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1.
Beta C2 S was hydrated at room temperature with and without added CaCl2 or C2 H5 OH by methods previously studied for the hydration of C3 S, i.e. paste, bottle, and ball-mill hydration. The amount of reacted β-C2 S, the Ca(OH)2 concentration in the liquid phase, the CaO/SiO2 molar ratio, and the specific surface area of the hydrate were investigated. A topochemical reaction occurs between water and β-C2 S, resulting in the appearance of solid Ca(OH)2 and a hydrated silicate with a CaO/SiO2 molar ratio of ≃1. As the liquid phase becomes richer in Ca(OH)2 , the first hydrate transforms to one with a higher CaO/SiO2 ratio. Addition of CaCl2 increases the reaction rate and the surface area of the hydrate but to a much lesser extent than in the hydration of C3 S, whereas C2 H6 OH strongly depresses the hydration rate of β-C2 S, as observed for C3 S hydration. 相似文献
2.
The Pore Structure of Hydrated Cementitious Compounds of Different Chemical Composition 总被引:1,自引:0,他引:1
ARNON BENTUR 《Journal of the American Ceramic Society》1980,63(7-8):381-386
The pore structure ofβ-C2 S, C3 S, and portland cement pastes was investigated using mercury porosimetry and H2 O and N2 adsorption. The β-C2 S had more total macro- and mesoporosities than C3 S and portland cement pastes of a similar degree of hydration. C3 S and portland cement pastes had similar total porosities but differed in the porosity size distribution. In the mesopore range, the various test methods gave different results. These differences are discussed on the basis of the various models proposed for cement paste. It is shown that shrinkage could be correlated with the volume of pores <0.03 μm, but not with total porosity. 相似文献
3.
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
4.
Calcium aluminosulfate (Ca4 Al6 O16 S or C4 A3 ̄) was prepared by direct synthesis from calcium and aluminum nitrates, and aluminum sulfate. CaAl4 O7 (CA2 ) formed as an intermediate at 900°C, and C4 A3 ̄ was the main phase after calcination at 1100°C. The specific surface areas after calcination at 1100° and 1300°C were ∼2.5 and 1 m2 /g, respectively. Hydration was investigated using XRD, DSC, SEM, conduction calorimetry, and solid-state 27 Al MAS-NMR spectroscopy. Calorimetry showed that the induction period was longer than that of a sample prepared using conventional solid-state sintering, and this was attributed to the formation of amorphous coatings. Crystalline hydration products, principally calcium monoaluminosulfate hydrate and aluminum hydroxide, appeared subsequently. Although the induction period was very long, complete hydration occurred as early as 3 d in the sample calcined at 1100°C and was 91% complete in the sample calcined at 1300°C. 相似文献
5.
Hideki Ishida Satoru Yamazaki Kaori Sasaki Yoshihiko Okada Takeshi Mitsuda 《Journal of the American Ceramic Society》1993,76(7):1707-1712
α-C2 SH can be synthesized by hydrothermal treatment of lime and silicic acid for 2 h at 200°C. When heated to 390–490°C, α-C2 SH dissociates through a two-step process to form an intermediate phase plus some γ-C2 S. This appears to be a new dicalcium silicate different from known dicalcium silicates—α, α'L , α'H , β, and γ phase—and is stable until around 900°C. At 920–960°C, all the phases are transformed to the α'L phase. The intermediate phase has high crystallinity and is stable at room temperature. 29 Si MAS NMR measurements indicate the possibility that it contains both protonated and unprotonated monosilicate anions. The intermediate phase that has passed through the α'phase at higher temperature yields β-C2 S on cooling. The intermediate phase is highly active, and completed its hydration in 1 day ( w/s = 1.0, 25°C). Among the crystalline calcium silicate hydrates with Ca/Si = 2.0, it is hillebrandite that yields β-C2 S at the lowest temperature. 相似文献
6.
