Technical Paper Reference : TP-GB-RE-LAF-097 Kerneos 8, Rue des Graviers - 92521 Neuilly sur Seine Cedex, France Tel. : +33 1 46 37 90 00 - Fax : +33 1 46 37 92 00 NEW CALCIUM ALUMINATES WITH IMPROVED CORROSION RESISTANCE FOR THE NEXT GENERATION OF REFRACTORY MONOLITHICS C. Parr, G. Assis, C. Wöhrmeyer, H. Fryda, G. Bhattacharya Kerneos SA, Paris, France Presented at the 9th Indian International Refractories Congress, Kolkata, 2 nd - 4 th February 2012 Page : 1/13
Transcript
Technical Paper Reference : TP-GB-RE-LAF-097
Kerneos 8, Rue des Graviers - 92521 Neuilly sur Seine Cedex, FranceTel. : +33 1 46 37 90 00 - Fax : +33 1 46 37 92 00
New CalCium alumiNates with improved CorrosioN resistaNCe for the Next GeNeratioN of refraCtory moNolithiCs
C. Parr, G. Assis, C. Wöhrmeyer, H. Fryda, G. Bhattacharya
Kerneos SA, Paris, France
Presented at the 9th Indian International Refractories Congress, Kolkata, 2nd - 4th February 2012
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Technical Paper
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ABSTRACT
By changing the microstructure of a monolithic castable it is possible to enhance the in-situ lining performance and ultimately, to increase the service life of the refractory. To achieve this, novel calcium aluminates (CA) have recently been developed, namely a 50% alumina (Al2O3) containing CA aggregate and a calcium magnesium aluminate (CMA) binder. Calcium aluminates can not only provide the binder function but can also add to and enhance the final performance as measured by corrosion resistance.
Reference : TP-GB-RE-LAF-097
Kerneos 8, Rue des Graviers - 92521 Neuilly sur Seine Cedex, FranceTel. : +33 1 46 37 90 00 - Fax : +33 1 46 37 92 00
Technical Paper
1 Introduction
The first part of this study looks at the influence of a calcium aluminate aggregate, namely R50, on the properties of a refractory castable in comparison to bauxite and fireclay aggregates. R50 aggregate contains hydraulic phases like calcium mono-aluminate that allow the surface of this aggregate to react chemically during hydration and de-hydration with the calcium aluminate cement in the binder phase, unlike other aggregates consisting of CA6, corundum or mullite. The chemical bonds between the R50 aggregate and the matrix enhance the physical properties of the castable.
In contact with aluminium, traditional bauxite- based mixtures require anti-wetting agents to reduce metal infiltration. However, these can negatively influence the refractoriness of the castable if the temperature of the aluminium furnace is raised above normal operating conditions. If temperatures reach unexpectedly high levels (>1200 °C), traditional anti-wetting additives like barium sulphate or calcium fluoride can destroy a bauxite-based castable. Castables made from R50, however, show superior infiltration resistance against aluminium alloys in aluminium contact areas with significantly lower (or no) anti-wetting agent additions. Minimising the use of the antiwetting agent and using R50 enhances the refractoriness of the castable up to 1400°C. This makes R50 interesting for many applications where good heat containment, abrasion resistance and low liquid penetration / low accretion build-up are required.
In the second part of this paper we will discuss the new CMA binder that brings microcrystalline spinel phases into areas of the castable microstructure which are normally occupied by calcium aluminate phases only. The basis of this new calcium magnesium aluminate cement is a novel multiphase clinker with a microstructure of CA phases embedded in a matrix of microcrystalline magnesium aluminate spinel crystals. Using this novel CMA as a binder in different types of ladle castables has shown significant improvements in corrosion and penetration resistance with a wide range of ladle slag compositions.
2 Experimental Procedure
2.1 Material Details : CA aggregateR50 is a low iron oxide, fused calcium aluminate aggregate with a very low C12A7 content (<1%), a high amount of calcium mono-aluminate (CA) and a small amount of gehlenite (C2AS). The specific mineralogy of the R50 aggregate facilitates not only the formation of physical bonds but, more importantly, chemical bonds between the surface of the R50 and the CA cement in the matrix. This ensures the low porosity structure of the castable which significantly enhances the final performance of the castable system. The R50 will be compared mainly with a Chinese bauxite (Tab. 1) to explore its potential in applications where abrasion resistance, low liquid penetration and / or low accretion formation is required.
