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2 nd Mechanisms and modelling of waste/cement interactions, Le Croisic, October 13, 2008. Hydration of calcium sulfoaluminate cement by a zinc chloride solution Application to nuclear waste conditioning S.Berger 1 , C. Cau dit Coumes 1 , D.

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SLIDE 1

2nd Mechanisms and modelling of waste/cement interactions, Le Croisic, October 13, 2008.

Hydration of calcium sulfoaluminate cement by a zinc chloride solution

Application to nuclear waste conditioning

S.Berger1, C. Cau dit Coumes1, D. Damidot2, P.Le Bescop3

  • 1. Atomic Energy Commission, Marcoule Research Center, France.
  • 2. Civil & Environmental Egineering Departement – Ecole des Mines de Douai, France.
  • 3. Atomic Energy Commission, Saclay Research Center, France.
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SLIDE 2

Context

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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Zinc chloride is a soluble salt contained in ashes resulting from the incineration of α radioactive wastes including neoprene and polyvinylchloride. Deleterious effects on Portland cement:

  • setting is strongly delayed and can be inhibited at high zinc chloride

loading (Arliguie 1985),

  • hydration and hardening are slowed down (Ortego 1989).

5 10 15 20 25 30 35 20 40 60 80 100 120 140

Time (h) Temperature rise (°C)

From Cau-dit-Coumes and al, ICCC 2007

> 4 days

Portland Cement with 0,1 mol/L ZnCl2 Portland Cement without ZnCl2

< 24 h

Precipitation of β2-Zn(OH)2 or Zn2Ca(OH)6.2H2O over the cement grains has been postulated to explain the delay in cement hydration (Arliguie 1985). It is necessary to select a binder having a different chemistry, more compatible with the waste:

a calcium sulfoaluminate cement.

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SLIDE 3

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

3

Objective: to investigate the influence of zinc chloride on

the hydration of CSA cements.

I. Materials and Methods II. Kinetics of hydration III. Mineralogical evolution IV. Conclusion and prospects

Overview

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SLIDE 4

Materials:

cement composition and hydration

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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Mineralogical composition of the CSA clinker (KTS 100 provided by Bellitex):

Minerals (% weight) C4A3S C2S C3FT C12A7 Periclase CS Quartz 71 16 6.6 3.1 2.6 0.5 0.5

Two main features of CSA cement hydration: Major heat output

20 30 40 50 60 70 80 10 20 30 40 Time (h) Temperature (°C)

Portland cement CSA cement

semi-adiabatic Langavant calorimetry

Influence of temperature and gypsum content has to be studied. Hydrates proportion depend of the amount

  • f gypsum mixed with the clinker.

10 20 30 40 50 60 70 80 90 100 4 , 9 9 , 4 1 3 , 4 1 7 , 1 2 , 5 2 3 , 7 2 6 , 6 2 9 , 2 3 1 , 7 3 4 , 1 3 6 , 2 3 8 , 3 4 , 2

% gypsum % hydrates

Modified from Glasser and al, CCR 2001

AH3 Ettringite Calcium monosulfo aluminate hydrate CSH Gypsum

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SLIDE 5

Materials and methods:

preparation of specimens

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

5

  • CSA cements preparation: mixing of ground CSA

clinker with gypsum (0-10%, 20% and 35%).

  • Mixing solution: dissolution of ZnCl2 salt (0 or 0.5

mol/l) into distilled water.

  • Water to cement ratio: 0.55 for pastes and mortars.
  • Sand to cement ratio : 3, sand and cement pre-mixed.

Two kinds of specimens were prepared:

  • pastes for XRD analysis,

(hydration stops at 5min, 1h, 2h, 5h, 24h, 7days,…)

  • mortars for semi-adiabatic

Langavant calorimetry. After mixing, samples were cured 7 days in sealed plastic bag at 20°C or were submitted to a thermal cycle in an oven.

20 40 60 80 50 100 150 Time (h) Temperature (°C)

Temperature evolution recorded on CSA mortars

semi-adiabatic Langavant calorimetry

Thermal cycles: temperature profiles made from the temperature evolution of mortars under semi-adiabatic conditions and applied on pastes to reproduce the temperature rise and decrease which may occur in a massive structure during cement hydration.

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SLIDE 6

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

6 20 40 60 80 1 2 3 4 5 Time (h) Temperature (°C)

Materials and methods:

preparation of specimens

Differences between the thermal evolution of two mortar samples cured at 20°C or under semi- adiabatic conditions were very significant.

