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1.
SALLY A. RODGER GEOFFREY W. GROVES NIGEL J. CLAYDEN CHRISTOPHER M. DOBSON 《Journal of the American Ceramic Society》1988,71(2):91-96
The use of cross-polarization (CP) NMR in conjunction with magic angle sample spinning (MASS) to examine the hydration reaction of tricalcium silicate (C3 S) is described. In particular the very early stages of the reaction both with and without admixtures has been studied as well as the hydration in a ball mill. The combination of CP and non-CP 29 Si NMR permits the distinction between silicate units associated with protons, i.e., in hydrated material, and those in anhydrous material. It has been found that in paste hydration there is steady formation of a small amount of hydrated monomeric silicate units during the induction period. In ball mill hydration the formation of the crystalline calcium silicate hydrate, afwillite, which contains only hydrated monomeric silicate species, can be monitored. These results are interpreted in terms of possible mechanisms for C3 S hydration. 相似文献
2.
This paper investigated the hydration process of tricalcium silicate (C3S) in which a small amount of vinyltriethoxysilane (VTES) was added by using the techniques of 1H NMR, 29Si MAS-NMR and XRD. In comparison with the hydration process of C3S without adding any additives, not only the average molecular weight of hydrated calcium silicate in C3S paste, but also the ordering of the silicon nuclei in it increased. This indicates that the VTES has joined effectively into the real hydration process of C3S. These results imply some possible reasons why the intrinsic properties of low porosity hardened cement paste (HCP) in which a small amount of VTES was added could be improved. Besides, it has been found that in early stage hydration of C3S with or without VTES, Ca(OH)2 crystal in the paste appears earlier than Q1 which shows that in the first several hours of hydration, there only exists Si(OH)4 and other basic salts and no dimer and polymer of silicate anion when Ca(OH)2 crystal begins to form. 相似文献
3.
Characterization of C-S-H from Highly Reactive β-Dicalcium Silicate Prepared from Hillebrandite 总被引:1,自引:1,他引:0
Yoshihiko Okada Hideki Ishida Kaori Sasaki J. Francis Young Takeshi Mitsuda 《Journal of the American Ceramic Society》1994,77(5):1313-1318
β-dicalcium silicate synthesized by thermal dissociation of hydrothermally prepared hillebrandite (Ca2 (SiO3 )(OH)2 ) exhibits extremely high hydration activity. Characterization of the hydrates obtained and investigation of the hydration mechanism was carried out with the aid of trimethylsilylation analysis, 29 Si magic angle spinning nuclear magnetic resonance, transmission electron microscopy selected area electron diffraction, and XRD. The silicate anion structure of C-S-H consisted mainly of a dimer and a single-chain polymer. Polymerization advances with increasing curing temperature and curing time. The C-S-H has an oriented fibrous structure and exhibits a 0.73-nm dreierketten in the longitudinal direction. On heating, the C-S-H dissociates to form β-C2 S. The temperature at which βC2 S begins to form decreases with increasing chain length of the C-S-H or as the Ca/Si ratio becomes higher. The high activity of β-C2 S is due to its large specific surface area and the fact that the hydration is chemical-reaction-rate-controlled until its completion. As a result, the hydration progresses in situ and C-S-H with a high Ca/Si ratio is formed. 相似文献
4.
Nicolas Lequeux Alain Morau Samuel Philippot Philippe Boch 《Journal of the American Ceramic Society》1999,82(5):1299-1306
5.
Adrian R. Brough Christopher M. Dobson Ian G. Richardson Geoffrey W. Groves 《Journal of the American Ceramic Society》1994,77(2):593-596
Selective isotopic enrichment of SiO2 with 29 Si in a mixture with tricalcium silicate (C3 S) has allowed the Si from this phase to be effectively labeled during the course of the hydration reaction, thus isolating its contribution to the reaction. A double Q2 signal has been observed in 29 SI solid-state MAS NMR spectroscopy of C-S-H gels of relatively low Ca/Si ratio, prepared by hydration or by carbonation of a C3 S paste. The origin of the weaker, downfield peak is discussed and tentatively attributed to bridging tetrahedra of a dreierkette silicate chain structure. 相似文献
6.
