Alinite — Chemical composition, solid solution and hydration behaviour

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CementandConcreteResearch, Vol. 24, No. 8, pp. 1413-1422,1994 i!iiiiiiiiiiiiiiiiiiiiiI Copyright© 1994 ElseviefScience Ltd iiiiiiiiiiiiiiiiiiiiiiii Printed intheUSA. Allrightsreserved iiiiiiiili!iiiiiiiiiiiii

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ALINITE - CHEMICAL COMPOSITION, SOLID SOLUTION AND H Y D R A T I O N BEHAVIOUR J. Neubauer and H. POllmann Mineralogical Institute, University of Erlangen, Germany Schlol~,garten 5a, 91054 Erlangen (Communicated by F.W. Locher) (Received January 7, 1994)

ABSTRACT The chemical composition of alinite was investigated in the system CaO SiO2- AI20 3 - MgO - CaCI 2. Solid solution was observed. The formula should be written as Ca 10Mgl.x/2Dx/2[(SiO4)3+x(AIO4)l.x/O2/CI] with 0.35
INTRODUCTION Since the late 70th soviet scientists were engaged in manufacturing low temperature clinkers. ([1], [2], [3]). Because of the addition of CaCI 2 to a normal Portland cement raw mix it could be managed to decrease the burning temperature from 1450°C to 1100*C. The cement clinker contains as main constituent chloride bearing alinite in spite of alite in ordinary Portland cement. The hydraulic properties of alinite were as good as the properties of alite ([4], [5]). Since the 80th about 100 000 t/a alinite cement were produced in the former Soviet Union. Since the early 80th also scientists in India ([6], [7]) investigate possibilities to manufacture low temperature clinkers. In Germany [8] investigated the synthesis of calcium silicates at low temperatures. In 1989 [9] carried out experiments to produce alinite cement from calcium-based scrubber waste. The following tables 1 and 2 summarize chemical composition and crystallographic data determined by different authors (I-I means a lattice vacancy). Own investigations should proof the chemical composition of alinite in the system CaO - SiO2- AI20 3 MgO - CaCI 2. 1413

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J. Neubauer and H. P6llman

V~]. 24, No. 8

Table 1 Chemical composition of alinite by different authors author

formula

[5] [1] [10] [11] [2]

3(CaO0.875MgO0.070CaCI2 0.055)(SIO2 0.885 AI203 0.115) Ca11 (Si0.75AI0.25)4018CI Ca9.9Mg0.8[-]0.3[( SIO4)3.4(A104)0.6/01.9/CI] Ca 10Mgl _zFIz[(SiO4)3+x(AIO4)l _x/O2_y/CI] with (y=z+x/2) Ca11 (Si,AI)4018CI

Table 2 Chemical and crystallographic data of alinite by different authors author mol Si/AI mol MgO* SG ao (A) Co (A)

[5] 3.87 0.75

[1 ] 3

[10] 5.67 0.8

[11 ] 5.9-8.5 0.52-0.86

P4/nnc

1~,2m 10.471 8.617

IZl2m 10.451 8.582

10.479 8.598

[2]

1~,2m 10.471 8.614

"related to 10 mol CaO

METHODS All syntheses were made from pure components using the following reagent grade chemicals: • Oxides: CaO, MgO, c~-SiO2, 3,-AI203 • Chlorides: CaCI2-2H20 All mixtures were pulverized and pre-dried at 200°C. Syntheses were made at a temperature of 1100°C. The experimental difficulties vaporisation and sublimation of CaCI2 can be decreased by the following experimental arrangement: Two platinum crucibles are put into each other. The inner and the outer one contain the same homogenized mixture. The weight of the outer powder has to be three or four times the mixture of the inner one. Each crucible is sealed by a platinum lid. The CI2partial pressure in the interstice is corresponding with the stable phases. The loss of CI- is compensated by the material in the outer crucible. Normally equilibrium is reached after 3 h burning with two homogenisation steps. Small amounts of free CaCI2 (Chloride not combined with alinite) could not be avoided completely. The pure phase was investigated by XRD powder method. The indexing and the refined lattice parameters a r e given in the appendix. All other samples ware also characterized by XRD powder methods. The lattice parameters of alinite were refined by least squares method. All synthesis containing pure alinite (without additional phases) were additionally investigated by DCA with a custom made high sensitive calorimeter ([12]). The samples were ground to a specific surface of 3000 cm2/g (Blaine). Free chloride could be removed by washing the samples with methanol. All hydration products were investigated by SEM and XRD.

