HAL Id: hal-00669016 https://hal.archives-ouvertes.fr/hal-00669016 Submitted on 13 Feb 2012 HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. CALPHAD formalism for Portland clinker: thermodynamic models and databases Marie-Noëlle De Noirfontaine, Sandrine Tusseau-Nenez, Caroline Girod-Labianca, V. Pontikis To cite this version: Marie-Noëlle De Noirfontaine, Sandrine Tusseau-Nenez, Caroline Girod-Labianca, V. Pontikis. CAL- PHAD formalism for Portland clinker: thermodynamic models and databases. Journal of Materials Science, Springer Verlag, 2012, 47 (3), pp.1471-1479. <10.1007/s10853-011-5932-7>. <hal-00669016>
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HAL Id: hal-00669016https://hal.archives-ouvertes.fr/hal-00669016
Submitted on 13 Feb 2012
HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, estdestinée au dépôt et à la diffusion de documentsscientifiques de niveau recherche, publiés ou non,émanant des établissements d’enseignement et derecherche français ou étrangers, des laboratoirespublics ou privés.
CALPHAD formalism for Portland clinker:thermodynamic models and databases
Marie-Noëlle De Noirfontaine, Sandrine Tusseau-Nenez, CarolineGirod-Labianca, V. Pontikis
To cite this version:Marie-Noëlle De Noirfontaine, Sandrine Tusseau-Nenez, Caroline Girod-Labianca, V. Pontikis. CAL-PHAD formalism for Portland clinker: thermodynamic models and databases. Journal of MaterialsScience, Springer Verlag, 2012, 47 (3), pp.1471-1479. <10.1007/s10853-011-5932-7>. <hal-00669016>
CALPHAD formalism for Portland clinker: thermodynamic models and databases
M.-N. de Noirfontaine1,2,∗, S. Tusseau-Nenez2,3, C. Girod-Labianca2,4, V.
Pontikis2
1 LSI, CNRS UMR 7642 - Ecole Polytechnique, 91128 Palaiseau, France 2 CECM, CNRS UPR 2801, 94407 Vitry-sur-Seine, France 3 ICMPE, CNRS UMR 7182 – Université Paris XII, 94320 Thiais, France 4 CTG-Italcementi Group, les Technodes, 78931 Guerville, France
Abstract (150-250 words): 239 words
The so-called CALPHAD method is widely used in metallurgy to predict phase diagrams
of multi-component systems. The application of the method to oxide systems is much more recent,
because of the difficulty of modelling the ionic liquid phase. Since the 1980s, several models have
been proposed by various communities. Thermodynamic databases for oxides are available and
still under development.
The purpose of this article is to discuss the distinct approaches of the method for the
calculation of multi-component systems for Portland cement elaboration. The article gives a state
of the art of the most recent experimental data and the various calculations for the CaO-Al2O3-
SiO2 phase diagram. A literature review of the three binary sub-systems leads to main conclusions:
(i) discrepancies are found in the literature for the selected experimental data, (ii) the phase
diagram data in the reference books are not complete and up to date and (iii) the two-sublattices
model and the modified quasichemical model can be equally used for the modelling of the
aluminates liquid. The predictive feature of the CALPHAD method is illustrated using the CaO-
Al2O3-SiO2 system with the two-sublattices model: extrapolated (predicted) and fully-assessed
phase diagrams are compared in the clinkering zone of interest. The recent application of the
predictive method for the calculations of high-order systems (taking into account Fe2O3, SO3,
CaF2, P2O5) shows that the databases developed with the two-sublattices model and the modified
Portland cement is obtained by grinding an artificial rock, called the
clinker, with a small amount of gypsum (~5%) added in order to delay the setting
time of cement. The clinker is produced by heating a mixture of limestone (~80
wt%) and clay (~20 wt%) up to the so-called clinkering temperature (Tc) in the
range of 1400-1500 °C. The clinker contains four compounds at least. The two
major phases are solid solutions of two calcium silicates, Ca3SiO5 and Ca2SiO4,
referred to as alite and belite, respectively. The two other phases are solid
solutions of two calcium aluminates, Ca3Al2O6 and Ca4Al2Fe2O10. Hereafter, we
use the compact mineralogical notation: C=CaO, S=SiO2, A=Al2O3, F=Fe2O3. The
four compounds are designated as C3S, C2S, C3A and C4AF.