The effects of Al3+ , B3+ , P5+ , Fe3+ , S6+ , and K+ ions on the stability of the β-phase and its hydration rate were studied in reactive dicalcium silicate (C2 S, Ca2 SiO4 ) synthesized using the Pechini process. In particular, the dependences of the phase stability and degree of hydration on the calcination temperature (i.e., particle size) and the concentration of the stabilizing ions were investigated. The phase evolution in doped C2 S was determined using XRD, and the degree of hydration was estimated by the peak intensity ratio of the hydrates to the nonhydrates in 29 Si MAS NMR spectra. The stabilizing ability of the ions varied significantly, and the B3+ ions were quite effective in stabilizing the β-phase over a wide range of doping concentrations. The hydration results indicated that differently stabilized β-C2 S hydrated at different rates, and Al3+ - and B3+ -doped C2 S exhibited increased degree of hydration for all doping concentration ranges investigated. The effect of the doping concentration on degree of hydration was strongly dependent on the stabilizing ions. 相似文献
7.
Reactive dicalcium silicate (Ca2 SiO4 ) has been synthesized by the Pechini process, and hydration kinetics studied. With increasing calcination temperature, the amorphous product first crystallizes to α'L -phase and subsequently to the ß- and γ-phases. The specific surface area, ranging from 40 to 1 m2 /g, strongly depends on the calcination temperature of 700°-1200°C for 1 h. Samples with a high surface area have a high water demand; a water/cement ratio >2.0 is required to produce formable pastes in some instances. Hydration kinetics are determined by XRD, 29 Si magic-angle spinning nuclear magnetic resonance (MAS NMR), and differential scanning calorimetry/thermogravimetry (DSG/TG). The hydration rate depends only on the surface area, not on the polymorph. Complete hydration occurs in as early as 7 d. Very little calcium hydroxide (Ca(OH)2 ) is formed in the most reactive specimens (calcined at 700° and 800°C), which indicates the Ca/Si ratio in C-S-H gels is ∼2.0, but more Ca(OH)2 forms from samples calcined at higher temperature. The silicate structure of the hydrated Ca2 SiO4 pastes is investigated using 29 Si MAS NMR spectroscopy and trimethylsilylation analysis. 相似文献
8.
Hideki Ishida Kaori Sasaki Takeshi Mitsuda 《Journal of the American Ceramic Society》1992,75(2):353-358
The hydration behavior at 25°C of β-dicalcium silicate synthesized from hillebrandite (Ca2 ,(SiO3 )(OH)2 ) at 600°C was studied over a period of 224 d. The hydration rate of the β-dicalcium silicate having fibrous crystals with specific surface area of 7 m2 /g is extremely rapid. For water/solids ratios of 0.5 and 1.0, the hydration reaction is completed in 28 and 14 d, respectively. The hydrate contains almost no Ca(OH)2 , and its Ca/Si ratio is close to 2. SEM observations indicate that the hydrate forms an outer shell on the surface of β-dicalcium silicate and grows inwards. The silicate anion structure is considered to consist of dimers and single-chain structures from 29 Si MAS NMR. Variations of physical properties of press-formed bodies have also been discussed. 相似文献
9.
Kaori Sasaki Tsuguya Masuda Hideki Ishida Takeshi Mitsuda 《Journal of the American Ceramic Society》1997,80(2):472-476
An amorphous, C-S-H-like phase with Ca/Si = 2 was synthesized from amorphous precipitated silica, calcium oxide, and water by mechanochemical treatment using a vibration mill at room temperature. The product was studied by XRD, 29 Si MASNMR, TEM, analytical TEM, and TGA-DTA. After 14 h of treatment, the starting materials react to form an amorphous phase (C-S-H-like phase). The XRD pattern of C-S-H-like phase resembles the C-S-H formed hydrothermally or by cement hydration except it has no reflection at 0.182 nm. The 29 Si NMR results revealed a silicate anion structure of C-S-H-like phase consisting mainly of a mixture of a monomer and a dimer. On heating, the C-S-H-like phase decomposed into β-dicalcium silicate below 1000°C. 相似文献
10.
Wang-Hong Yang R. James Kirkpatrick Gary Turner 《Journal of the American Ceramic Society》1986,69(10):222-C
11.
