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1.
J. F. YOUNG 《Journal of the American Ceramic Society》1969,52(1):44-47
The behavior of tricalcium silicate and related alites toward a lignosulfonate retarder (LSA) when tricalcium aluminate (C3 A) is added was studied by X-ray diffraction and by thermal analysis. In the absence of C3 A the hydration of the silicates is retarded indefinitely by LSA at the dosage used in this study. The retarding action of LSA was counteracted by the addition of 5% C3 A, apparently through preferential adsorption of the additive onto C3 A. Any calcium aluminate hydrates formed were detected by DTA. Their formation during the hydration of an alite of Jeffery's formulation confirmed that it does contain C3 A. 相似文献
2.
Early Hydration of Tricalcium Silicate 总被引:1,自引:0,他引:1
M. E. TADROS JAN SKALNY R. S. KALYONCU 《Journal of the American Ceramic Society》1976,59(7-8):344-347
The hydration of tricalcium silicate (C3 S) in the preacceleration stages was studied. The C3 S particles carry a positive charge during the early stages of hydration. Following a rapid hydrolysis of C3 S, calcium ions adsorbed on the Si-rich surface of C3 S particles, greatly reducing their further dissolution, thus initiating the induction period. The [Ca2+ ] and [OH- ] continue to increase at lower rates and, because Ca(OH)2 crystal growth is inhibited by silicate ions, become supersaturated with respect to Ca(OH)2 . When the supersaturation reaches a value of ∼1.5 to 2.0 times the saturation concentration, nuclei are formed, and rapid growth of Ca(OH)2 and C-S-H is initiated. These products act as sinks for the ions in solution, thus enhancing the further dissolution of C3 S. 相似文献
3.
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
4.
J. F. YOUNG 《Journal of the American Ceramic Society》1970,53(2):65-69
The paste hydration of tricalcium aluminate (C3 A) in the presence of organic compounds was investigated at several temperatures up to 75°C. The results confirm earlier hypotheses that the hexagonal calcium aluminate hydrates (principally C4 AH13 ) which are first formed create a protective barrier around the remaining C3 A and severely restrict further hydration. Above 30°C, conversion to C3 AH6 breaks down this barrier and causes rapid hydration of C3 A. Organic compounds retard the hydration of C3 A by inhibiting the conversion reaction. Experiments with synthetic C4 AH13 showed that organic molecules can form interlayer compounds, and it is considered that random sorption into the C3 AH13 structure restricts the transformation to C3 AH6 . Other aspects of C3 A hydration and of the reactivity of C4 AH13 are also discussed. 相似文献
5.
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
6.
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
7.
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
8.
Calcium Silicate Carbonation Products 总被引:2,自引:0,他引:2
Seishi Goto Kenzo Suenaga Takeshi Kado Minoru Fukuhara 《Journal of the American Ceramic Society》1995,78(11):2867-2872
calcium silicates such as C3 S, βT-C2 S, and γgM-C2 S † were carbonated under saturated humidity at room temperature. Carbonation products were examined by DT-TGA, gasphase mass spectroscopy, and XRD. Two types of carbonate were produced: one type, which was rather poorly crystallized, was decarbonated at a very low temperature, below 600°C; the other type was a crystalline phase such as calcite, aragonite, and/or vaterite which was decarbonated above 600°C. The data were compared to existing data for calcium carbonates and basic calcium carbonates. The results suggest that an amorphous calcium silicate hydrocarbonate was one of the carbonation products which formed during the hydration/carbonation reaction. 相似文献
9.
C. J. GOODBRAKE J. F. YOUNG R. L. BERGER 《Journal of the American Ceramic Society》1979,62(9-10):488-491
The carbonation of wetted powders of beta-dicalcium silicate (β·2CaO·SiO2 =β-C2 S) and tricalcium silicate (3CaO·SiO2 = C3 S) was studied as a function of reaction conditions. The water/solids ratio is an important parameter and there is an optimum value for each silicate. Relative humidity and the partial pressure of CO2 also strongly affect the reaction. The rate of carbonation can be conveniently represented by plotting the degree of carbonation against the logarithm of time. C-S-H and calcite are the initial reaction products. Subsequently, carbonation of the C-S-H produces silica gel, whereas aragonite may form if the system is allowed to dry out. 相似文献
10.