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Technical Paper Reference : TP-GB-RE-LAF-097
Table 1 : Chemistry and mineralogy of aggregates. R50 Bauxite
2.2 Test methods : Aggregate TestingClassical monolithic refractory test methods such as vibration flow, porosity by water immersion and strength measurements have been used to study the basic castable properties. Quantitative chemical and mineralogical analyses have been conducted using the XRF and XRD methods. The aggregates have been tested in a deflocculated medium cement castable (MCC) formulation (Tab. 2).
3 Experimental Results & Discussion3.1 Aggregate testingPrevious work has shown[1] that R50 provides a very similar castable rheology in conventional formulations. This is because R50 is a fused and almost pore free aggregate, minimising the casting water required and ensuring that there is no flow decay during placing. In addition, the mineralogy of the R50 (with its high calcium monoaluminate and low C12A7 content) ensures that early stiffening is prevented and working time maintained.
For this work, microsilica-free MCC formulations (Tab. 2) were chosen in order to minimise the chemical reactions between the aluminium melt and the castable matrix. Different contents of barium sulphate (BaSO4) were used as an anti-wetting agent. The corrosion and penetration resistance was tested in contact with liquid aluminium. The BaSO4 addition is absolutely necessary for the bauxite based castables to minimise metal infiltration of the castable, but the results below will show that the addition can be reduced or even completely eliminated when R50 is used[1, 2].
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Table 2 : Model MCC recipes with bauxite (B1-B3) and R50 (R1-R3) with different barium sulphate contents.
Bauxite R50 B1 B2 B3 R1 R2 R3
R50 3-5 mm % - 33R50 1-3 mm % - 12R50 0-1 mm % - 20SECAR® 51 % - - 5 5Bauxite 3-6 mm % 21 -Bauxite 1-3 mm % 22 -Bauxite 0-1 mm % 22 -Bauxite 0-0.09 mm % - 5 5 -Calc. Alumina % - - 5 - - 5BaSO4 % 10 5 - 10 5 -
A polycarboxylate ether (Peramin® AL200) deflocculates and fluidifies these castables very efficiently with 5% water in case of bauxite and only 4.5% in case of R50. Despite the lower water addition and a lower deflocculant level, better flow properties were achieved for all R50 containing MCC’s (R1-R3) (Fig. 3). The open porosity after firing to 800 & 1200°C, the critical temperature range for aluminium applications, is, in all cases, significantly lower with R50 despite these castables also having lower bulk densities (Fig. 4, 5). The cold crushing strength of the R50 formulations (irrespective of the BaSO4 content) is higher than formulation B1 (10% BaSO4) which could be considered as the reference formulation for this application (Fig. 6).
150
160
170
180
190
200
210
220
230
0 30 60Time (min)
Vibr
atio
n flo
w (m
m)
R1R3R2B1B3B2
Fig. 3 : Vibration flow for R50 (R1-R3) and bauxite (B1-B3).
5
7
9
11
13
15
17
19
21
B1 B2 B3 R1 R2 R3Castable
App.
Por
osity
(Vol
.%)
800°C 1200°C
Fig. 4 : Apparent porosity for R50 (R1-R3) and bauxite (B1-B3).
2,52,55
2,62,65
2,72,75
2,82,85
2,92,95
3
B1 B2 B3 R1 R2 R3Castable
Bulk
den
sity
(Vol
.%)
800°C 1200°C
Fig. 5 : Bulk density for R50 (R1-R3) and bauxite (B1-B3).
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0
50
100
150
200
250
B1 B2 B3 R1 R2 R3Castable
CC
S (M
Pa)
800°C 1200°C
Fig. 6 : Cold crushing strength of MCC with R50 (R1-R3) and bauxite (B1-B3).
To simulate the in situ performance of these castable formulations given in Tab. 2, static corrosion tests in ‘Alcoa cups’ cast from each formulation were performed . The cups were filled with aluminium alloy 7075, heated to 800°C and held at this temperature for 72 hours. Thereafter, the cups were emptied, cooled and sectioned.
