Compositionsupporting

confidence: 74%

Influence of the Particle Size Distribution of Silica Flour on the Mechanical and Microstructural Properties of Oil Well Cement Paste Exposed to HTHP Conditions

Xie¹

2019

Ceramics - Silikaty

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Silica flour is used to mitigate the strength retrogression and microstructure degradation problems of oil well cement paste in high temperature wells. This study investigates the effects of the particle size distribution of silica flour on the thermal stability of cement paste. After 7 days of hydrothermal curing at 80 °C, the cement paste was exposed to further aging for 7 or 28 days under high temperature and high pressure (HTHP) conditions in a sealed chamber at 260 °C (500 °F) and 21 MPa (2900 psi). The results show that 43% silica flour by weight of cement (BWOC) mitigates the strength degradation of silica-stabilized Portland cement (SSPC), and course silica flour (63.13 and 48.25 µm) maintains the strength stability of SSPC better than fine silica flour (3.25 µm). The transformation of C-S-H gel to xonotlite in SSPC was influenced by the silica particle size. The relatively fine silica flour (d 50 = 3.25 µm) accelerates the consumption of calcium hydroxide during the pozzolanic reaction, resulting in a poorer strength stability of SSPC than the courser silica flour (d 50 = 63.13 and 48.25 µm). The silica flour with an average particle size of 48.25 µm is more conducive to crystallization of xonotlite on the crystal plane corresponding to a diffraction angle of 25.5° than the other size silica flour.

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“…In a previous manuscript, we demonstrated that the first stage of dehydration of α‐C 2 SH is connected with the formation of Ca 6 [Si 2 O 7 ][SiO 4 ](OH) 2 , a compound known as the natural mineral dellaite . Up to that investigation, dellaite formation had been observed only in hydrothermal syntheses at elevated temperature and pressure . In addition, formation of dellaite from α‐C 2 SH as a starting material under hydrothermal conditions has already been observed at temperatures about 350°C .…”

Section: Introductionmentioning

confidence: 99%

A Modular Concept of Crystal Structure Applied to the Thermal Transformation of α‐C₂SH

2014

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A single crystal of a-Ca 2 [HSiO 4 ](OH) (a-C 2 SH) was repeatedly imaged at room temperature with synchrotron mid-infrared microscopy after heating to 310°C, 340°C, 370°C, and 400°C respectively. The mechanisms of the observed phase transformations are discussed on the basis of a modular concept of the crystal structures. All images show domains of dellaite, Ca 6 [Si 2 O 7 ][SiO 4 ](OH) 2 , which are predominantly formed in the core of the crystal. In the crystal rim area a-C 2 SH persists in higher abundance. The mechanism of the phase transformation of a-C 2 SH into dellaite includes the following: (1) O. We suggest that reaction (1) cannot be completed at ambient pressure. Thus in the regions close to the rim of the crystals we expect the formation of x-C 2 S, which starts along the crystal edges according to Ca 2 [HSiO 4 ](OH) ? Ca 2 SiO 4 + H 2 O. Based on a modular concept, a structural relationship between a-C 2 SH, killalaite, dellaite, and x-C 2 S has been established. Similarities and differences in the thermal behavior of a-C 2 SH and afwillite have been highlighted.

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Hydration of β-dicalcium silicate at high temperatures under hydrothermal conditions

Cited by 46 publications

References 19 publications

Enhancement of a CaO/Ca(OH)2 based material for thermochemical energy storage

Enhancement of a CaO/Ca(OH)2 based material for thermochemical energy storage

Influence of the Particle Size Distribution of Silica Flour on the Mechanical and Microstructural Properties of Oil Well Cement Paste Exposed to HTHP Conditions

A Modular Concept of Crystal Structure Applied to the Thermal Transformation of α‐C₂SH

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Hydration of β-dicalcium silicate at high temperatures under hydrothermal conditions

Cited by 46 publications

References 19 publications

Enhancement of a CaO/Ca(OH)2 based material for thermochemical energy storage

Enhancement of a CaO/Ca(OH)2 based material for thermochemical energy storage

Influence of the Particle Size Distribution of Silica Flour on the Mechanical and Microstructural Properties of Oil Well Cement Paste Exposed to HTHP Conditions

A Modular Concept of Crystal Structure Applied to the Thermal Transformation of α‐C2SH

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A Modular Concept of Crystal Structure Applied to the Thermal Transformation of α‐C₂SH