Development of pore solution chemistry and hydrate assemblages - - PowerPoint PPT Presentation

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Development of pore solution chemistry and hydrate assemblages - - PowerPoint PPT Presentation

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Development of pore solution chemistry and hydrate assemblages during hydration of calcium sulfoaluminate cements Frank Winnefeld, Barbara Lothenbach, Mohsen Ben-Haha Swiss Federal Laboratories for Materials Testing and Research

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SLIDE 1

Development of pore solution chemistry and hydrate assemblages during hydration

  • f calcium sulfoaluminate cements

Frank Winnefeld, Barbara Lothenbach, Mohsen Ben-Haha Swiss Federal Laboratories for Materials Testing and Research Concrete/Construction Chemisty Lab Dübendorf, Switzerland

Materials Science & Technology

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SLIDE 2

Outline

Introduction Used cements Hydration of calcium sulfoaluminate cements

  • Isothermal heat flow calorimetry
  • X-ray diffraction analysis
  • Thermogravimetric analysis
  • Pore solution chemistry
  • Microstructure (SEM)
  • Thermodynamic modelling

Conclusions

2

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SLIDE 3

Comparison OPC - CSA

OPC CSA main phases * C3S, C2S, C3A, C4AF C4A3s (= ye‘elimite) raw materials limestone & clay limestone, bauxite & anhydrite burning temperature ≈ 1450 °C ≈ 1250 °C CO2-release from raw materials ** C3S: 1.80 g / ml C3S C4A3s: 0.56 g/ml C4A3s grindability medium easy gypsum addition ≈ 4-8 wt.-% ≈ 20-25 wt.-% w/c total hydration ≈ 0.4 ≈ 0.8 hydration products C-S-H phases, CH, AFt, … AFt, AFm, Al(OH)3 gel

** Gartner E., Cem. Concr. Res. 34 (2004), 1489. * Cement notation: C = CaO, S = SiO2, A = Al2O3, F = Fe2O3, H = H2O, s = SO3

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SLIDE 4

CSA-Cements …

… have attracted new interest during the climate debate as they: need lower burning temperatures, release less CO2 from the raw meal (less limestone), yield a higher volume of hydrate phases (higher water/ cement ratio) compared to ordinary Portland cement. Besides that, they are of interest concerning waste encapsulation. But they have some drawbacks: environment (SO2 release) risk of expansion (ettringite is main hydration product)

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SLIDE 5

CSA-cements: risk of expansion

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United States Patent 4409030, 1983: Material for destroying concrete structures … comprises a mixture of … coarse-grained quicklime … and … cement. The cement may contain calcium sulfoaluminate ... The material is blended with water and then injected into holes formed in the body to be destroyed, the material expanding as it hydrates to crack and fracture the body. Basic research is needed to understand the hydration mechanisms of calcium sulfoaluminate based systems !

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SLIDE 6

Hydration of pure ye‘elimite

(1) C4A3s + 18 H C3A·CsH12 + 2 AH3

(monosulfate)

(2) C4A3s + 2 CsH2 + 24 H C3A·3CsH32 + 2 AH3

(ettringite)

(3) C4A3s + 6 CH + 8 CsH2 + 74 H 3 C3A·3CsH32

6 consumption of calcium sulfate

reaction (2) reaction (1)

40 80 120 160 200 2 4 6 8 10 12 14 16 18 heat flow / J/(g·h) time / h

C4A3s C4A3s / CsH2 1:1 (mol) C4A3s / CsH2 1:2 (mol) C4A3s / CsH2 1:3 (mol) C4A3s / CsH2 1:4 (mol)

heat flow calorimetry w/c = 2

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SLIDE 7

5 10 15 20 25 30 35 8 16 24 32 40 48 heat flow / J/(g·h) time / h

CSA clinker CSA / gypsum 86/14 CSA / gypsum 76/24 CSA / gypsum 68/32 CSA / gypsum 61/39 OPC, w/c = 0.50

