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Calcium aluminates
About: Calcium aluminates is a research topic. Over the lifetime, 490 publications have been published within this topic receiving 9200 citations.
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26 May 2016-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the existing form of CaS inclusion in Ca-treated, Al-killed steel during secondary refining process was investigated with scanning electron microscopy and an energy-dispersive spectrometer (EDS).
Abstract: The existing form of CaS inclusion in Ca-treated, Al-killed steel during secondary refining process was investigated with scanning electron microscopy and an energy-dispersive spectrometer (EDS). The results of 12 heats industrial tests showed that CaS has two kinds of precipitation forms. One form takes place by the direct reaction of Ca and S, and the other takes place by the reaction of CaO in calcium aluminates with dissolved Al and S in liquid steel. Thermodynamic research for different precipitation modes of CaS under different temperature was carried out. In particular, CaO-Al2O3-CaS isothermal section diagrams and component activities of calcium aluminates were calculated by the thermodynamic software FactSage. By thermodynamic calculation, a precipitation-area diagram of oxide-sulfide duplex inclusion was established by fixing the sulfur content. The quantity of CaS, which was precipitated in a reaction between [Al], [S] and (CaO), can be calculated and predicted based on the precipitation-area diagram of oxide-sulfide duplex inclusion. Electron probe microanalysis and EDS were used for observing rolling deformation of different types of CaS-bearing inclusions during the rolling process. Low modification of calcium aluminates wrapped by CaS has different degrees of harm to steel in the rolling process. A thick CaS layer can prevent some fragile calcium aluminates from being crushed during the rolling process. Some oxide-sulfide duplex inclusion contains little CaS performed better deformation during the rolling process, but when CaS in oxide-sulfide duplex inclusion becomes more, it will cause the whole inclusion to lose plastic yielding ability. The plastic deformation region of CaS-bearing inclusion in a CaO-Al2O3-CaS isothermal section diagram is confirmed.
34 citations
TL;DR: In this paper, the authors used thermal analysis for identification of the various hydrates that can form in calcium aluminates cements, especially at early stages of hydration when poorly crystalline phases are present.
Abstract: The hydration of calcium aluminates cements is dominated by that of CA, CaAl2O4, which is a major constituent of all of them. At ambient temperatures, CAH10 and an amorphous phase are formed initially, but these are metastable and slowly (or more rapidly if exposed to higher temperatures) transform into C3AH6 and gibbsite. This conversion reaction is accompanied by and increase in porosity, which can lead to a loss in strength and vulnerability to chemical attack. Various methods of thermal analysis have been applied as a routine test to determine the degree of conversion, and the results from these methods are critically evaluated. Thermal analysis is a useful technique for identification of the various hydrates that can form in these systems, especially at early stages of hydration when poorly crystalline phases are present. Differential thermal analysis curves showing peaks attributable to all these hydrates are presented and it is shown that overlap frequently occurs, leading to difficulties in interpretation, which can sometimes be minimized by use of a complementary technique such as X-ray diffraction.
34 citations
TL;DR: Differential scanning calorimeter has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively.
Abstract: Differential scanning calorimeter (DSC) has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively. Dehydration of CAH10 and C2AH8 (whereH=H2O) occur ∼ at 160–180°C and 200–280°C respectively. These two phases are unstable and ultimately get transformed to AH3 and C3AH6. Dehydration of AH3 and C3AH6 occur between 290 and 350°C and overlap at lower scanning rate. The activation energy for dehydration of the stable AH3 and C2AH6 phases has been found to be 107.16 and 35.58 kJ mol−1 respectively. The compressive strength of the hydrated calcium aluminates has been determined. The result shows that in the case of CA, almost 90% of ultimate strength has been attained in 1 day whereas in CA2, ultimate strength has been attained in 14 days and in C12A7 in 1 day. DSC results have been correlated with the rate of strength developments.
33 citations
TL;DR: In this paper, the capacity of a number of calcium aluminates (C3A, C12A7, CA and C4A3 S ¯ ) to activate ternesite hydraulic reactivity was explored.
33 citations
TL;DR: In this paper, a kinetic study of delayed ettringite formation in hydrated Portland cement paste by XRD analysis over the temperature range 5 to 85 °C is reported.
33 citations