MERCEDES PÉREZ-MÉNDEZ G. W. GROVES JOSÉ FAYOS 《Journal of the American Ceramic Society》1986,69(9):670-673
There is evidence both by XRPD and by TEM electron diffraction of the presence of a new tricalcium silicate phase containing fluorine with triclinic cell parameters a = 2.32(7), b = 0.71(3), c = 1.28(3) nm, α= 106.5(3), β= 90(1), γ= 118(1)°. It is a superlattice of the rhombohedral C3 S, whose structure is probably deformed by the fluorine/oxygen substitution plus some calcium vacancies, the deformation being nevertheless smaller than that found in the triclinic polymorph of pure C3 S. Magnesium proves to have an effect additional to that observed for fluorine probably because it fixes the fluorine to the silicate lattice. 相似文献
11.
The formation of hydrates in dispersions of cubic tricalcium aluminate (C3 A)–calcium hydroxide–gypsum was observed using soft X-ray transmission microscopy. This technique allows the continuous imaging of the hydration process without the introduction of drying artifacts. Within minutes, microcrystalline hydrates covered the C3 A particles but over time large prismatic ettringite crystals are precipitated suppressing the microcrystalline hydrates. Within the resolution of the technique, no protective hydrated layer on the surface of C3 A particles was observed. 相似文献
12.
Linghong Zhang Lionel J. J. Catalan Raymond J. Balec rew C. Larsen Hassan Haji Esmaeili Stephen D. Kinrade 《Journal of the American Ceramic Society》2010,93(1):279-287
The effects of aliphatic sugar alcohols (e.g., threitol, xylitol, sorbitol) on the hydration of tricalcium silicate (C3 S) and ordinary portland cement (OPC) were investigated and compared with those of sucrose, a well-established cement set retarder. Only sugar alcohols which contain threo diol functionality retarded the setting of C3 S and OPC, their efficacy increasing with the number of threo hydroxy pairs and, to a smaller extent, with the overall population of hydroxy groups. None, however, were as effective as sucrose. The initial and final setting times increased exponentially with the concentration of saccharide, although the hydration of OPC was less inhibited than that of C3 S. Saccharides function as "delayed accelerators," that is, cement hydration is first inhibited and then proceeds faster than in saccharide-free cement. This behavior is consistent with the theory that the induction period is controlled by slow formation and/or poisoning of the stable calcium silicate hydrate (CSH) nuclei. The early inhibiting influence of saccharides on CSH precipitation is apparently stronger than on the growth of crystalline calcium hydroxide. Saccharides did not negatively affect the degree of hydration and compressive strength of fully set OPC paste; on the contrary, sorbitol yielded modest increases. 相似文献
13.
Donald E. Macphee Karen Luke Fred P. Glasser Eric E. Lachowski 《Journal of the American Ceramic Society》1989,72(4):646-654
Calcium silicate hydrate (C-S-H) gels are the principal bonding material in portland cement. Their solubility properties have been described, enabling pH and solubilities to be predicted. However, the gels also interact with other components of cements, notably alkalis. C-S-H has been prepared from lime and silicic acid in solutions of sodium hydroxide or potassium hydroxide and by the hydration of tricalcium silicate (C3 S) in sodium hydroxide solutions. Analyses of aqueous phases in equilibrium with 85 gels show that the aqueous calcium and silicon concentrations fit smooth curves over the range of increasing sodium concentrations. Where anomalous data occur, they correspond to solids with low lime contents: such gels are tentatively assumed to fall into a region where the presence of another gel phase influences the aqueous composition. Dimensional changes have been observed in the hydration products of C3 S as a function of alkali content and these may be relevant to the alkali-silica reaction. The significance of this and other data is discussed with reference to real cement systems. 相似文献
14.