Hydration kinetics of CSA cements: influence of calcium sulfate

5 10 15 20 25 30 35 8 16 24 32 40 48 heat flow / J/(g·h) time / h

CSA clinker CSA / anhydrite 86/14 CSA / anhydrite 76/24 CSA / anhydrite 68/32 CSA / anhydrite 61/39 OPC, w/c = 0.50

dead-burnt anhydrite

w/c 0.70

gypsum *

w/c 0.70

calcium sulfate with poor reactivity: „chaotic“ early hydration reactive calcium sulfate: enables to control early hydration

* amounts of gypsum given as anhydrous calcium sulfate

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SLIDE 8

Strength development of CSA cements

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20 40 60 80 100 120 0.1 1 10 100 compressive strength / MPa time / d

CSA clinker CSA / gypsum 86/14 CSA / gypsum 68/32 OPC, w/c = 0.50 w/c = 0.70

EN 196-1 - mortars very high strength despite high water/cement-ratio gypsum increases early strength

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SLIDE 9

Used CSA-cements - composition

9

wt.-% CSA-1 CSA-2 CaO 35.4 41.2 SiO2 3.2 6.9 Al2O3 35.5 26.8 Fe2O3 0.88 0.88 MgO 0.76 0.75 Na2O 0.05 0.13 K2O 0.21 0.40 TiO2 1.8 1.2 SO3 16.8 19.5 L.O.I. 5.1 1.84

chemical analysis

wt.-% CSA-1 CSA-2 C4A3s 50 54 CA 8

  • C2AS

15

  • C2S
  • 17

Cs

  • 22

CsH2 22

  • thers *

5 7

potential phase content

* mainly titanium containing phases

water/cement ratio

CSA-1: 0.72 CSA-2: 0.80

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SLIDE 10

Isothermal heat flow calorimetry

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5 10 15 20 25 30 35 8 16 24 32 40 48 heat flow / J/(g·h) time / h

CSA-1 CSA-2

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SLIDE 11

Hydration (XRD) of CSA-1

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10 15 20 25 30 35 40 45 50 55 60 2Θ / ° 3000 6000 9000 12000 15000 18000 5 intensity / -

unhydrated 2 h 5 h 8 h 2 d 7 d G G G G Y Y Ge

Y - ye'elimite C - calcium aluminate Ge - gehlenite

C

G - gypsum

16 h M

M - monosulfate

28 d E E EE Ge G M 1 h

E - ettringite

E E

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SLIDE 12

Hydration (TGA) of CSA-1

12

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated

gypsum

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h

gypsum ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h

gypsum ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 5 h

gypsum ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 5 h 8 h

gypsum ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 5 h 8 h 16 h

ettringite Al(OH)3 - gel monosulfate

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 5 h 8 h 16 h

ettringite Al(OH)3 - gel monosulfate

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 5 h 8 h 16 h 2 d

gypsum ettringite Al(OH)3 - gel monosulfate

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 5 h 8 h 16 h 2 d 7 d

gypsum ettringite Al(OH)3 - gel monosulfate

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 5 h 8 h 16 h 2 d 7 d 28 d

gypsum ettringite Al(OH)3 - gel monosulfate

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SLIDE 13

Pore solution composition of CSA-1

0.0001 0.001 0.01 0.1 1 10 100 1 10 100 1000 concentration / mmol/l time / h Fe Si OH Na S Ca K Al

13

10.7 12.7 pH

consumption

  • f gypsum
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SLIDE 14

Hydration (XRD) of CSA-2

14

5 10 15 20 25 30 35 40 45 50 55 60 2Θ / ° 3000 6000 9000 12000 15000 18000 intensity / -

2 h 4 h 6 h 16 h 7 d unhydrated Y Y Y Y A B

Y - ye‘elimite B - belite A - anhydrite S - strätlingite (C2ASH8)