Fig. 8 shows photos of the sectioned cups for formulations B1 & R1 both with 10% BaSO4, and B3 & R3 without BaSO4 additions. There is very little adherence of aluminium to the samples made with R50, and where it does exist, only very thin layers can be seen. More significantly, whilst sample B3 clearly shows areas of aluminium metal penetration into the refractory, there is no recognisable infiltration into the microstructure of sample R3. This correlates with the lower apparent porosity results of all the R50 samples as shown in Fig. 4. The chemical bonding of the R50 aggregate to the matrix, and the reduced casting water demand due to the fused nature of the R50 aggregate ensure the low porosity of the R50-based formulations. This, in turn, significantly enhances the penetration and corrosion resistance.
B1: Bauxite (10% BaSO4) B3: Bauxite (0% BaSO4)
R1: R50 (10% BaSO4) R3: R50 (0% BaSO4)
Fig. 7 : Alcoa cup tests after heating to 800°C for 72 hours.
A final, but significant, consideration is that BaSO4 starts to decompose at 1200°C which leads to a massive volume expansion around 1400°C, as seen in Fig. 8 for the bauxite-based formulations (B1 & B2). In the case of R50, how-ever, since significantly less BaSO4 needs to be added to maintain the infiltration resistance of the castable, the associated advantages of a higher service temperature can be realised. Consequently, using R50 as the aggregate gives supplementary security even if unexpect-edly high temperatures occur during aluminium production.
Fig. 8 : Permanent linear change after firing at 1400°C vs open porosity for R50 (R1-R3) and bauxite (B1-B3).
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Penetration
Technical Paper Reference : TP-GB-RE-LAF-097
4 Experimental Procedure4.1 Material Details : Calcuim Magnesium Aluminate (CMA) binder Castable developments for steel ladles during the last three decades have shown alumina-spinel and alumina-magnesia systems to be most effective[3-5]. More recently, hybrid systems which combine both materials have been developed[6]. Kantani and Imaiida[7]
found that the best compromise between slag penetration and corrosion resistance could be achieved when the castable contains 20 - 40% magnesium aluminate spinel after firing. It has also been shown that the slag penetration can be minimized by reducing the spinel grain size [8]. Very fine spinel can be created by adding magnesia to the castable, which reacts during firing with the alumina fillers to form spinel insitu. However, the magnesia addition often has negative side effects, creating problems during dry-out due to the magnesia hydration and volume expansion at firing temperatures due to the spinel formation. To improve the volume stability of the castable, small amounts of microsilica are often added to the dry-mix which creates a small amount of liquid phase during firing. Although this counteracts the expansion caused by the spinel formation[5, 9, 10]. Development work on a composite hydraulic binder (calcium-magnesium-aluminate cement) which would combine micro-crystalline spinel (MA) with calcium aluminate phases (CA, CA2) has been the centre of numerous patents and publications since 1969 (Patent no 1575633, Romania)[11]. Numerous publications were lodged in the late 1990’s by predominantly Japanese (1996)[12], Spanish (1999)[13], and Chinese[14] authors. Kerneos lodged a unique patent in 1999[15] to produce a commercially and industrially viable calcium magnesium aluminate (CMA) binder for steel ladle applications. This new CMA 72 has been successfully produced
on an industrial scale. The raw material mix is sintered in a rotary kiln to simultaneously form a micro-crystalline spinel together with calcium aluminate phases within the same clinker. This can be achieved below the sintering temperature of pure spinel and with crystal sizes as small as spinel that is generated in-situ inside the matrix of an alumina-magnesia castable.
CA2
CA
CA2
CAMA
MA
MA
CA
CA
MA
MACAC grain CMA grain
Fig. 9 : Schematic microstructure of a CAC and a CMA grain (average grain diameter ca. 15µm).
The exact chemical and mineralogical comparison between SECAR® 71 and CMA can be found in Tab. 10. Both products contain 70% Al2O3 but CMA contains only 10% CaO and 20% MgO, the latter facilitating the presence of the MA phase in the CMA. CMA clinker displays a unique microstructure resulting from the intergrowth of the hydraulic phases calcium mono-aluminate (CA) and calcium di-aluminate (CA2) with MA phases during clinker formation in the rotary kiln (Fig. 9). The hydraulic properties of this new CMA cement are described by Assis et al.[16]. Both binders have been ground to a specific surface area of approx. 4000cm2/g (Blaine) with a median grain size d50 for both cements of about 15µm.
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Table 10 : Chemical and mineralogical compositions.
