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The sintering and the structure of clinkers, modified by the introduction of different ionic forms of sulfur and phosphorus
into the raw mix, were examined. One reference synthetic mixture and 25 modified mixtures were prepared by mixing the reference
sample with 0.5, 1.0, 1.5, 2.0 and 2.5%w/w of chemical grade CaSO4, CaS, Ca3(PO4)2, CaHPO4 and Ca(H2PO4)2. Free lime content in all samples was measured. The sintering reactions in samples were recorded by means of differential
thermal analysis. The texture of the clinkers was examined using a scanning electron microscope and EDX. It is concluded that,
despite of their relatively low doping concentration in the raw mix, P and S affect considerably its reactivity and the texture
of the clinker. The various ionic forms of the same element (SO4
2-, S2- for S, PO4
3-, HPO4
2- and H2PO4
- for P) exhibit a different and unequivocal effect on the reactivity of the synthetic raw mix and on the texture of the corresponding
clinkers. S (in both forms) and P (added as HPO4
2-) are mainly dissolved in the melt and they have a positive effect on the burnability of the raw mix. P (added as PO4
3- or H2PO4-) is preferentially accumulated in belite. In this case further stabilization of β-C2S occurs and the binding of the free lime is hindered.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
S. Tsivilis G. Kakali E. Chaniotakis A. Souvaridou 《Journal of Thermal Analysis and Calorimetry》1998,52(3):863-870
Subject of this paper is to investigate the hydration process of Portland limestone cement containing 10-35% limestone. Cements,
produced by co-grinding of clinker, limestone and gypsum, were hydrated for periods 6 h to 28 d and were studied by means
of TG and XRD. The Ca(OH)2 content of the cements containing limestone is higher than in pure cements, specifically for 10% limestone content and ages
more than 1 day. These results are in accordance with the strength development of the studied cements. In earlier ages the
Ca(OH)2 content is slightly lower in the limestone cements and independent of the limestone content. After 1 day curing, the increase
of limestone addition causes a relative increase of the non evaporable water. The XRD patterns indicated the presence of carboaluminates
in the hydrated limestone cements.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
M. Kaloumenou E. Badogiannis S. Tsivilis G. Kakali 《Journal of Thermal Analysis and Calorimetry》1999,56(2):901-907
This paper reports an investigation of the effect of the particle size of kaolin on its transformation to metakaolinite. Kaolin
from the island of Milos was either crushed or ground in order to produce four samples with different degrees of fineness
(residue at 500 μm: 0–71.8%). The samples were treated thermally under different conditions in order to determine the optimum
treatment conditions. The conversion of kaolinite to metakaolinite and the structural changes in the material during treatment
were investigated by means of TG and XRD, respectively. Each sample was incorporated into a type I cement, at 20% by mass
of cement, and the compressive strengths of the resulting blended cements were measured. It is concluded that the particle
size of the raw kaolin does not affect the thermal conversion or the pozzolanic activity of the material. The use of crushed
kaolin has many benefits since the furnace load can be increased, while the grinding process is needed only to reduce the
size of the metakaolinite particles.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Perraki M. Perraki T. Kolovos K. Tsivilis S. Kakali G. 《Journal of Thermal Analysis and Calorimetry》2002,70(1):143-150
The sintering and hydration processes of a modified cement raw mix were examined using thermal analysis techniques. One reference
and four modified mixtures, prepared by mixing the reference sample with 0.5, 1.0, 1.5 and 2.0 % w/w of a wolframite-stibnite mineral were studied. The clinkering reactions were recorded and the total enthalpy change during
the sintering was determined by means of a differential scanning calorimetry. The combined water and the Ca(OH)2 content in samples hydrated for 1 to 28 days were determined, using thermogravimetry. As it is concluded, the effect of the
added mineral on the sintering and hydration reactions can be fully recorded and evaluated using thermal analysis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
G. Kakali E. Chaniotakis S. Tsivilis E. Danassis 《Journal of Thermal Analysis and Calorimetry》1998,52(3):871-879
DSC was used in order to evaluate the reactivity of cement raw meal. Two groups of samples were studied: five industrial raw
meals for ordinary Portland cement production, with similar compositions, but differences in granulometry; and five industrial
raw meals for white Portland cement production, with similar granulometric features, but different compositions. The burnability
indices of the samples were correlated with certain data obtained from the DSC curves. It is concluded that the DSC curve
data, and especially the temperature and enthalpy effect of belite formation, are strongly correlated with the burnability
of the cement raw meal. The temperature of belite formation is affected by chemical and mineralogical factors, while the enthalpy
effect is additionally affected by the fineness of the raw meal.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
In this paper the effect of limestone, fly ash, slag and natural pozzolana on the cement hydration products is studied. Four
composite cements containing limestone, natural pozzolana from the Milos Island, slag and fly ash have been produced by intergrinding
clinker (85%), the above main constituent (15%) and gypsum. The grinding process was designed in order to produce cements
of the same 28d compressive strength. The hydrated products, formed after 1–28 days, were studied by means of X-ray diffraction.
Unhydrated calcium silicate compounds of clinker and hydration products such as C*H, C*S*H and ettringite are clearly observed.
Although there is not significant differentiation among samples hydrated for the same period of time, modifications of calcium
aluminate hydrates as well as sulfoaluminate hydrates, are indicated by the XRD patterns. In samples of limestone cement,
monocarboaluminate is formed in the first 24 hours and is still present after 28 days. 相似文献
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