Numerical Simulations of Atmospheric Carbonation in Concrete Components of a Deep Geological...
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Transcript of Numerical Simulations of Atmospheric Carbonation in Concrete Components of a Deep Geological...
Numerical Simulations of Atmospheric Carbonation in Concrete Components of a Deep Geological Intermediate Low Level Waste Disposal
NUCPERF 2012
P. Thouvenot1, O. Bildstein1, S. Poyet2, I. Munier3 , B. Cochepin3 , X. Bourbon3 , E. Treille3
1 CEA (French Alternative Energies and Atomic Energy Commission), LMTE, Cadarache
2 CEA (French Alternative Energies and Atomic Energy Commission), LECBA, Saclay
3 ANDRA (French Radioactive Waste Management Agency)
FRENCH CONCEPT : RADWASTE REPOSITORY IN A CLAYSTONE FORMATION AT 500 M DEPTH
Current design of deep underground repository for high and intermediate level long-lived waste
FRENCH CONCEPT : RADWASTE REPOSITORY IN A CLAYSTONE FORMATION AT 500 M DEPTH
Atmospheric carbonation of overpack during the operating period
• Bitumized waste• Cemented waste• Compacted metallic waste• Organic waste
CARBONATION ISSUES FOR RADWASTE REPOSITORY
Ventilation (100 years)
DRYING AND CARBONATION PROCESSES IN ILLW OVERPACK
Dry air
(Rh = 40 %)
T = 25°C to 50°C
SlWater vapor diffusion
CO2 gas diffusion
T
Aqueous diffusion of reactants
Two phase water/air flow
Dissolution/precipitation : porosity reduction, permeability variations
Brine formation
CO2 gas dissolution
Dry air
(Rh = 40 %)
T = 25°C to 50°C
SlWater vapor diffusion
CO2 gas diffusion
T
Aqueous diffusion of reactants
Two phase water/air flow
Dissolution/precipitation : porosity reduction, permeability variations
Brine formation
CO2 gas dissolution
PHENOMENOLOGY: CAPILLARY FLOW
Flow law (generalized Darcy law):
Lowering of the dew point due to capillary effects
(Kelvin equation in EOS 4):
Water relative permeability (Van Genuchten):
Gas relative permeability (Corey):
Klinkenberg effect (gas flow at low pressure):
)(
gPkkF r
))(ln()( lrw
wrcap ShM
RThP
21
11)(
m
mrrrrl SSSk
lrls
lrlr SS
SSS
22 ˆ1ˆ1 SSk rg grlr
lrl
SS
SSS
1
ˆ
rgg kp
kk
1int
PHENOMENOLOGY: DIFFUSION
Air and water gases diffusion:
CO2 and other gases:
Aqueous diffusion:
Effective diffusion :
Tortuosity (Millington-Quirk):
15,273
15,273,, 000,,0,,0
T
P
PTPdTPd ii
M
RT
PNd
RTd i
8
23 2,,0
TR
Edd a
KOHi
1
15,298
1exp15,298,,,0 2
0,,0, ii dD
baS 0
PHENOMENOLOGY: DIFFUSION
Air and water gases diffusion:
CO2 and other gases:
Aqueous diffusion:
Effective diffusion :
Tortuosity (Millington-Quirk):
15,273
15,273,, 000,,0,,0
T
P
PTPdTPd ii
M
RT
PNd
RTd i
8
23 2,,0
TR
Edd a
KOHi
1
15,298
1exp15,298,,,0 2
0,,0, ii dD
baS 0
1st MAJOR COUPLING EFFECT!! Sliq
Di,g
DRYING PHENOMENON : PARAMETERS VALUES
3 different concrete materials:• High Performance Concrete (HPC)• Intermediate Performance Concrete (IPC)• Low Performance Concrete (LPC)
HPC IPC LPC
Porosity 0.08 0.12 0.16
Intrinsic permeability to liquid (m²) 1e-21 1e-19 1e-17
Intrinsic permeability to gas (m²) 1e-19 1e-17 1e-15
Relative permeability m – Slr – Sls – Sgr0.481 – 0.0 – 1.0 –
0.00.424 – 0.0 – 1.0 –
0.00.367 – 0.0 – 1.0 – 0.0
Capillarity pressure m – P0 (MPa) – Pmax (MPa) 0.481 – 45 - 1500 0.424 – 15 - 1500 0.367 – 5 - 1500
Molecular diffusion coefficient gaseous phase (m²/s) water
2.4e-05
Molecular diffusion coefficient gaseous phase (m²/s) CO2 1.6e-05
Molecular diffusion coefficient in aqueous phase (m²/s) 1.9e-09
Millington-Quirk a parameter 2
Millington-Quirk b parameter 4.2
Klinkenberg parameter (MPa) 0.45
SIMULATIONS CONFIGURATION
1D half section package container (section = 11 cm) Carbonation on both sides Ventilation air at 25°C and 40% relative humidity Initial liquid water saturation assumed to be 0.8
11 cm
25°C40%RH
25°C40%RH
DRYING RESULTS
TR EOS9 (Richards) and TR EOS4 (full multiphase) comparison
Drying process slows down when transport characteristics of concrete are enhanced.
Drying with Richards’ equation (EOS9 without gaseous diffusion) is slightly slower than with full multiphase model (EOS4).