i !i:!!!~::,iii~ii!!~! i!iiiii~iiiii!ii!::i:i~i VoL24, No. 8

COMPOSITION. SOLID SOLUTION, HYDRATION

~4~5

RESULTS

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I. Composition of alinite 1.1 Variable content of MgO in alinite with chemical composition after [11] The formula after [11] is Ca 10Mgl_zl-lz[(SiO4)3+x(AIO4)l _x/O2.y/CI] with y=z+x/2. The molar ratio of Si/AI should be between 5.9 and 8.5, the MgO coritent between 0.52 and o. 86. Own investigations fixed the molar ratio of Si/AI to 7. This means the value of x is 0.5. The MgO content varies from 0.25 to 1 mol, the values of z between 0.75 and 0. Table 3 shows the chemical composition, additional phases and lattice parameters of alinites. Table 3 Chemical and crystallographical data of alinite synthesis by variable MgO content mol MgO Si/AI (mol) AI20 3 (wt%) SiO2 (wt.%) MgO (wt.%) phase distribution

ao (A) co (A) SG ,

H,,

0.25 7 3.0 24,4 1.1 alinite CaO C2S C11A7.CaCI2 10.470 8.615

0.50 7 3.0 24.5 2.4 alinite CaO C2S

0.75 7 3.0 24.6 3.4 alinite CaO C2S

1.00 7 3.0 24.7 4.7 alinite C2S

10.471 8.616

10.453 8.580

10.451 8.583

1~,2m

1~,2m

1~,2m

1~,2m

,,,H,

Variable lattice parameters ao and co gave rise to a solid solution of alinite. Additional phases covering the whole investigated area seem to exclude the proposed formula after [11].

1.2 Variable content of Si4+ and AI 3+ in alinite with chemical composition after [11] Charge compensation for the replacement of Si4+ by AI3+ is attained by oxygen vacancies. The MgO content for the following investigations was constant with the value 0.75 mol. X varies between 0.3 and 0.5, that means a molar ratio of Si/AI between 4.3 and 67. Table 4 shows the chemical composition, additional phases and lattice parameters of alinites. Variable lattice parameters ao and co again gave notice of a solid solution of alinite. Additional phases over the whole investigated area with the exception of one synthesis show that the formula proposed by [11] could not be confirmed.

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J. Neubauer and H. Ptillman

Vol. 24. No. 8

Table 4 Chemical and crystallographical data of alinite synthesis by replacement of Si 4+ by AI 3+ mol MgO Si/AI (mol) AI20 3 (wt.%) SiO 2 (wt.%) MgO (wt.%) phase distribution

ao(A) co(A )

0.75 3.3/0.7 4.71 4.2 23.3 3.5 alinite CaO C2 S C 11A7-CaCI 2 10.470 8.615

0.75 3.35/0.65 5.15 3.9 23.6 3.5 alinite CaO C2S

0.75 3.4/0.6 5.67 3.6 23.9 3.5 alinite C2S

10.472 8.616

10.468 8.609

10.457 8.590

10.450 8.582

1~,2m

1~,2m

1~,2m

1~,2m

IT42m

SG

0.75 3.45•0.55 6.27 3.3 24.3 3.5 alinite

0.75 3.5/0.5 7 3.0 24.6 3.4 alinite C2S CaO

1.3 Replacement of Si 4+ and [] by AI 3+ and 1/2 Mg 2+. A possible formula which could give the composition of alinite and its solid solution could be Cal0Mgl_x/2CIx/2[(SiO4)3+x(AIO4)l_x/O2/CI]. For investigations in this case values for x between 0.5 and 0.3 are chosen. The Si/AI ratio differs between 4.71 and 7. Table 5 shows the chemical composition, additional phases and lattice parameters of alinite synthesis. The lattice parameters a o and c o of alinite are shown in Figures 1 and 2. From Si/AI mol ratio 5.15 to 6.27 lattice parameters of alinite show a nearly linear shift with the chemical composition. No additional phases appear. This shows the possibility of the replacement of Si4+ and [] by AI3+ and l/2Mg 2+. The formula of Alinite is: Ca10Mgl -x/2Dx/2[(SiO4)3+x(AIO4)1 -x/O2/CI] with 0.35
ao i n A 10.475

10.470

8.610

10.465

10.460

alinite ss + additional phases

alinite ss + addi~onal phases

8.600.