Chemistry Al2O3 CaO MgO SiO2
SECAR® 71 68.7-70.5 28.5-30.5 <0.5 0.2-0.6
CMA 72 69-71 8-11 16-22 <1.0
Mineralogy CA CA2 MA C2ASSECAR® 71 56-61 39-44 0 <1
CMA 72 18-22 8-12 68-72 <1
4.2 Test Methods : CMA TestingThis study specifically focuses on the wear resistance of alumina-spinel and alumina-magnesia ladle castables and their properties at high temperatures. The various formulations that have been tested are given in Tab. 11. Both systems have been formulated with pure calcium aluminate cement (SECAR® 71) as the reference and with the new CMA cement. The formulations MA1 and MA2 use pre-reacted sintered spinel. Castables M1 and M2 contain free sintered MgO (Periclase) which reacts to form spinel in-situ during castable firing. Castables MA1 and M1 use SECAR® 71 as the binder while MA2 and M2 apply the new CMA 72 binder. The formulation logic was to maintain the chemical composition of the castable and the same total MA phase after sintering. The total amount of binder has been chosen to ensure that all 4 castables are low cement castables (LCC) with a constant CaO content of 1.7%.
Table 11 : Alumina-spinel (MA) and alumina-magnesia (M) model castables with CA and with CMA cement.Castable MA1 MA2 M1 M2Binder system CAC CMA CAC CMA
Tabular Alumina 0-6 mm 60 61 75.5 70
Reactive Alumina 11 11 11 8
Sintered Spinel 0-1 mm 13 10
Sintered Spinel <90 µm 10
Sintered MgO <74 µm 6.5 3
CAC (SECAR® 71) 6 6
CMA (CMA 72) 18 18
Silica (Elkem 971 U) 1 1
Peramin® AL200 +0.1 +0.1 +0.15 +0.1
Water +4 +4 +4.5 +4.5
A polycarboxylate ether (Peramin® AL200) has been chosen to efficiently deflocculate the castables at a very low amount of mixing water. Both the amount of water and the Peramin®
AL200 have been adjusted in order to achieve the same initial fluidity for all 4 formulations.
The permanent linear change has been measured after firing samples for 3h at the indicated test temperature. Hot modulus of rupture has been determined according to European standard EN 993-7. Dried samples have been heated up to the test temperature at 5 K/min and then held for 30 min at the test temperature prior to the hot modulus measurement. All additional thermo-physical properties have been studied using cylindrical samples dried at 110°C in the test furnace as specified in EN 993-8. To measure the thermal expansion, the samples have been heated up to 1550°C with a load of 0.05 MPa and kept at 1550°C for 1h before being cooled down to 1000°C. Then, at 1000°C a load of 0.2 MPa has been applied and the samples heated up again in order to study the refractoriness under load.
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The corrosion and penetration resistance against different slag compositions was tested in a laboratory scale rotary kiln according to ASTM C874-99. Here, the test specimens were prepared using a bigger mixer than those for the physical property tests. The higher mixing energy of the larger mixer allowed a further reduction of water. The water was reduced to 3.9% for the alumina-spinel castables (MA) and to 4.0% for the alumina-magnesia formulations (M). The vibrated samples were cured at 20°C for 24h, dried at 110°C, and then pre-fired to 1550°C for 5h. The specimens were installed in the pilot rotary kiln where they were heated up to 1550°C again and kept at this temperature for 30 minutes prior to the first addition of 900g of slag. 1.7kg/h of fresh slag was introduced into the kiln during the following 5h at 1550°C.
The furnace rotated at a constant speed of 2½ rpm. The furnace was tilted 3º axially towards an oxy-acetylene flame burner at the lower end of the kiln. The slag pellets were charged into the upper end of the tilted rotary kiln. In this way, the molten slag washed over the lining, finally dripping off at the lower end of the kiln. Two different slag compositions were used (Tab. 12). The dimensions of the castable specimens were measured before and after the test to quantify the degree of wear.
Corrosion tests were also conducted in a laboratory induction furnace. Samples of the test formulations lined the wall of the induction furnace which was charged with steel and covered with one of the slags (composition in Tab. 12). The test temperature was 1600°C. The steel contained 0.08% C, 1.9% Si, 0.3% Mn, 0.01% S, and 0.02% P. The wear was quantified by determining the ratio between the original cross sectional area of the specimens and the cross sectional area remaining after the test. The areas were measured using image analyzing software. Furthermore, SEM techniques were used to study the microstructure of the castables and to quantify the depth of penetration of the slag.
