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The thermodynamic calculations performed to determine the free enthalpy of reaction and to develop the partial pressure diagrams make it possible to define optimal basic conditions for the formation of sulpho minerals during the production of Portland cement clinkers. Among the decisive factors influencing this are the CO, O2 and SO3 partial pressure in the gaseous phase, CaOfree content at the end of clinker formation and the burning temperature. The formation of sulpho minerals is possible not only from starting raw materials, but also from the clinker minerals already formed. The results of the thermodynamic calculations indicate that the temperature stability of sulpho minerals can decrease considerably because of the actually excessively low O2 partial pressure in the kiln waste gases and the free lime present in the kiln charge. In order to avoid this, the CaSO4 carrier should be introduced into the kiln region surrounding the second half of the sinter zone and the cooling zone. The results of the experimental studies allow one to conclude that the calcium sulphate necessary for the formation of sulphoalite is supplied to the alite at least by the highly basic clinker melt arising at the end of clinker formation. The most important new X-ray reflections arising during this have been assigned to the sulphoalite identified by means of electron beam microanalysis. The new sulphoalite-containing cement has versatile constructional properties, which can be deliberately varied over a wide range. The swelling properties of the newly produced cement, with extremely high early and late setting strength, can be adjusted from shrinkage-free to high-expansion and self-stressing by varying the chemical composition of the raw meal used for the clinker sintering and via the content of CaSO4 carriers introduced into the kiln.
The thermodynamic calculations performed to determine the free enthalpy of reaction and to develop the partial pressure diagrams make it possible to define optimal basic conditions for the formation of sulpho minerals during the production of Portland cement clinkers. Among the decisive factors influencing this are the CO, O2 and SO3 partial pressure in the gaseous phase, CaOfree content at the end of clinker formation and the burning temperature. The formation of sulpho minerals is possible not only from starting raw materials, but also from the clinker minerals already formed. The results of the thermodynamic calculations indicate that the temperature stability of sulpho minerals can decrease considerably because of the actually excessively low O2 partial pressure in the kiln waste gases and the free lime present in the kiln charge. In order to avoid this, the CaSO4 carrier should be introduced into the kiln region surrounding the second half of the sinter zone and the cooling zone. The results of the experimental studies allow one to conclude that the calcium sulphate necessary for the formation of sulphoalite is supplied to the alite at least by the highly basic clinker melt arising at the end of clinker formation. The most important new X-ray reflections arising during this have been assigned to the sulphoalite identified by means of electron beam microanalysis. The new sulphoalite-containing cement has versatile constructional properties, which can be deliberately varied over a wide range. The swelling properties of the newly produced cement, with extremely high early and late setting strength, can be adjusted from shrinkage-free to high-expansion and self-stressing by varying the chemical composition of the raw meal used for the clinker sintering and via the content of CaSO4 carriers introduced into the kiln.
Sulphoalite-containing Portland cement clinkers for high performance cements
Lörke, P. (author)
2002
12 Seiten, 4 Bilder, 2 Tabellen, 5 Quellen
Conference paper
English
Sulfoaluminat , Portlandzementklinker , Hochleistungskeramik , Thermodynamik , Reaktionsenthalpie , Partialdruck , Kohlenmonoxid , Sauerstoff , Schwefeltrioxid , gasförmiger Aggregatzustand , Calciumoxid , Abgas , Brenntemperatur , Brennverhalten , Kalk , Zementdrehrohrofen , Calciumsulfat , Röntgenbeugung , Elektronenstrahlmikroanalyse , Quellvermögen , Wasserabbinden von Zement , Schrumpfung , Expansion , chemische Zusammensetzung , Rohstoff
Sulphoalite-containing Portland cement clinkers for high performance cements
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