alinite ss + additional phases

alinite ss + additional phases

8.590. 10.455

10.450 4.00

I 5.00

I 6.00 mol Si/AI

J

I 7.00

8.~

4.~

7.~ tool Si/AI

Figures 1 and 2 Variation of the lattice parameter ao and co of alinite. Replacement of Si4+ and [] by AI3+ and 1/2 Mg2+

8.~

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~ii!ii'~~,,iiiiiii Vol. 24, No. 8

ALINITE, COMPOSITION,SOLID SOLUTION, HYDRATION

1417

Table 5 Chemical and crystallographical data of alinite synthesis by replacement of Si4+ and [] by AI3+ and 1/2 Mg:~+ tool MgO Si/AI (mol) AI20 3 (wt.%) SiO2 (wt.%) MgO (wt.%) phase distribution ao(A)

co(A)

0.85 3.3•0.7 4.71 4.2 23.2 4.0 alinite C11A7-CaCI2

0.825 3.35•0.65 5.15 3.9 23.5 3.9 alinite

10.471 8.616

10.472 8.615

IT42m

1~,2m

SG

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0.8 0.775 0.75 3.4•0.6 3.4510.55 3.5•0.5 !i i i i i ! !i! i i i 5.67 6.27 7 3.6 3.3 3.0 23.9 24.2 24.6 3.8 3.7 3.5 iiii!il~,~iiiiii!! alinite alinite alinite C2S CaO 10.463 1 0 . 4 5 1 10.453 8.595 8.583 8.581 142m

IT42m

1~,2m

Solid solution occurs between: Ca10Mg0.775i-10.225[(SiO4)3.45(A104)0.55/02/CI] Ca10Mg0.825D0.175[(Si04)3.35(A104)0.65/02/CI] A summary of X-ray data of alinite with the composition Cal0Mg0.sD0.2 [(SIO4)3.4(A104)0.6/02/CI] is given in the appendix.

II. Hydration behaviour of alinite Reactions from alinite with water were described by [13], [14] and [5]. To investigate the hydration behaviour of alinite in relation to the chemical composition three samples of different chemical composition were synthesized under identical conditions. The chemical compositions were CalOMgl.x/21-1xl2[(SiO4)3+xl(AlO4)l_xl021CI] with x = 0.35, 0.40 and 0.45. The identical synthesis parameters lead to equal amounts of free chloride.

I1.1 Calorimetric investigations According to [4] and [13] a decreasing Si/AI mol ratio increases the hydraulic activity of alinite. This could not be corroborated. The heat flow of alinites with Si/AI mol ratios of 5.15, 5.67 and 6.27 (x = 0.35, 0.40 and 0.45) is shown in Figure 3. The water/cement ratio was 1. The hydration behaviour of alinites with different Si/AI ratio show no significant differences. A second investigation of alinites with equal Si/AI ratio but different free chloride content shows the strong influence on the hydration behaviour (Figure 4). Small amounts of free chloride accelerate the reaction to a high degree so that differences because of different Si/AI ratio could not be detected.

1418

J.Neubauer and H.P611man h e a t f l o w in

Vol.24,No.8

mW - _ _

alinite alinite alinite

x = 0.35 x = 0.40 x = 0.45

2O

15-

10-

5-

O-

~

[

0

~ "

120

I

240

'

I

.360

'

l

I

480

600

I

I

720

'

l

840

'

960

I

10'80 1 2 0 0

t in m i n

Figure 3 Heat flow of alinites of different composition with x = 0.35, 0,40 and 0.45 at 22°C. h e a t f l o w in

mW

25-

__ -

20-

-

alinite x = 0 4 with 0.5 % CaCI2 x = 0.4 with 0.25 % CaCI2 a l i n i t e x = 0.4 alinite

15-~\ 10/

0

0

~\,,.

' 1 ; ) 0 ' 24"0' 3 6 0 ' 4 8 0 ' 6 ( ) 0 ' 7½0' 84"0 ' 9~)0'10180'1200 t in m i n

Figure 4

Heat flow of alinites of same composition with x = 0.40 and different free chloride at 22°C.