Paul J. Schilling Leslie G. Butler Amitava Roy Harvill C. Eaton 《Journal of the American Ceramic Society》1994,77(9):2363-2368
b29 Si and 27 Al MAS-NMR were performed on NaOH-activated blast-furnace slag to better characterize the amorphous and poorly crystalline phases which occur in this system. The unreacted glass has a mainly dimeric silicate structure represented by a broad 29 Si peak (FWHM = 15 ppm) centered at –74.5 ppm [ Q 1 ], with aluminum present exclusively in tetrahedral coordination. Upon reaction with 5M NaOH ( w/s = 0.4), three new 29 Si peaks with widths of ca. 2 ppm are formed at -78.5 Q 1 , –81.4 [ Q 2 (1Al)J, and -84.3 [ Q 2 ]. Relative peak areas indicate a mostly dimeric silicate structure for the tobermorite-like C─S─H layers, with roughly a third of the bridging sites occupied by aluminum, and less than 10% by silicon. In addition to the tetrahedrally coordinated aluminum substituted in the C─S─H structure, 27 Al MAS-NMR reveals the presence of aluminum in octahedral sites, which is attributed to the aluminate phase (C,M)4 AH13 . 29 Si results indicate rapid initial consumption of the glass, with roughly a third of the glass reacting within the first day and another third consumed over the following 27 days. 相似文献
12.
Heather M. Dyson Ian G. Richardson Adrian R. Brough 《Journal of the American Ceramic Society》2007,90(2):598-602
Quantification of the C–S–H hydrates and anhydrous material in plain and blended cement systems can be performed by deconvolution of 29 Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectra. NMR data are reliable for simple cement systems, but with the incorporation of supplementary cementitious materials, quantification is often uncertain. For example, the overlap of peaks from slag cement and C–S–H in 29 Si MAS NMR spectra causes problems with deconvolution. A novel method was developed to address these difficulties. 29 Si MAS NMR was combined with a selective dissolution method. The hydrate peaks in slag blends can now be quantified without interference from the slag peak. This new method enables the silica remaining in unreacted slag to be estimated, thus allowing the degree of slag hydration to be quantified. Hydrate Al/Si ratios correlate well with data from analytical transmission electron microscopy (TEM). Analysis of the dissolution residues by TEM and 29 Si MAS NMR indicates that they consist of a mixture of unreacted slag, a hydrotalcite-type phase, and small amounts of aluminosilicate gel. The origin of the aluminosilicate gel needs further investigation. 相似文献
13.
Jian Jiao Wei Wang Bogdan Sulikowski Jens Weitkamp Michael Hunger 《Microporous and mesoporous materials》2006,90(1-3):246-250
Solid-state NMR characterization of zeolite catalysts in the hydrated state is often accompanied by an uncontrolled hydrolysis of the framework. In the present work it is demonstrated that the limitations occurring for 29Si and 27Al MAS NMR spectroscopy of non-hydrated zeolites Y, such as strong decrease of resolution and significant line broadening, can be overcome by loading these materials with ammonia. In the 29Si MAS NMR spectra of non-hydrated and ammonia-loaded zeolites Y, no dehydration-induced high-field shift of Si(nAl) signals (n = 3, 2, 1) occurs, which is generally responsible for the loss of resolution in the spectra of non-hydrated materials. The 27Al MAS NMR spectra of the non-hydrated and ammonia-loaded zeolites Y consist exclusively of signals of the tetrahedrally coordinated framework aluminum atoms with spectroscopic parameters similar to those of framework aluminum atoms in hydrated samples. The framework nSi/nAl ratios of the non-hydrated zeolites Y obtained by both 29Si and 27Al MAS NMR spectroscopy upon ammonia-loading agree well with each other. 相似文献
14.
Sabine Thomas Karin Meise-Gresch Werner Müller-Warmuth Ivan Odler 《Journal of the American Ceramic Society》1993,76(8):1998-2004
15.