Sung-Woo Choi Seong-Hyeon Hong Young Jin Kim 《Journal of the American Ceramic Society》2009,92(9):2025-2028
The green emitting Ca2 SiO4 :Eu2+ (C2 S:Eu) phosphors were synthesized by the polymeric precursor process (Pechini-type), and the effects of calcination temperature and europium (Eu) doping concentration on the luminescent properties were investigated. The crystalline β-C2 S was obtained in the calcination temperature of 1100°–1400°C, and Eu was reduced into Eu2+ by annealing in 5% H2 /N2 atmosphere. The obtained C2 S:Eu2+ phosphors exhibited a strong emission at 504 nm under the excitation of λexc =350 nm. The highest photoluminescence (PL) intensity was observed in the C2 S:Eu2+ phosphors either calcined at 1300°C or doped with 3 mol% Eu. The obtained PL properties were discussed in terms of crystal structure, particle size and shape, surface roughness, and effect of concentration quenching. 相似文献
7.
Hideki Ishida Kaori Sasaki Yoshihiko Okada Takeshi Mitsuda 《Journal of the American Ceramic Society》1992,75(9):2541-2546
The effect of curing temperature (40°, 60°, 80°C) on the hydration behavior of β-dicalcium silicate (β-C2 S) was investigated. The β-C2 S was obtained by decomposition of hillebrandite, Ca2 (SiO3 )(OH)2 , at 600°C, has a specific surface area of about 7 m2 /g, and is in the form of fibrous crystals. The dependence of the hydration reaction on temperature continues until the reaction is completed. The hydration is completed in 1 day at 80°C and in 14 days at 14°C. The hydration mechanism is different above and below 60°C, but at a given temperature, the reaction mechanism and the silicate anion structures of C-S-H do not change significantly from the initial to the late stages of the reaction. High curing temperature and long curing times after completion of reaction promote silicate polymerization. The Ca/Si ratio of C-S-H shows high values, being almost 2.0 above 60°C and 1.95 below 40°C. 相似文献
8.
GERARDO CHIOCCHIO MARIO COLLEPARDI RENATO TURRIZIANI 《Journal of the American Ceramic Society》1975,58(5-6):185-188
Hydrated calcium silicates containing Al3+] or Fe3+] were prepared by autoclaving C3 S and β-C2 S in the presence of C3 A or C2 F at 190°C. Al3+] and Fe3+] diffuse into the crystal lattice of α-C2 SH and C3 SH1.5 . Solid solutions containing Al3+] and Fe3+] were placed in contact at 25°C with sources of sulfates, either in aqueous stirred suspensions or as pastes. Al3+] and Fe3+] remain stable in the solid solution, inhibiting the formation of ettringite. This absence of ettringite can explain the resistance of autoclaved cement pastes and concretes to sulfate attack. 相似文献
9.
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
10.
R. L. BERGER ARNON BENTUR N. B. MILESTONE J. H. KUNG 《Journal of the American Ceramic Society》1979,62(7-8):358-362
The chemical and physical properties of C3 S, β-C2 S, a C3 S/C2 S blend, and portland cement pastes cured at 25°C were investigated. The H2 O specific surface areas of the calcium silicate samples follow a common linear relation when plotted against a CIS ratio. The β-C2 S had higher capillary porosity and N2 surface area, resulting from increased mesopore volume at the expense of micropores. All calcium silicate pastes had similar polysilicate content vs time curves, indicating an aging process which is not sensitive to the starting composition of the hydrating calcium silicate. The polysilicate content of portland cement was much lower than that of the corresponding calcium silicate pastes. Strength-capillary porosity relations for the various systems are discussed. 相似文献
11.
Reaction of Beta-Dicalcium Silicate and Tricalcium Silicate with Carbon Dioxide and Water Vapor 总被引:2,自引:0,他引:2
C. J. GOODBRAKE J. F. YOUNG R. L. BERGER 《Journal of the American Ceramic Society》1979,62(3-4):168-171
The carbonation-reaction kinetics of beta-dicalcium silicate (2CaO·SiO2 or β-C2 S) and tricalcium silicate (3CaO. SiO2 or C3 S) powders were determined as a function of material parameters and reaction conditions and an equation was developed which predicted the degree of reaction. The effect of relative humidity, partial pressure of CO2 , surface area, reaction temperature, and reaction time on the degree of reaction was determined. Carbonation followed a decreasing-volume, diffusion-controlled kinetic model. The activation energies for carbonation of β-C2 S and C3 S were 16.9 and 9.8 kcal/mol, respectively. Aragonite was the principal carbonate formed during the reaction and the rate of carbonate formation was coincident with depletion of the calcium silicates; C-S-H gel formation was minimal. 相似文献
12.