Understanding the quaternary phase diagram CaO-SiO2-Al2O3-Fe2O3
(hereafter referred to as ‘CASF’ system) is the basis of the chemistry in the kiln.
Table 1 summarises the four main zones and successive reactions between 400 °C
and Tc. The ternary phase diagram CaO-Al2O3-SiO2 (referred to as ‘CAS’ phase
diagram) is often used for a preliminary understanding of Portland cements.
Rankin was the first to determine such a diagram [1]. It is particularly relevant for
the fabrication of white cements that are characterised by a very small Fe2O3
content. Figure 1 shows the composition area of Portland cements in the ‘CAS’
system. For white cements, melting temperatures (Tm) and clinkering
temperatures (Tc) are about 1380 °C and 1500 °C, respectively. At Tc=1500 °C,
the three phases in equilibrium are C3S, α-C2S and the aluminates liquid of
composition Lc. The respective Lc compositions for 1500 and 1400 °C are: CaO
(~59 wt%), Al2O3 (~32 wt%), SiO2 (~9 wt%) and CaO (~55 wt%), Al2O3 (~37
wt%), SiO2 (~8 wt%). In the quaternary ‘CASF’ system, the temperature of the
liquidus is reduced down to Tm=1338 °C. The composition and the proportion of
liquid depend on the weight ratio A/F. The proportion of liquid rises up to 15-25
wt% [2]. The Fe2O3 proportion in the liquid is in the 5-14 wt% range, for A/F
values in the 6.06-0.64 wt% range [3].
The chemistry in the kiln is often modified by the impurities (the so-called
minors) introduced during the elaboration process. These impurities are
introduced by the rocks, the additives or the fuels. They play an important role
during the clinkering process. In some cases, impurities such as SO3 or MgO
change the composition of the interstitial melt [4, 5], leading preferentially to the
polymorph M1 or M3 of alite in the clinker [6]. In other cases, minor oxides such
as CaF2 or MgO may lower temperatures Tm and Tc [3], and reduce both the CO2
emissions and the energy consumption for the fabrication of cement. Since the
1990s, the cement industry has used more and more alternative fuels (ratio up to
1/3), in order to favour the valorization of wastes and reduce the use of fossil
fuels. This was the origin of new experimental studies related to the effects of
minors, such as phosphorus when meat and bone meals are burnt [7]. These
studies highlight the lack of knowledge of multi-component equilibrium phase
diagrams. In addition, the knowledge of multi-components phase diagrams for
clinker manufacturing is also motivated by the research of new compositions of
cement within the context of CO2 emission reduction.
Table 1 Portland clinker formation: main zones and reactions from 400 °C to 1500 °C in a typical
dry-process rotary kiln. In modern plants with preheater towers, the dehydration and initial
calcinations take place out of the kiln in the preheater tower.
Zones T (° C) Reactions
Dehydration 400- 600 Deshydroxylation of clay ( H2O) 600- 900 Decomposition of clay, with formation of reactive oxide mixture: SiO2, Al2O3, Fe2O3Calcination 600- 1000 Decomposition of limestone ( CO2) with formation of reactive oxide CaO
Formation of C2S and initial compounds C12A7, CA and C2F 1000-1300 Formation of C2S, C3A, C4AF Clinkering 1320-1380 (Tm) Melting of C3A and C4AF 1400-1500 (Tc) Formation of clinker (clinkering) with formation of C3S: CaO + C2S → C3S
Three phases in equilibrium: C3S + C2S + Liquid of aluminates (15-25 wt%)
0
10
20
30
40
50
60
70
80
90
100
Mas
s %
SIO
2
0 10 20 30 40 50 60 70 80 90 100 Mass % AL2O3
C3S
C2S
C3ACaO Al2O3
SiO2 Portland cements
Blast furnace slags
Alumina cements
Tiles and bricks
Fly ashes
Glasses
0
10
20
30
40
50
60
70
80
90
100
Mas
s %
SIO
2
0 10 20 30 40 50 60 70 80 90 100 Mass % AL2O3
C3S
C2S
C3ACaO Al2O3
SiO2 Portland cements
Blast furnace slags
Alumina cements
Tiles and bricks
Fly ashes
Glasses
3
4
Fig. 1. Zone of Portland cements in the ‘CAS’ system (white cements). Composition of the three
5. Towards thermodynamic databases for cement materials
This last part compares advances of the available oxide databases
developed with the three models (associated, modified quasichemical and ionic
two-sublattice models) to compute the quaternary system CaO-SiO2-Al2O3-Fe2O3
(‘CASF’) and to take into account minor oxides such as MgO, SO3, P2O5 and
alkalis.