A naturally occurring 1.4 nm tobermorite and a synthetic jennite were characterized by 27Al and 29Si magic angle spinning nuclear magnetic resonance (MASNMR) spectroscopy and their cation exchange properties were measured. 27Al MASNMR spectroscopy revealed that both the 1.4 nm tobermorite and synthetic jennite contained trace quantities of Al in tetrahedral coordination. The 1.4 nm tobermorite also contained octahedrally coordinated Al probably due to the presence of an aluminum compound as a trace impurity. The 29Si MASNMR spectrum of 1.4 nm tobermorite exhibited a strong resonance at −85.2 ppm and a small shoulder at −80 ppm which are attributed to chain middle groups (Q2) and end groups (disilicates) respectively. 29Si MASNMR spectroscopy of the synthetic jennite showed a strong resonance at −85.7 ppm and a moderately strong resonance at −81.4 ppm which correspond to single chains and end groups respectively. Jennite showed a considerably larger quantity of end groups than the 1.4 nm tobermorite. The unsubstituted 1.4 nm tobermorite and synthetic jennite exhibited only small cation exchange capacities. 相似文献
16.
Characterization of SAPO-11 and SAPO-31 synthesized from aqueous and non-aqueous media 总被引:5,自引:0,他引:5
Medium-pore SAPO-11 and SAPO-31 molecular sieves were synthesized from aqueous and non-aqueous (ethylene glycol) media. All the samples were characterized by XRD, SEM, N2 adsorption (BET analysis), TGA-DTA, pyridine-TPD, 27Al MAS-NMR, and 29Si MAS-NMR. The samples synthesized from non-aqueous medium possess higher acidity due to higher substitution of Si4+ at P5+ sites and less silica island formation, as evidenced from 29Si MAS-NMR spectra. It is possible to incorporate more silicon in the samples by synthesis in ethylene glycol medium. The SAPOs synthesized from non-aqueous medium show higher activity for the isomerization of m-xylene. 相似文献
17.
New and ordered 2D-hexagonal (p6mm) mesoporous aluminosilicates (CMI-11) have been synthesized in strongly alkaline media using aluminosilicate ester ((BusO)2-Al-O-Si-(OEt)3) as single-source molecular precursor and CTMABr as surfactant and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption and 27Al and 29Si MAS NMR spectroscopy. These mesoproous aluminosilicates exhibit a very low Si/Al ratio of 1.9 and highly thermal stable tetrahedral aluminum sites in the mesoporous walls. 27Al and 29Si MAS NMR spectroscopy indicates that the pore walls of CMI-11 are fully condensed with molecular homogeneity of Si–O–Al linkage. These materials are highly important in catalysis, in particular for the petroleum processing and the bulky molecules treatment. 相似文献
18.
Guokuang Sun Adrian R. Brough † J. Francis Young 《Journal of the American Ceramic Society》1999,82(11):3225-3230
19.
Urea bridged organic–inorganic hybrid mesoporous SiO2 materials (U-BSQMs) were synthesized through a sol–gel procedure by co-condensation of bis(triethoxysilyl propyl) urea (BSPU) under basic conditions using cetyltrimethylammonium bromide (CTAB) as organic template. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the mesoporous structure of the sample. Fourier-transform infrared spectroscopy (FT-IR), solid state CP-MAS NMR spectroscopy of 29Si (29Si CP-MAS NMR) and 13C (13C CP NMR) indicated that most of the Si–C bonds are unbroken during the synthesis process. The N2 adsorption–desorption results revealed that these hybrid mesoporous SiO2 materials have bimodal distribution of pores with pore diameters of 2.4 and 3.8 nm, respectively. Thermogravimetric analysis (TG) demonstrated that about 16% Si–C bonds have been broke during the synthesis progress. This kind of material is expected to find possible application in ion supporting, drug delivery and catalysis. 相似文献
20.
The retarding action of sugars on cement hydration 总被引:4,自引:0,他引:4
Sugars retard the hydration of Portland cement. The effectiveness of different sugars is compared from studies of solution analysis, calorimetry, calcium binding ability and alkaline stability. The best retarders, sucrose and raffinose, have a remarkable ability to solubilize cement constituents and in particular give rise to dramatic increases in the amount of silica in solution. However, 13C and 29Si N.M.R. do not reveal the existence of sucrose-silicate complexes. The retarding action of sugars is explained in terms of adsorption onto and poisoning of hydrate surfaces. 相似文献