Laurent Bonafous Catherine Bessada Dominique Massiot Jean-Pierre Coutures Bruno Le Holland Pierre Colombet 《Journal of the American Ceramic Society》1995,78(10):2603-2608
The effect on β-C2 S of two stabilizing agents, calcium sulfate and alumina, has been investigated using high-resolution 29 Si solid state NMR spectroscopy. Syntheses were achieved via the gel route, wet or dry processes. Room-temperature NMR spectra characteristics were analyzed as a function of the sintering temperature. The incorporation of Al3+ and S6+ ions, which finds expression in a noticeable line broadening, is shown to be effective above 1200°C. The 29 Si chemical shift is unchanged upon doping, suggesting a mean SiO4 tetrahedra geometry identical to that in pure β-C2 S. General trends on the structure adopted by C2 S upon Al3+ and S6+ doping are also discussed. 相似文献
13.
The adsorption of calcium lignosulfonate and salicylic acid was studied on the hydration products of the four principal components of portland cement. To investigate the adsorption as a function of development of hydration product, the determinations were made after varying hydration times. The times allowed were from 5 min to 24 hr for tricalcium aluminate (C3 A) and tetracalcium aluminoferrite (C4 AF) and from 1 hr to 28 days for β-dicalcium silicate (β-C2 S) and tricalcium silicate (C3 S). Samples were characterized with respect to surface area and poresize distribution. The effect of gypsum on the adsorption was also investigated. The results indicate that the amounts of salicylic acid and calcium lignosulfonate adsorbed on the hydration products of C3 A, and of calcium 相似文献
14.
Yoshihiko Okada Kaori Sasaki Baiqian Zhong Hideki Ishida Takeshi Mitsuda 《Journal of the American Ceramic Society》1994,77(5):1319-1323
A mixture of CaO and silicic acid prepared with a Ca/Si ratio of 2.0 was hydrothermally synthesized at 80° to 200°C, and the thermal decomposition behavior of the products (C-S-H with Ca(OH)2 ) was analyzed using XRD, 29 Si MAS NMR, and the trimethylsililation method (TMS). It was found that the main silicate anion structure of C-S-H was a mixture of a dimer and a single-chain polymer (larger than Si5 O16 ) and that polymerization advanced with an increase of the synthesizing temperature. On heating, the products decomposed to form β-C2 S. It was found that the decomposition was gradual and that the-higher the temperature of hydrothermal synthesis, the lower was the temperature of the decomposition into β-C2 S. Although the decomposition proceeded to form a monomer (β-C2 S) from the polymer and dimer, this dimer was resistant to heat and did not decompose unless heated to above 400°C. 相似文献
15.
A. Cüneyt Tas 《Journal of the American Ceramic Society》1998,81(11):2853-2863
The binary compounds Ca3 Al2 O6 (C3 A), Ca12 Al14 O33 (C12 A7 ), CaAl2 O4 (CA), CaAl4 O7 (CA2 ), and CaAl12 O19 (CA6 ) in the CaO-Al2 O3 system have been synthesized as high-compound-purity ceramic powders by using the self-propagating combustion synthesis (SPCS) method. Materials characterization of the above-mentioned phases was performed via powder X-ray diffractometry (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The structural characterization of the C12 A7 phase has been performed via Rietveld analysis on the powdered XRD samples. It has hereby been shown that, by using this synthesis procedure, it should be possible to manufacture high-purity ceramic powders of CA, CA2 , and C12 A7 at 850°C, C3 A at 1050°C, and CA6 at 1200°C in a dry-air atmosphere. 相似文献
16.