5 Experimental Results & Discussion5.1 Thermo-physical castable propertiesThe difference between the castables with pre-formed spinel (MA1, MA2) and those with in-situ spinel formation (M1, M2) can easily be seen in Fig. 13.
While both MA1 and MA2 keep high volume stability, those with free MgO (namely M1 & M2) show a significant permanent linear change after firing to 1550°C due to the in-situ spinel formation. However, mix M2, which contains less free MgO than M1, shows lower expansion.
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Fig. 13 : Permanent linear change of castables.
The measurement of the thermo-physical properties (Fig. 14) also indicates that the permanent expansion with M2 is lower than with M1 when a load of only 0.05 MPa is applied on the sample during the first heat-up and during 1h soaking at 1550°C followed by cooling to 1000°C.
After this pre-firing procedure, the application of a load of 0.2 MPa results in an excellent refractoriness under load with a T2 of 1680°C for the CMA containing M2. While the silica free castables MA1 and MA2 show very high hot modulus of rupture (HMOR), the values are quite low in the case of M1 and M2 at 1350°C and 1550°C respectively (Fig. 15) due to the silica content. However, the lower permanent expansion of M2 and the presence of the microcrystalline spinel in CMA indicate that an optimization step of this formulation with respect to silica and periclase content could improve the hot properties of this formulation.
Fig. 14 : Thermo-physical properties of model castable M1 (SECAR® 71) and M2 (CMA 72).
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5.2 Castable microstructureSEM micrographs of polished matrix samples fired at 1550°C are shown in Fig. 16. These matrix samples were derived from the castable formulations given in Tab. 11 after the removal of any aggregate coarser than 300µm. The micrographs clearly show that the pores in the CAC containing matrices are significantly larger than the pores in the CMA 72 containing matrices.
0
5
10
15
20
25
30
1000 1350 1550Temperature (°C)
HM
OR
(MPa
)
MA1 (CAC) MA2 (CMA) M1 (CAC) M2 (CMA)
Fig. 15 : Hot modulus of rupture of model castables.
Furthermore, in the latter case, the micro-crystalline phases of spinel and calcium aluminate are more homogeneously distributed. For the CAC matrices, a certain area in the microstructure is occupied by calcium aluminates alone, but the corresponding area is occupied by ultra-fine spinel and calcium aluminate phases in the CMA 72 containing matrices.
MMMAAA222 (((CCCMMMAAA 777222)))
100 µm
Fig. 16 : Matrix microstructure of model castables with Secar 71 and CMA 72 (1550°C, 3h).
5.3 Thermo-chemical castable properties The following results show quite clearly that the CMA 72 containing castables achieve both better corrosion and penetration resistance to the slag chemistries tested. In the induction furnace, the corrosion of the CMA containing mixes was around 50% lower than the CAC containing reference mixes. The castables based on CMA 72 resisted both of the slags tested better than the CAC containing formulations (Fig. 17). A similar trend can be seen in the results from the rotary kiln tests where an improvement in the range of 20% was measured between the MA1 and MA2 samples, and again between the M1 and M2 formulation samples (Fig. 18). In all cases, the iron oxide rich slag B caused more corrosion than slag A. CMA-based castable M2 showed the highest resistance to wear and the lowest corrosion with the typical ladle slag A. Slag penetration was lowest in the MA2 castable, even with the iron rich slag B (Fig. 19).
This improved resistance to slag penetration could be significant for functional pre-cast products where adhering slag and steel is often cleaned from the working surface by oxygen lance. This cleaning method creates very aggressive iron-rich slags which could be resisted more effectively by CMA containing formulations.
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MMMAAA111 (((SSSeeecccaaarrr 777111)))
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02468
10121416
MA1 (CAC) MA2 (CMA) M1 (CAC) M2 (CMA)
Cor
rode
d cr
oss
sect
ion
area
(%) Slag B Slag A
Fig. 17 : Corrosion of the model castables in a laboratory scale induction furnace with the two slag compositions.
02468
10121416
MA1 (CAC) MA2 (CMA) M1 (CAC) M2 (CMA)
Wea
r (m
m)
Slag B Slag A
Fig. 18 : Corrosion of the model castables in laboratory scale rotary kiln with the two slag compositions.
0
200
400
600
800
1000
MA1 (CAC) MA2 (CMA) M1 (CAC) M2 (CMA)
Pene
trat
ion
(µm
)
Slag B Slag A
Fig. 19 : Slag penetration of model castables in laboratory rotary kiln.