NUMERICAL RESOURCES FOR CARBONATION SIMULATIONS
Simulations performed with Intermediate Performance Concrete
for aqueous species and mineral phases
full multiphase flow
CHEMICAL PARAMETERS
Primary phases
Secondary phases
Kinetics of dissolution / precipitation
nnnn Akr 1
15,298
11exp15,298 TR
EkTk a
n
Phase Volume %
Calcite 72.12
Portlandite 5.73
CSH 1.6 13.76
Monocarboaluminate 2.26
Ettringite 3.60
Hydrotalcite 0.39
Hydrogarnet-Fe (C3FH6) 2.05
Phase type Phases
Oxides Magnetite, Amorphous silica
Hydroxides Brucite, Gibbsite, Fe(OH)3
Sheet silicates Sepiolite
Other silicates CSH 1.2, CSH 0.8, Straetlingite, Katoite_Si
Sulfates, chlorides, other salts Gypsum, Anhydrite, Burkeite, Syngenite, Glaserite, Arcanite, Glauberite, Polyhalite
Carbonates Calcite, Nahcolite
Other Hydrotalcite-CO3, Ettringite, Dawsonite
CHEMICAL PARAMETERS
Primary phases
Secondary phases
Kinetics of dissolution / precipitation
nnnn Akr 1
15,298
11exp15,298 TR
EkTk a
n
Phase Volume %
Calcite 72.12
Portlandite 5.73
CSH 1.6 13.76
Monocarboaluminate 2.26
Ettringite 3.60
Hydrotalcite 0.39
Hydrogarnet-Fe (C3FH6) 2.05
Phase type Phases
Oxides Magnetite, Amorphous silica
Hydroxides Brucite, Gibbsite, Fe(OH)3
Sheet silicates Sepiolite
Other silicates CSH 1.2, CSH 0.8, Straetlingite, Katoite_Si
Sulfates, chlorides, other salts Gypsum, Anhydrite, Burkeite, Syngenite, Glaserite, Arcanite, Glauberite, Polyhalite
Carbonates Calcite, Nahcolite
Other Hydrotalcite-CO3, Ettringite, Dawsonite
amorphous CSH phases
CARBONATION RESULTS
pH decrease, portlandite dissolution and calcite precipitation over a thickness of about 2 cm after 100 years
CARBONATION RESULTS
Dissolution of CSH 1.6, ettringite, monocarboaluminate and hydrotalcite on 2 cm after 100 years
Precipitation of CSH 1.2, CSH 0.8, straetlingite, amorphous silica and gypsum on the same thickness
Precipitation of small amounts of sepiolite, gibbsite and katoïte-Si is also predicted
CARBONATION RESULTS
from a performance assessment point of view:
looking at the different concrete performance
similar paragenesis from 1 cm to 4 cm after 100 years
sensitivity calculations on diffusion properties a and b (tortuosity parameters)
less than 1 cm (a, b +50% with HPC) in 100 years complete carbonation - 5.5 cm - (a, b -50% with LPC) in
25 years
CARBONATION RESULTS: COMPARISON WITH EXPERIMENTAL RESULTS
Modeling results- alteration is complete (amorphous silica)- no residual primary phases (portlandite)
CARBONATION RESULTS: COMPARISON WITH EXPERIMENTAL RESULTS
Modeling results- alteration is complete (amorphous silica)- no residual primary phases (portlandite)
Experimental results- residual primary phases (portlandite) alteration is not complete
Distance (mm)
Calcite front
Portlandite front
Drouet, 2010
CARBONATION RESULTS
Effect of water content on reactivity (Bazant type function)
2nd MAJOR COUPLING EFFECT!!
Sliq
diffusionchemical reactivity
CARBONATION RESULTS
Effect of water content on reactivity (Bazant type function)
2nd MAJOR COUPLING EFFECT!!
Sliq
diffusionchemical reactivity
CARBONATION RESULTS
Significant reduction in the amplitude of carbonation (less dissolution of portlandite and CSH 1.6 and less precipitation of amorphous silica and other secondary CSH)
Lower reactivity accompanied by a greater penetration of carbonation front due to lower consumption of CO2 at the surface
Effect of water content on reactivity (Bazant type function)
CARBONATION RESULTS
Significant reduction in the amplitude of carbonation (less dissolution of portlandite and CSH 1.6 and less precipitation of amorphous silica and other secondary CSH)
Lower reactivity accompanied by a greater penetration of carbonation front due to lower consumption of CO2 at the surface
Effect of water content on reactivity (Bazant type function)
CARBONATION RESULTS
Significant reduction in the amplitude of carbonation (less dissolution of portlandite and CSH 1.6 and less precipitation of amorphous silica and other secondary CSH)
Lower reactivity accompanied by a greater penetration of carbonation front due to lower consumption of CO2 at the surface
Effect of water content on reactivity (Bazant type function)
CONCLUSIONS Drying process of 11 cm thick waste packages depends strongly on
the concrete nature and slightly on the flow model (Richards or full multiphase)
Considering full multiphase model, carbonated depth is about 2 cm after 100 years for the Intermediate Performance Concrete. degraded thickness is totally carbonated (total dissolution of primary mineral phases)
If we consider a chemical reactivity depending on the liquid saturation (Bazant type function), a considerable reduction in the amplitude of carbonation and a greater penetration of carbonation front are observed
calibration with accelerated carbonation experiments (Drouet, 2010)
also: need for improved knowledge on kinetics parameters and thermodynamic data, especially for CSH with low Ca/Si ratio
Other perspectives include:
• taking into account a protective effect of secondary minerals
• modeling corrosion of rebars