Koichiro Fukuda Iwao Maki Suketoshi Ito Hideto Yoshida 《Journal of the American Ceramic Society》1995,78(12):3387-3389
A pseudobinary phase equilibrium diagram has been established for the P2 O5 -bearing Ca2 SiO4 -CaFe4 O7 system to confirm the occurrence of remelting reaction in α-Ca2 SiO4 solid solutions (C2 S(ss)). The reaction started at 1290°C immediately after the α-to-α'H transition and finished at 1145°C. The reaction products were made up of about 1 wt% of liquid and 99 wt% of solid α'H -C2 S(ss). The liquid exsolved at 1290°C was rich in Fe2 O3 , consisting of about 30 wt% of Ca2 SiO4 and 70 wt% of CaFe4 O7 . The liquid coexisting with α-C2 S(ss) precipitated new α'-phase crystals in association with the remelting reaction. 相似文献
17.
Marie-Noëlle de Noirfontaine Sandrine Tusseau-Nenez Marcel Signes-Frehel Gilles Gasecki Caroline Girod-Labianca 《Journal of the American Ceramic Society》2009,92(10):2337-2344
Alite is the major compound of anhydrous Portland cement: it is composed of tricalcium silicate Ca3 SiO5 (C3 S) modified in composition and crystal structure by ionic substitutions. Alite is also the main hydraulic phase of cement and the most important for subsequent strength development. Using raw meals (rich in Ca3 P2 O8 ) as alternative fuels in cement plants raises the question about the effect of phosphorus on C3 S and its consequences on reactivity with water. This paper deals with a systematic study of C3 S triclinic T1 polymorph doped with P2 O5 in the range 0–0.9 wt%. All the samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and electron-microprobe analysis. The appearance of a phase rich in phosphorus is shown. It displays a structure derivative of the α'H –Ca2 SiO4 polymorph, noted α'H –C2 S(P). As phosphorus content increases, C3 S is more and more decomposed into free lime and α'H –C2 S(P). The α'H phase was detected from 0.1 wt% P2 O5 and located at the interfaces of C3 S grains. Two identification keys are proposed in order to highlight the α'H –C2 S(P) phase: the XRD angular window at 2θCu =32.8°–33.2° and a smooth aspect on SEM micrographs. 相似文献
18.
Koichiro Fukuda Iwao Maki Suketoshi Ito Susumu Ikeda 《Journal of the American Ceramic Society》1996,79(10):2577-2581
A series of strontium-bearing dicalcium silicate (Ca2 Si04 solid solutions (C2 S( ss )), (Srχ Ca1-χ )2 SiO4 with 0.02 ≤χ≤ 0.10, was prepared and examined by powder X-ray diffrac-tometry. These crystals, heated in the stable-temperature region of the α phase and then quenched in water, were composed of the β phase, with χ≤ 0.08, and the α'L and β phases, with χ= 0.10. With increasing x, the unit-cell axes of the β phase expanded and the β angle became small with eventual increase in the unit-cell volume. The Rietveld analysis of the β-C2 S( ss ) with χ= 0.08 showed that the Sr2+ ions preferentially occupied the seven-coordinated site rather than the eight-coordinated site. This site preference, which was originally established in the parent α-phase structure, seemed to cause the systematic change in the cell dimensions. 相似文献
19.
Kaori Sasaki Hideki Ishida Yoshihiko Okada Takeshi Mitsuda 《Journal of the American Ceramic Society》1993,76(4):870-874
The hydration of β-C2 S prepared from hillebrandite [Ca2 (SiO3 )(OH)2 ] and having specific surface areas of 6.8, 5.5, and 3.1 m2 /g was investigated. Different specific areas were obtained by varying the dissociation temperature of hillebrandite. In addition, the hydration of β-C2 S synthesized from high-temperature solid-state reaction was also studied as a comparison. The specific surface area exerts a strong influence on the hydration rate, which increases as the surface area increases. The degree of influence changes with the reaction, becoming greater as hydration progresses. There is initially a linear relationship between specific area and the time required to complete a specific reaction. The specific surface area also affects the reaction mechanism. In the case of specific areas of 5.5 m2 /g or less, the reaction changes from a chemical reaction to a diffusion-controlled one, and the degree of reaction comes almost to a halt at 80% to 85%. The Ca/Si ratios of hydrate and the silicate anion structures were also investigated in this study. 相似文献
20.
Guokuang Sun Adrian R. Brough † J. Francis Young 《Journal of the American Ceramic Society》1999,82(11):3225-3230