6 Conclusions Novel calcium aluminate containing products can not only provide the binder function but also add to and enhance the final refractory performance as measured by corrosion resistance.
The fused calcium aluminate aggregate, R50, displays enhanced bonding properties due to the physical and chemical bonds formed between the refractory matrix and the reactive surface of the R50 aggregate. When applied in microsilica-free medium cement castables for aluminium applications, R50 facilitates new formulation options to improve the operating temperature resistance. Compared with the traditional bauxite-based MCC containing barium sulphate, the R50-based formulation without the anti-wetting agent displays equivalent infiltration and corrosion resistance but provides increased thermal stability and lining integrity up to 1350°C.
CMA, the new calcium magnesium aluminate cement significantly improves the corrosion and penetration resistance of monolithics for steel ladle applications. This is based on the innovative microstructure of CMA which provides micro-crystalline spinel within the matrix, minimising the pore size and improving penetration resistance. Homogeneous distribution of the microcrystalline spinel within the castable matrix enhances the in-situ life of both spinel containing and spinel-forming castables.
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7 AcknowledgementsWe would like to thank the Kerneos laboratories in France and China, the Wuhan University of Science and Technology, China, the ITMA institute, Spain, the ICAR institute, France, and the BCMC institute, Belgium, for the support of this study.
8 References
[1] C. Wöhrmeyer, C. Parr, H. Fryda, E. Frier: Stronger bonds for monolithic castables through surface reactive calcium aluminate aggregates. Aachen congress, Germany, (2010).
[2] C. Wöhrmeyer, N. Kreuels, C. Parr, T. Bier: The use of calcium aluminate solutions in the aluminium industry. Unitecr congress, Berlin, (1999).
[3] T. Yamamura et al.: Development of alumina-spinel castables for steel ladles. Taikabutsu 42, 8 pp 427-434 (1990).
[4] S. Asano et al.: Mechanism of slag penetration in alumina-spinel castable for steel ladle: Taikabutsu 43, 4, pp 193-199 (1991).
[5] H. Naaby, O. Abbildgaard, G. Stallmann, C. Wöhrmeyer and J. Meidell: Refractory wear mechanisms and influence on metallurgy, 37th Int. Colloquium on Refractories, Aachen, Germany, pp. 198-204 (1994).
[6] K.H. Dott: Monolithic ladle lining at SSAB Tunnplåt in Luleå, Sweden. RHI Bulletin, 1, pp 34-37 (2008).
[7] T. Kanatani, Y. Imaiida : Application of an alumina-spinel castable to the teeming ladle for stainless steelmaking. UNITECR’93, pp 1255-1266, (1993).
[8] M. Nakashima, T. Isobe, S. Itose: Improvement in corrosion of alumina-spinel castable by adding ultra fine spinel powder. Taikabutsu, 52,2, pp 65-72, (2000).
[9] T. Bier, C. Parr, C. Revais, M. Vialle : Spinel forming castables : Physical and chemical mechanisms during drying. Refractories Application 4, pp 3-4, (2000).
[10] Y.C. Ko: Development and production of Al2O3-MgO and AlsO3-spinel castables for steel ladles. Mining and Metallurgy, Taipei, 47, 1, pp 132-140.
[11] A. Braniski, T. Jonescu, N. Deica, Patent (PV no. 145.441, No 1575633), Romania.
[12] Y. Koya, Y. Sasagawa, Denki Kagaku Kôgyô Ltd., Patent (HEI 8-198649), Japan.
[13] A.H. De Aza, P. Pena, S. De Aza: Ternary system Al2O3-MgO-CaO: Paper I, J. Am Ceram Soc., Vol 82 [8], (1999).
[14] D. Feng, et al.: Preparation & application of aluminate cements containing magnesia-alumina spinel, J. Naihuo Cailiao 41(1), (2007).
[15] J.P. Falaschi et al. : Liant du type clinker, utilisation et procede de fabrication d’un tel liant. Demand de brevet d’invention, FR2788762A1, (1999).
[16] G. Assis et al.: Castables with improved corrosion resistance for steel making applications, Unitecr’11, (2011).
[17] C. Wörhmeyer et al.: New spinel containing calcium aluminate cement for corrosion resistant castables, Unitecr’11, (2011).
