Zum Aufbau schlecht geordneter Calciumhydrogensilicate. I. Bildung und Eigenschaften einer schlecht geordneten Calciumhydrogendisilicatphase

Abstract

Durch Fällungsreaktion aus Natriumsilicatlösungen mit Calciumsalzen entstehen bei 0°C schlecht geordnete Calciumhydrogensilicate, deren Anionenaufbau primär dem des Natriumsilicates in der Lösung entspricht. Sie sind aber nicht stabil und werden in der Mutterlauge bei 0°C in Disilicat mit einer Zusammensetzung von 1,1–1,5 CaO/SiO2 umgewandelt, wenn die Konzentration an Ca(OH)2 mehr als 0,8 g/l beträgt. Nach Trocknung der thermisch sehr instabilen Bodenkörper bei–10°C kann die Disilicatphase isoliert werden. Ein Strukturvorschlag für diese Phase wird vorgestellt.

Cell Dimensions and Composition of Nanocrystalline Calcium Silicate Hydrate Solid Solutions. Part 2: X‐Ray and Thermogravimetry Study

“…Given that TG analysis revealed an increase in water content with increasing C/S ratio (Table I), the decrease in d ‐spacing upon irradiation may be attributed to loss of H 2 O, which is coordinated to Ca in the interlayer. The absence of any shrinkage in the sample with C/S=2/3 supports the model of Stade and Wieker, 2 with no Ca in the interlayer.…”

Surface carbonation of synthetic C-S-H samples: A comparison between fresh and aged C-S-H using X-ray photoelectron spectroscopy

“…The presence of structural features readily susceptible to decalcification indicate considerable defects within the tobermorite-like structure. In this respect, the mechanochemically prepared synthetic C-S-H phases used in this study may be considered to possess defect-tobermorite structures, similar to the model suggested by Stade and Wieker [20] and Cong and Kirkpatrick [21]. It is entirely reasonable to assume that mechanochemical synthesis of C-S-H phases yields tobermorite-like structures given Saito's use of this method to produce tobermorite [27].…”

“…Fujii and Kondo [19] initially considered C-S-H as a solid solution between tobermorite and portlandite. This was elaborated by Stade and Wieker [20] and Cong and Kirkpatrick [21], with the defect-tobermorite model, whereby variations in C/S ratio could be accommodated by defects in the tobermorite structure. The precise structure of C-S-H is system dependent [22], but a combination of the tobermorite-portlandite model and the tobermorite-jennite model adequately describes many systems, with the former being preferred in synthetic systems, and the latter in 'real' cement pastes.…”

Structural Features of C–S–H(I) and Its Carbonation in Air—A Raman Spectroscopic Study. Part I: Fresh Phases

“…Another possible contributor to the Raman scattering in the 1040–1200 cm −1 region could be hydroxylated tetrahedra in the silicate chains, whose presence has been proved feasible by Stade and Wieker 30 . In other words, the O non atoms participating in Si–O non –Ca linkages could be partially protonated, especially in samples of C–S–H(I) with a low C/S ratio 29 .…”

“…XRD patterns of C–S–H(I) resemble those of 14 Å tobermorite, Ca 5 [H 2 Si 6 O 18 ]·8H 2 O, showing reflections assigned primarily to ordering in the xy plane (with additional ordering in the z direction) via a basal reflection in the range 13–11 Å, which corresponds to the mean layer thickness 29 . Stade and Wieker 30 proposed a model for C–S–H(I) based on the tobermorite structure using “tobermorite slabs” as the principal building units. Single “tobermorite slabs,” comprising a calcium–polyhedral layer with silicate chains attached on both sides, are linked together via additional calcium atoms and/or water molecules.…”