20 40 60 80 2 4 6 8 10 12 14 16 18 20 Time (h) Temperature (°C)

20°C curing semi-adiabatic curing paste 20% gypsum 0.5 mol/l ZnCl2 mortars, 10% gypsum inner temperature calorimetry recorded on mortar temperature profile applied to the paste Temperature profiles were defined by interpolating in 20-40 segments the curves recorded on mortars. Some corrections were required to keep the inner temperature of the paste near that of the mortar under semi-adiabatic curing.

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SLIDE 7

Kinetics of hydration:

influence of gypsum content

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

7

50 100 150 200 250 300 350 400 450 500 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (h) Cumulated heat (J/g of cement)

0% 2% 1% 3% 5% 7% 10%

Two effects were observed when the gypsum content increased from 0 to 10%:

  • the cumulated heat output was reduced when the gypsum content exceeded 5%,
  • the induction period decreased strongly especially at low gypsum contents.
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SLIDE 8

Kinetics of hydration:

influence of gypsum content

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

8

50 100 150 200 250 300 350 400 450 500 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (h) Cumulated heat (J/g of cement)

0% 10% 20% 35%

Beyond a gypsum content of 10%, heat output and induction period did not vary anymore.

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SLIDE 9

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 5 10 15 20 25

Time (h)

Reacted yeelimite / 5 min (%) 0% gypsum 10% gypsum 20% gypsum 35% gypsum

Kinetics of hydration:

influence of gypsum content

Without gypsum:

  • yeelimite started to react much later,

in agreement with the long induction period previously observed.

  • Yeelimite was almost totally depleted

at 24h while with gypsum, 10 to 20% were still unreacted. Mineralogical study on pastes with thermal cycles : Gypsum reactivity:

  • gypsum dissolution before that of yeelimite,
  • almost total depletion at 5h.

0% 20% 40% 60% 80% 100% 5min 1h 2h 5h Time Reacted gypsum and yeelimite /5min (%) gypsum, 10, 20 and 35% gypsum yeelimite, 10, 20 and 35% gypsum

(based on XRD relative peak areas) (based on XRD relative peak areas)

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SLIDE 10

Kinetics of hydration:

influence of thermal cycle

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

10 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0% 10% 20% 35% Gypsum content (%) Reacted yeelimite at 1 day /5min (%)

cycle 1 day no cycle 1 day no cycle 7 days

(based on XRD relative peak areas)

The thermal cycle promoted the dissolution of yeelimite: amount of yeelimite consumed at 1 day higher than that depleted at 7 days when curing is performed at 20°C.

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SLIDE 11

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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Kinetics of hydration:

influence of zinc chloride addition

50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time (h) Cumulated heat (J/g of cement)

0.5 mol/l

With gypsum Without gypsum

0 mol/l 0 mol/l 0.5 mol/l

  • A retardation was observed, but its magnitude was much smaller than

that recorded with OPC.

  • Setting inhibition was never observed: setting occurred in less than 2h

with gypsum, and in less than 24h without it.

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SLIDE 12

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time (h) Cumulated heat (J/g of cement) 50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time (h) Cumulated heat (J/g of cement) 50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time (h) Cumulated heat (J/g of cement)

Kinetics of hydration:

influence of zinc chloride addition

CaCl2 ZnCl2 Zn(NO3)2 Ca(NO3)2 CaSO4 ZnSO4 Salt concentration : 0.5 mol/l

acceleration Zn2+ > Ca2+ delay Investigating the reactivity of zinc cations and chloride anions

0% gypsum H2O Temperature of the mixing solution: 20°C

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SLIDE 13

Kinetics of hydration:

influence of zinc chloride addition

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

13

Investigating the reactivity of zinc cations and chloride anions

50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time (h) Cumulated heat (J/g of cement) 50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time (h) Cumulated heat (J/g of cement)

CaCl2 ZnNO3)2 CaSO4 ZnSO4 Ca(NO3)2 ZnCl2

Temperature of the mixing solution: 20°C

acceleration SO4

2- >> 2 NO3

  • > 2 Cl-

delay

Salt concentration : 0.5 mol/l Chloride anions strongly slowed down hydration but zinc cations accelerated it.

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SLIDE 14

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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0% 20% 40% 60% 80% 100% 10 20 30 40

Gypsum (%)

Area/area with 35% gypsum (%)

Ettringite relative peak area

Lin (Counts)

1000 2000 3000 4000 5000 6000 7000 8000 9000

2-Theta - Scale

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Mineralogical evolution:

influence of gypsum 24h XRD

0% gypsum 10% gypsum 20% gypsum 35% gypsum E E M G M G E E Y M E

E: C3A.3CS.H32 M: C3A.CS.H12 G: CSH2 Y: C4A3S A: AH3

A A G E Gypsum promoted ettringite precipitation.