11.2 XRD analysis of alinite hydration products Alinite with x = 0.4 and a specific surface of 3000 g/cm 2 (Blaine) was shaken in a polyethylene bottle with a waterlcement ratio of 10. After 72 hours the suspension was filtered and examined at 100% rel. humidity by XRD. The following phases could be detected: Ca(OH)2 (portlandite) C3A. CaY 2-10H20 unhydrated alinite

Vol. 24, No. 8

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ALINITE, COMIPO$1TION,SOLID SOLLFI'ION,HYDRATION

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The composition of C3A.CaY2-10H20 differs from pure Friedel's Salt (C3A.CaCI2.10H20). Up to 15 mol% CaCI2 is replaced by Ca(OH)2 respectively CaCO3 (contamination by CO2 from the air) [15]. The general formula is C3A. (1-x-y)CaY 2 - (x)CaCO 3 • (y)Ca(OH) 2 • 10H20. ll.3 SEM Investigations

Examinations by SEM (Figures 5 and 6) of hydrated samples show some amorphous i~iiii!~!~!i CSH-gel in addition to Ca(OH)2, C3A.CaY2.10H20 and alinite.

.¢v l.~m

Figure 5 Alinite covered with portlandite and lamellar calciumaluminatehydroxy salts

~ v v

jl,mlml~I

Figure 6 Hydrated alinite after 72h: Portlandite, CSH-gel and unhydrated alinite

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J. Neubauer and H. P611man

Vol. 24, No. 8

Microprobe analysis of the CSH-gel did not give indications for the incorporation of CIin the CSH-phases. CONCLUSION

A summary of crystallographical and chemical data of alinite examined by different authors in comparison to these results can be seen in table 6 and 7. Diadochic substitution of other ions were investigated by [11]. A replacement of CI- by Br- [16] and F[17] seems to be possible. Table 6 Chemical composition of alinite by different authors author

formula

[5] [1] [lO] [11]

3(CaO0.875MgO0.070CaCI2 0.055)(Si02 0.885 AI203 0.115) Ca11 (Si0.75AI0.25)4018 CI Ca9.9Mg0.81-10.3[(SiO4)3.4(AI04)0.6/01.9/CI] Ca 10Mgl _zl3z[(SiO4)3+x(AlO4)l_x/O2_y/CI] with (y=z+x/2) Ca11 (Si,AI)4018 CI Cal0Mgl -x/21-Ix/2[(SiO4)3+x(AlO4)l-xl021CI] with 0.35
[2] this paper

Table 7 Chemical and crystallographic data of alinite by different authors author Mol Si/AI Mol MgO* SG ao (A) co (A)

[5] 3.87 0.75

[1 ] 3 -

P4/nnc -

1~,2m 10.471 8.617

-

[10] 5.67 0.8 1~,2m 10.451 8.582

[11 ] 5.9-8.5 0.52-0.86 10.479 8.598

[2] -

this paper 5.15-6.27 0.775-0.825

13,2m 1~,2m 1 0 . 4 7 1 10.472-10.451 8.614 8.583-8.615

"related to 10 Mol CaO

The equation for the hydration of alinite after 72 h could be written as follows: I

II

I

I alinite + nH20--, C3A.CaCI2.10H20 + Ca(OH)2, + CSH(CI?)-gel + unhydrated,, alinite I

(Reaction stopped after 72 hours, Y= 112 CO32-, 2(OH)-, 2CI-) By means of these investigations the complex chemical composition of alinite could be established. Alinite seems to be formed very well in "dirty systems" containig different elements. It is not stable in a system CaO - SiO2 - AI20 3 - CaCI 2. The properties of different solid solutions do not vary significantly. Normally additional phases (especially free CaCI2) are covering drastically the hydration behaviour. In these cases a strong acceleration occurs. This is important for application purposes.

i !!ii ALINTrE,COMPOSrrION, SOLIDSOLUTION, HYDRATION

Vol. 24, No. 8

1421

:ii:

ACKNOWLEDGEMENTS

)) :) :::::::::::::: : : :21:111:::

The authors which to thank the Deutsche Forschungsgemeinschaft for financial sup-

REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

:::::

