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Early formation of belite in cement clinker raw materials with slag
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Cementa AB, Malmö, Sweden.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Nordkalk AB, Köping, Sweden.ORCID iD: 0000-0002-8230-8847
R and D Cement Cementa AB, Stockholm, Sweden.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
2021 (English)In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 33, no 6, p. 249-256Article in journal (Refereed) Published
Abstract [en]

Analytical methods for characterising cement raw meal during heating in different atmospheres were investigated. The effect of replacing limestone with 10 wt% slag on the formation of incipient belite and precursors of the clinker liquid in the temperature range 600–1050°C was quantified using thermogravimetry, X-ray diffraction and equilibrium calculations. The results showed that when calculating the lime saturation factor, slags were favoured to sand, resulting in lower amounts of quartz and C2S in the samples containing slag than the reference sample. This suggests that silicon dioxide in slag minerals did not react in this temperature range. The multi-component equilibrium results supported the phase formation sequence established. Allowing for the possible kinetic influences the potential solids solutions offered with the software was a valuable asset. The results showed that the effect of using slags to reduce the carbonate and sand content in a raw meal on potential amounts of incipient C2S was negative. At present, more detailed knowledge is needed regarding how blast-furnace slag and basic oxygen furnace slag contribute to the formation of intermediary compounds such as incipient C2S, C3A, C2F and C4AF in the solid phase at temperatures over 1050°C and affect the formation of C3S.

Place, publisher, year, edition, pages
ICE Publishing , 2021. Vol. 33, no 6, p. 249-256
National Category
Ceramics
Identifiers
URN: urn:nbn:se:umu:diva-185292DOI: 10.1680/jadcr.19.00150ISI: 000662866700002Scopus ID: 2-s2.0-85108236894OAI: oai:DiVA.org:umu-185292DiVA, id: diva2:1574029
Available from: 2021-06-28 Created: 2021-06-28 Last updated: 2023-08-21Bibliographically approved
In thesis
1. Modeling the influence of magnesium from alternative raw materials on the chemistry of Portland cement clinker
Open this publication in new window or tab >>Modeling the influence of magnesium from alternative raw materials on the chemistry of Portland cement clinker
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Modellering av inverkan av magnesium från alternativa råmaterial på Portland cementklinker kemi
Abstract [en]

The methods used in this thesis work were a combination of computational and modeling based laboratory experiments.

Thermodynamic process modeling of the cement clinker process offers a tool for evaluating how changes in raw materials and process parameters affect the clinker quality. Work with finding suitable replacement raw materials involves investigating the chemical compatibility of potential alternative materials. Such replacement materials may be metallurgical slags, although there are some unsolved issues with the quantities of certain metals and particularly Mg in these materials.

For predicting the formation of clinker mineral phases, cooling calculations are used in order to reproduce the temperature history in the full scale process. A chemistry model including a solid solution phase based on C2S and phosphate was developed along with the recommendation for continued work on clinker phases with solid solutions to include MgO. A thermodynamic database for phase chemistry calculations of clinkering reactions was created and evaluated. Suitable compounds and solution species were selected from the thermochemical database included in FactSage software. The extent and quality of the required thermodynamic data via available databases is generally satisfactory, except for certain properties of some of the main clinker phases. One example is the lack of a thermodynamic model for the alite solid solution. That is, the composition of the phase available in the database representing alite does not contain the minor elements Al, Fe and Mg. Therefore, it is difficult to predict the quantity and distribution of Mg in the clinker, with varying total content of MgO. Thus, one of the goals/objectives was to improve thethermodynamic model of alite as a solid solution of 3CaO-SiO2-xAl2O3-yFe2O3-zMgO. To achieve this, it was assumed that a mix of compounds with adjusted Henrian coefficients representing the solid solution clinker phase alite was in equilibrium with the clinker melt.

The distribution of MgO was studied in synthetic clinker compositions with quantities ranging from 0.5 to 10 wt-%. Synthetic clinker mixes were heated to 1450°C and studied with Rietveld refinements of X-ray diffraction data and SEM-EDS analysis. In addition, the mechanisms of how slag and lime particles react facilitating the diffusion of MgO into the developing clinker melt and the formation of incipient belite were studied.

The calculated results provide a good prediction of the quantities and composition of the clinker phases formed during heating and non-equilibrium cooling. The solubility of MgO in the clinker and the quantity of periclase formed is in fair agreement with published data. Thus, this thesis work shows that using a mix of compounds with adjusted activities in alite together with available standard thermodynamic data and the Scheil cooling method had good potential for evaluating alternative raw materials.

Also, the work has identified weak points in the process modeling and suggest improvements to be made in future research work.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2023. p. 94
Keywords
Thermodynamic modeling, process modeling, Portland cement, clinker, periclase, magnesium oxide, alite, Scheil calculation, solid solutions
National Category
Physical Chemistry Chemical Process Engineering
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-213098 (URN)9789180700863 (ISBN)9789180700856 (ISBN)
Public defence
2023-09-14, Aula Biologica, Biologihuset, Umeå, 13:00 (Swedish)
Opponent
Supervisors
Funder
Vinnova, 2014-04073Vinnova, 2015-02519Vinnova, 2015-04541Swedish Energy Agency
Available from: 2023-08-24 Created: 2023-08-21 Last updated: 2023-08-22Bibliographically approved

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Viggh, ErikEriksson, MatiasBackman, Rainer

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