(based on XRD relative peak areas)

with thermal cycle

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SLIDE 15

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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2-Theta - Scale

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

2-Theta - Scale

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2

0% gypsum 0% gypsum, thermal cycle 10% gypsum 10% gypsum, thermal cycle

E E E M M E E A A E E M + E CAH10 CAH10 E E M A A

Mineralogical evolution:

influence of thermal cycle and gypsum content 24h XRD E: C3A.3CS.H32 M: C3A.CS.H12 Y: C4A3S A: AH3

Thermal cycle promoted precipitation of calcium monosulfoaluminate hydrate instead of ettringite. This effect was enhanced in absence of gypsum. CAH10 was unstable with gypsum and/or temperature rise.

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S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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2-Theta - Scale

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

E E E E E G M + E E G E E

2-Theta - Scale

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

E E E E E E E G G E E

20% gypsum 20% gypsum, thermal cycle 35% gypsum 35% gypsum, thermal cycle

Mineralogical evolution:

influence of thermal cycle and gypsum content 24h XRD E: C3A.3CS.H32 M: C3A.CS.H12 G: CSH2 Y: C4A3S A: AH3

With 20% and more of gypsum, the thermal cycle had no significant effect on the mineralogy: gypsum stabilized ettringite in spite of the temperature increase. Gypsum influence seemed to prevail over temperature effect.

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SLIDE 17

Mineralogical evolution:

influence of zinc chloride addition 7 days XRD

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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Lin (Counts)

200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 5 10 20 30

Chloride-containing minerals were identified:

0% gypsum 0% gypsum, 0.5 mol/l

  • Kuzel’s salt, K: 3CaO-Al2O3-0.5CaCl2-0.5CaSO4-12H2O
  • Friedel’s salt, F: 3CaO-Al2O3-CaCl2-10H2O

E C A H

1

E CAH10 E E Y Y Y E E + M E: C3A.3CS.H32 M: C3A.CS.H12 G: CSH2 Y: C4A3S A: AH3 H: Hemicarbonate

2-Theta - Scale

H K K K K + F + H Y Y E E F F No detection of any zinc containing crystallized phase by XRD.

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SLIDE 18

Mineralogy evolution:

influence of zinc chloride addition

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

18

2-Theta - Scale

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 2

2-Theta - S cale

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 2

E CAH10 M CAH10 E E Y Y E

7 days XRD Influence

  • f thermal cycle

Influence

  • f gypsum (20%)

K F E A M M F K A 0% gypsum, 0.5 mol/l 0% gypsum, 0.5 mol/l, thermal cycle 0% gypsum, 0.5 mol/l 20% gypsum, 0.5 mol/l CAH10 E E Y E E E E E Y E K K F E + M K: 3CaO-Al2O3-0.5CaCl2-0.5CaSO4-12H2O ; F: 3CaO-Al2O3-CaCl2-10H2O

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SLIDE 19

Mineralogical evolution:

influence of zinc chloride addition

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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With thermal cycle and 20% gypsum

2 -T h e ta - S ca le

6 7 8 9 1 0 1 1 1 2 1 3 1 4 15 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3

E C A H

1

E E E + M E K F E F Y G E E E GK

7 days XRD

K: 3CaO-Al2O3-0.5CaCl2-0.5CaSO4-12H2O F: 3CaO-Al2O3-CaCl2-10H2O 0% gypsum, 0.5 mol/l 20% gypsum, 0.5 mol/l, thermal cycle Gypsum promoted ettringite precipitation instead of all AFm phases. However, Friedel’s salt seemed to be stabilized by a temperature rise and a strong chloride concentration.

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SLIDE 20

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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Conclusion

CSA cements showed a much better compatibility with zinc chloride than OPC: hydration was slightly slowed down but setting inhibition was never

  • bserved.

Chloride anions induced a strong retardation, but this effect was balanced by zinc cations and sulfate anions from gypsum. In the presence of zinc chloride, the mineralogy observations revealed the precipitation of chloro-AFm such as Kuzel’s salt and Friedel’s salt. The thermal history of the samples proved to be a key parameter since a temperature rise accelerated the rate of hydration and modified the nature

  • f the hydrates, particularly with a low gypsum content.
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SLIDE 21

S.Berger, Cau dit Coumes and al ; Hydration of calcium sulfoaluminate cement by a zinc chloride solution

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Prospects

  • to find the location of zinc cations,
  • to identify the mechanisms which inhibit or accelerate the hydration,
  • to investigate the influence of zinc chloride and temperature on the

properties of the hardened materials (porosity, compressive strength, length change, durability,…).