V.V Ilyukhin, N.N. Nevsky and M.J. Bikbaou, Nature 269, 397 (1977) B Noudelman, M. Bikbaou, A. Sventsitski and V. Ilyukhin, 7th international congress on the chemistry of cement (Paris) 3, 169 (1980) M. Bikbaou, 7th international congress on the chemistry of cement (Paris) T h e m e V, 205 (1980) F. yon Lampe and G. Oliev, Silikattechnik 11 379, (1988) F. Massazza and C. Gilioli, II Cemento 2, 101 (1983) R.K Agarwal, S.V. Paralkar and A.K. Chatterjee, 8th international congress on the chemistry of cement (Rio de Janeiro) Communications, Theme I, Volume 2, 327 (1986) EC. Subbarao, P.C. Kapur and N.R. Jagannathan, Mater. Res. Bull. 22, 8, 1055 (1987) D. B0rger and U. Ludwig, 8th international congress on the chemistry of cement (Rio de Janeiro) Communications, Theme I, Volume 2, 372 (1986) R. Oberste-Padtberg and J. Neubauer, Wasser, Luft und Boden 10, 62 (1989) F. von Lampe, W. Hilmer and K.H. Jost, Cem. Congr. Res 16, 505 (1986) F. von Lampe, Silikattechnik 6, 194 (1988) H.-J. Kuzel, TIZ-Fachberichte 108, 46 (1984) F. yon Lampe, G. Oliev and A.I. Domanskij, Baustoffindustrie 1, 10 (1989) A.I. Boikova, L.V. Grishchenko and A.I. Domanskij, 8th international congress on the chemistry of cement (Rio de Janeiro) 3, 271 (1986) H. P011mann, 8th international congress on the chemistry of cement (Rio de Janeito) Theme 2, Volume 3 (1986) W. Kurdowski, Cem. Con. Res. 17, 361 (1987) U. Ludwig and L. Urbonas, ZKG 9, 568 (1993)

APPENDIX Ca4nMgn 11-1o_2[(SiO4)_~4/(AIO4)n n/O~/Cl]

an=bn: 10.463A 2eExp (Cu Ka) (Degrees)

Cn: 8.595A Int. 1/1100

Z=2 d (A)

V= 941.0A3 h k I

RG:T? APO (Degrees)

11.96

2

7.393

1

1

0

+.008

13.30

3

6.651

1

0

1

16.94 21.60 24.02

2 5 2

5.229 4.111 3.702

2 2 2

0 1 2

0 1 0

-.020 +.007 -.005

-.016

i

........

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J. Neubauer and H. POllman

Vol. 24, No. 8

CalOMgn Rl-ln ~[(Si04)~ •l(AlO•)n K/O~/Cl] (continued) an=bn: 10.463 A 2 e E x p (Cu Kc0 (Degrees)

co: 8.595 A Int. I/I 100

26.92 4 27.57 27 31.91 100 32.55 12 34.16 32 36.41 4 36.76 7 36.89 7 38.45 8 40.33 5 40.73 6 42.02 16 43.83 3 44.07 3 44.51 5 45,60 2 47.97 8 49,22 20 50.61 3 50.85 2 52.41 6 53.91 3 54.22 3 54.33 8 55.26 9 55.45 8 57.03 4 57.25 9 57.35 4 58.25 2 59.84 10 63.08 4 65.84 2 66.80 5 68.21 2 71.08 2 72.17 4 73.77 2 75.99 1 Philips diffractometer, intensities 1/2 °, 1 ° und

Z =2

V = 941.0 A 3

d (A) 3.309 3,233 2,802 2.748 2.623 2.465 2.443 2.434 2.339 2.234 2.213 2.148 2.064 2.053 2.034 1.988 1.895 1.850 1.802 1.794 1.744 1.699 1.690 1.687 1.661 1.656 1,613 1.608 1.605 1.582 1.544 1.473 1.417 1.399 1 374 1.3251 1.3078 1.2833 1.2512 4 ° divergency slit

RG: T?

h

k

I

~.O (Degrees)

3 3 2 3 3 3 2 4 4 4 3 0 1 5 5 2 5 4 3 5 6 4 4 6 4 5 2 5 5 4 6 7 7 5 7 7 8 7 8

1 0 2 2 1 3 1 1 2 0 0 0 1 1 0 0 2 4 1 3 0 4 3 1 0 3 1 2 4 2 2 0 2 5 3 0 0 4 0

0 1 2 1 2 0 3 1 0 2 3 4 4 0 1 4 1 0 4 0 0 2 3 1 4 2 5 3 1 4 2 1 1 2 0 3 0 1 2

-.003 -.007 +.018 +.012 -.011 +.011 +.010 -.010 +.007 +.000 +.009 +.009 -.005 -.024 -.013 +.000 +.008 +.001 +.002 +O10

-.014 -.010 -.014 -.015 -.018 +.008 +.005 +.010 +.003 +002 -.014 +.006 +.013 -.008 + 009 +.006 +.008 -.004 -.008