Preparation of Portland Cement Components by Poly(vinyl alcohol) Solution Polymerization 总被引:2,自引:0,他引:2
Sang-Jin Lee Elizabeth A. Benson Waltraud M. Kriven 《Journal of the American Ceramic Society》1999,82(8):2049-2055
The four components portland cement-dicalcium silicate, C2 S (Ca2 SiO4 ); tricalcium silicate, C3 S (Ca3 SiO5 ); tricalcium aluminate, C3 A (Ca3 Al2 O6 ); and tetracalcium aluminate iron oxide, C4 AF (Ca4 Al2 Fe3 O10 )-were formed using a solution-polymerization route based on poly(vinyl alcohol) (PVA) as the polymer carrier. The powders were characterized using X-ray diffraction techniques, BET specific surface area measurements, and scanning electron microscopy. This method produced relatively pure, synthetic cement components of submicrometer or nanometer crystallite dimensions, high specific surface areas, as well as extremely high reactivity at relatively low calcining temperatures. The PVA content and its degree of polymerization had a significant influence on the homogeneity of the final powders. Two types of degree of polymerization (DP) PVA were used. Lower crystallization temperatures and smaller particle size powders were obtained from the low-DP-type PVA at optimum content. 相似文献
15.
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
16.
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
17.
Investigations of tricalcium silicate (C3 S) suspensions using different techniques have shown the initial hydration kinetics of C3 S are strongly dependent on the water/C3 S ratio. In order to provide new experimental data on the hydration, we have adapted a Tian-Calvet heat flow isothermal microcalorimeter to study thermal flow variation released by C3 S stirred suspensions in water and saturated lime water. We observed three exothemic peaks and one endothermic peak. Their relative magnitude and duration depend on the W/C ration and the lime solution concentration. The protective layer theory appears to be consistent with our results for high W/C ratio. Moreover, portlandite precipitation seems to be a consequence and not the cause of the acceleratory period. 相似文献
18.
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
19.
Paul Wencil Brown 《Journal of the American Ceramic Society》1993,76(12):2971-2976
Hydration reactions of C3 A and C4 AF with calcium sulfate hemihydrate and gypsum were investigated and the kinetics of the reactions compared. The rates of C3 A and C4 AF hydration, as determined by heat evolution, vary depending on whether the sulfate-containing reactant is gypsum or calcium sulfate hemihydrate. The following sequence of reactions involving C4 AF occurs when hemihydrate is the reactant: gypsum formation during the first hour, ettringite formation between 20 and 36 hours, and the conversion of ettringite to monosulfate over a period of about 12 hours. Monosulfate formation initiates prior to the complete consumption of gypsum. The onset of this conversion occurs at a shorter hydration time when hemihydrate is a reactant and the total amount of heat evolved is lower. The hydration reactions in saturated calcium hydroxide solution occur more slowly than those in water. Based on heat liberation, C4 AF reacts at a much higher rate than C3 A. Ettringite formation occurs during the first 8 to 9 days of C3 A hydration. Once the gypsum is consumed, ettringite converts to monosulfate during two additional days. Compared to gypsum, hemihydrate decreases the rates of hydration of both C3 A and C4 AF. The effects on the hydration characteristics of C4 AF are significant. The hydration of C3 A with gypsum in water, in saturated Ca(OH)2 solution, and in 0.3 M NaOH solution were compared. Heat evolution is the lowest for hydration in 0.3 M NaOH. The onset of monosulfate formation occurs prior to the complete reaction between gypsum and C3 A in the NaOH solution. 相似文献
20.
The concentration of ionic species in the solution in contact with hydrating dicalcium silicate (C2 S) has been studied as a function of time and in the presence of admixtures. The ionic product for calcium hydroxide increases quite slowly and saturation levels are not greatly exceeded at any time. Small quantities of C3 S control the ionic concentrations and cause considerable super-saturation with respect to calcium hydroxide. The implications of the present data with respect to C2 S hydration are discussed. 相似文献