The calculation of the quaternary phase diagram ‘CASF’ requires the
knowledge of the ‘CAS’ system and the three other ternary phase diagrams: CaO-
Al2O3-Fe2O3, CaO-SiO2-Fe2O3, and Al2O3-Fe2O3-SiO2. All the three binary sub-
systems (CaO-Fe2O3, Al2O3-Fe2O3, and SiO2-Fe2O3) have been fully optimized
16
with the three models [18, 67-69] except the Al2O3-Fe2O3 system that has not
been evaluated yet with the two-sublattice model (ION3 database). FToxid
database recently included Fe2O3: the ternary solid compound C4AF is modelled
and the ternary and higher order liquids are well extrapolated. NPL oxide database
takes into account Fe2O3 as well as for C4AF as for the liquid.
For the case of MgO oxide, data are available in the literature. The three
ternary systems Al2O3-CaO-MgO, Al2O3-MgO-SiO2 and CaO-MgO-SiO2 have
been fully assessed, both with the two-sublattice model [28, 70, 71] and the
modified quasichemical model [72, 73]. As far as there is no quaternary solid
compound stabilized in the Portland clinker zone, extrapolation to the quaternary
system CaO-Al2O3-SiO2-MgO is applied in the various databases.
For the other minor oxides of interest, the situation is very different.
Because the modelling of oxides and commercial interests are still recent, no
optimized data for the binary phase diagrams of CaO, SiO2 or Al2O3 with SO3,
CaF2 or P2O5 have been published. However, FT-oxid database has recently
included SO3 [19], CaF2 and alkalis (Na2O, K2O) and can be used for cement
industry. The Gibbs energy modelling of phosphate phases is already in progress
and need further investigations.
6. Conclusion
Based on a literature review, we have pointed out that some
discrepancies still remain concerning several melting points and that the phase
diagram data in the current cement reference books are not complete and up to
date. We have also shown that both the two-sublattices model and the modified
quasi-chemical model for liquids are relevant up to the calculation of the ternary
CaO-Al2O3-SiO2 (‘CAS’) system. Differences between the calculations depend on
the choice of the selected experimental data for the assessments. The predictive
feature of the CALPHAD method for the calculation of multi-component phase
diagrams is illustrated on the ‘CAS’ ternary phase diagram. As there are no strong
17
ternary interactions in the clinkering zone of interest, a relevant preliminary phase
diagram can be obtained from extrapolation. This predictive method appears as a
useful tool to estimate the composition Lc and the proportion of liquid in the
clinkering zone. For the time being, the composition Lc can be obtained with
average deviations from experiments of about 3-4 wt% SiO2 and 5 wt% Al2O3.
Additional assessments ought to be performed for a better accuracy around the Lc
composition.
The CALPHAD methodology is applied in commercial databases (NPL
oxide, FToxid and ION3) for further calculations of higher order systems, in
particular including Fe2O3, MgO, SO3, P2O5 and alkalis. Considering the data
published up to now, the thermodynamic modelling of iron (or other minor
elements)-containing liquids have not reached the same level of relevance for the
three models. Since a decade, Factsage and MTDATA communities develop the
most extensive databases for cement industry, based on the associated and
modified quasichemical models.
Acknowledgements
CTG-Italcementi Group financially supported this study, within the research collaboration
framework between the CECM (CNRS, France) and CTG (Italcementi Group, France)
laboratories. The authors acknowledge B. Bollotte, E. Moudilou and F. Amin (CTG) for valuable
discussions. Many thanks to G. Inden, Bo Sundman, J.-M. Joubert and P. Chartrand for fruitful
discussions about Calphad method, models and softwares. The authors also express their sincere
thanks to H. Szwarc and R. Céolin for advice and are warmly thankful to F. Dunstetter for his
critical reading of the manuscript.
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