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The impact of calcium aluminate cement hydration upon the properties of refractory castables
Monolithic refractory castables, bonded with calcium aluminate cements, have a rich history of over 80 years. They have evolved from high cement conventional formulations to the era of reduced cement castable systems that can be placed using a variety of techniques such as casting, gunning, self flow, pumping and shotcreting. These developments have been made possible by the versatility of the calcium aluminate cements which play a major role in determining the properties of such monolithic refractories. The usage chain of monolithics containing CAC (calcium aluminate cement) contains several steps such as mixing, placing and consolidation, curing and dry out and finally use in service. Each of these steps within the castable placing chain are intimately linked to the hydration process of CAC. In order to understand the role of CAC, it is first necessary to consider the reactions that take place within CAC during the hydration process and to then link these reactions to the physical aspects of the castable properties. Their cementitious properties enable the refractory to be cast in place and to set and harden under ambient conditions. As the refractory is heated to high temperature, the water needed for placing and the formation of hydration products is driven off and the hot strength is provided by sintering and ceramic bonding. This process of first heating or 'dry out' must be carefully managed to avoid undesirable strength loss, spalling or explosion. This review will investigate in detail the hydration and dehydration reactions that occur from the point that water is added at the beginning of mixing through to the point that the installed refractory lining is put into service. The effect of these reactions on the physical properties of the castables will be shown in a variety of systems. The impact of parameters such as temperature, mineralogy and other formulation components will be also reviewed.
The impact of calcium aluminate cement hydration upon the properties of refractory castables
Monolithic refractory castables, bonded with calcium aluminate cements, have a rich history of over 80 years. They have evolved from high cement conventional formulations to the era of reduced cement castable systems that can be placed using a variety of techniques such as casting, gunning, self flow, pumping and shotcreting. These developments have been made possible by the versatility of the calcium aluminate cements which play a major role in determining the properties of such monolithic refractories. The usage chain of monolithics containing CAC (calcium aluminate cement) contains several steps such as mixing, placing and consolidation, curing and dry out and finally use in service. Each of these steps within the castable placing chain are intimately linked to the hydration process of CAC. In order to understand the role of CAC, it is first necessary to consider the reactions that take place within CAC during the hydration process and to then link these reactions to the physical aspects of the castable properties. Their cementitious properties enable the refractory to be cast in place and to set and harden under ambient conditions. As the refractory is heated to high temperature, the water needed for placing and the formation of hydration products is driven off and the hot strength is provided by sintering and ceramic bonding. This process of first heating or 'dry out' must be carefully managed to avoid undesirable strength loss, spalling or explosion. This review will investigate in detail the hydration and dehydration reactions that occur from the point that water is added at the beginning of mixing through to the point that the installed refractory lining is put into service. The effect of these reactions on the physical properties of the castables will be shown in a variety of systems. The impact of parameters such as temperature, mineralogy and other formulation components will be also reviewed.
The impact of calcium aluminate cement hydration upon the properties of refractory castables
Einfluß der Hydratation von Calciumaluminatzement auf die Eigenschaften von gießfähigen Feuerfestmaterialien
Parr, Christopher (author) / Simonin, Fabien (author) / Touzo, Bruno (author) / Wöhrmeyer, Christoph (author) / Valdelievre, Benoit (author) / Namba, Akihiko (author)
2005
11 Seiten, 14 Bilder, 6 Tabellen, 28 Quellen
Article (Journal)
English
feuerfeste Gießmasse , keramisch gebundenes Feuerfesterzeugnis , Calciumaluminatzement , chemische Zusammensetzung , mineralogische Zusammensetzung , Wasserabbinden von Zement , hydrothermale Reaktion , Konduktometrie , Werkstoffeigenschaft , Verarbeitbarkeit , Zuschlagstoff , Reaktivität (Reaktionsfähigkeit) , Viskositätsindexverbesserer , Füllstoff , Dehydratation , Temperatureinfluss , Festigkeitserhöhung , Porosität
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