28 d E E E E S S M Y

M - monosulfate

2 d M

E - ettringite

1 h E E

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SLIDE 15

Hydration (TGA) of CSA-2

15

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h

ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h

ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 4 h

ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 4 h 6 h

ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 4 h 6 h 16 h

ettringite Al(OH)3 - gel

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 4 h 6 h 16 h 2 d

ettringite Al(OH)3 - gel monosulfate

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 4 h 6 h 16 h 2 d 7 d

ettringite Al(OH)3 - gel monosulfate

  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 700 800 900 1000

  • diff. rel. weight / %/K
  • rel. weight / %

temperature / °C

unhydrated 1 h 2 h 4 h 6 h 16 h 2 d 7 d 28 d

ettringite Al(OH)3 - gel strätlingite monosulfate

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SLIDE 16

Pore solution composition of CSA-2

0.0001 0.001 0.01 0.1 1 10 100 1 10 100 1000 concentration / mmol/l time / h Fe Si OH Na S Ca K Al

16

10.9 12.9 pH

consumption

  • f anhydrite
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SLIDE 17

Microstructure of CSA-1 and CSA-2

16 h 28 d

20 µm CSA-1, 28 d 20 µm CSA-1, 16 h

G C E Gel

CSA-1

E = ettringite C = clinker G = gypsum Gel = gel-like phases

CSA-2

20 µm CSA-2, 16 h

C Gel E

S = strätlingite

17 17

20 µm CSA-2, 28 d

S S S S

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SLIDE 18

Thermodynamic modelling

C4A3s, CA, C2S

=> Dissolution kinetics (XRD)

Composition of cement

I Slowly soluble solids K2O Na2O MgO

18

K2SO4 Na2SO4 CaO

II Rapid soluble solids

gypsum anhydrite

III Water

H2O

www.empa.ch/cemdata Lothenbach B., Winnefeld F., Cem. Concr. Res. 36 (2006), 209.

thermodynamic modelling

GEMS-PSI

ettringite C-S-H monosulfate Al(OH)3 gel

Ca2+ CaOH+ speciation CaSO4

strätlingite, …

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SLIDE 19

Modelling: solid phases of CSA-1

19

10 20 30 40 50 60 70 80 1 10 100 1000 amount / g/100 g cement time / h

pore solution C4A3s CA inert phases (C2AS, CT) gypsum ettringite monosulfate Al(OH)3 gel lines: modelling data points: XRD (C4A3s, CA) TGA (pore solution)

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SLIDE 20

Modelling: liquid phases of CSA-1

20

0.01 0.1 1 10 100 1 10 100 1000 c

  • n

c e n t r a t i

  • n

m m

  • l

/ l time / h Ca Na S OH K Al

lines: modelling data points: experimental

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SLIDE 21

Modelling: solid and liquid phase of CSA-2

Up to now, the hydration has been modelled only with insufficient accuracy (poor correlation with experimental data, especially with pore solution composition), mainly due to: some uncertain thermodynamic data (e. g. CAH10) kinetic restraints (slow dissolution of anhydrite) => work in progress

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SLIDE 22

Conclusion – hydration of CSA cements (I)

Solid phases: ettringite formation until CaSO4 is (almost) used, then monosulfate occurs Al(OH)3 gel forming by-product of hydration with C2S als minor phase (CSA-2) strätlingite forms after 28 d dissolution of calcium sulfates hindered Pore solution: first hours: dominated by alkalis, calcium and sulfate pH 10.5 - 10.8 when CaSO4 (almost) used: mainly alkalis, OH and Aluminum pH 12.5 - 12.8 after 28 d

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SLIDE 23

Conclusion – hydration of CSA cements (II)

Microstructure: CSA-1: quite dense already after 18 hours, very dense after 28 days despite high w/c of 0.72 CSA-2: dense, but inhomogeneous large strätlingite crystals after 28 days Application: binder for various applications (e. g. „plaster“boards) acceleration of OPC or slag hydration in ternary blends also incorporatng gypsum or anhydrite shrinkage reducing / expansive agent waste encapsulation

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