NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE
COMPONENTS IN A DEEP GEOLOGICAL RADWASTE DISPOSAL SITE DURING
OPERATING PERIOD
L. Trotignon1, P. Thouvenot1, I. Munier2, B. Cochepin2, E. Piault1, E. Treille2, X. Bourbon2
and S. Mimid1
1 CEA, Direction de l’Energie Nucléaire, DTN/SMTM/LMTE, CE Cadarache, France
2 Andra, Scientific Division, Châtenay-Malabry, France
Corresponding author :
Dr. Laurent TROTIGNON
CEA, Direction de l’Energie Nucléaire
DTN/STRI/LMA
Bât.708
CE Cadarache
13108 Saint Paul lez Durance
France
Phone : 33 4 42 25 26 78
Fax : 33 4 42 25 77 88
e-mail: laurent.trotignon@cea.fr
Total number of pages (including title page): 48
Total number of tables: 6
Total number of figures: 16
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
ABSTRACT
Simulations of atmospheric carbonation of concrete intermediate-low level waste (ILLW) cell
components were conducted to evaluate potential chemical degradations affecting these
components during the operating period of a radioactive waste repository, in a deep CallovoOxfordian clay layer. Two-phase liquid water-air flow is combined with gas components
diffusion processes, leading to a progressive drying of the concrete and an array of chemical
reactions affecting the cement paste. The carbonation process depends strongly on the
progression of the drying front inside the concrete, which in turn is sensitive to the initial
water saturation and to nonlinear effects associated with permeability and tortuosity
phenomenological laws.
Results obtained with a modified version of ToughReact-EOS4, in order to represent realistic
tortuosity evolution of materials with clogging and saturation are presented and commented
upon. Strong porosity clogging of the carbonated concrete is not observed in the simulations;
slight porosity opening is in general predicted, except for high initial liquid saturation of the
concrete, in which case a moderate porosity reduction is found. Carbonation depths in the
order of 0.6 to 1.0 10-3 m y-1 are predicted for cementitious components. However, these
values are probably overestimations both in depth and intensity of carbonation. The model of
cement drying needs some revision in order to correctly weight diffusion control in the
discretized representation of the cement/air boundary. Also the kinetic model of mineral
reactivity needs improvements with respect to the influence of liquid saturation on reaction
rates, which are actually strongly decreased in dry materials, and with respect to the protective
effect of secondary carbonates.
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
I. INTRODUCTION
Andra1 has elaborated concepts to establish the feasibility of a high-level waste (HLW) and
intermediate-level long-lived radioactive waste (ILLW) disposal in the deep CallovoOxfordian clay-stone geological formation at the Meuse/Haute-Marne site in the eastern part
of the Paris Basin. During the operating period within an ILLW disposal zone (up to 100 y), a
number of the concrete components (waste package containers, lining, and disposal cell
backfill—Fig. 1) will be subjected to ventilation in order to guarantee operating safety and
contribute to evacuation of residual heat from low-heat-emitting ILLW (temperatures below
~40°C are expected). Ventilation air will be drawn from the surface and will exchange water
and heat with the clay host rock leading to “dry” air conditions (relative humidity lower than
50%). This will generate a desaturation of concrete components, participating to atmospheric
carbonation development and potentially leading to a progressive lowering of pH inside the
cement paste. This could trigger corrosion of the steel reinforcement, which may have
deleterious effects on the concrete.
Simplified approaches have been developed to model atmospheric carbonation processes
(Bary et al.2,3; Thiery et al.4). However, a more complete and detailed modelling of this
process is required, which can only be achieved with reactive-transport numeric tools.
Preliminary simulations of carbonation processes were obtained in 1D geometry with a
modified version of the reactive transport code TOUGHREACT5, taking into account
extended tortuosity models of cement pastes. These simulations consider a complex
mineralogical composition of cementitious and neoformed phases, as well as porosity /
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
permeability evolutions due to precipitation/dissolution phenomena together with temperature
effects.
II. CONCEPTUALIZATION OF CONCRETE COMPONENTS
ILLW cell components constitute a complex 3D system (Fig. 1 and 2). The carbonation
process is represented in this study in simplified axial 1D geometry. Such simplification
ignores variations in hydraulic head and flow that will occur along the circumference of the
cell. Also the regions where corners or gradients in mechanical loading are found will
probably require in the future 2-D or 3-D simulations.
Two simple configurations were explored in the present work:
i)
an 1D aerated thin concrete structure (section = 0.11 m) represented on one half
using a regular cartesian mesh of 11 cells of 5 mm. It is assumed that atmospheric
carbonation occurs on both faces of the section. Boundary conditions are
represented by a single-phase gas medium (air) of infinite volume, relative
humidity of 40%, isothermal temperature (25°C, 40°C) and pressure (0.1 MPa).
Initial liquid water saturation of the material is assumed to be 0.6.
ii)
an 1.5 m thick concrete component in contact with clay-stone in a 1D radial
geometry. The radial profile extends from r = 3.5 m to r=40 m is simulated (0
being the centre of the cell). The concrete component (1.5 m thick) is in contact
with the excavation-disturbed zone (EDZ) in the clay-stone, represented by a
fractured zone (0.6 m thick) surrounded by a microfissured zone (4.5 m thick) and
then an undisturbed clay-stone zone (~30 m thick). The mesh is progressive, from
a 5 mm cell size at the air-concrete boundary to a 1 m cell size at the other end of
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
the system. The mesh includes 211 cells. At r = 3.5 m, boundary conditions are
similar to that specified for the thin structure case above. At r = 40 m, constant
pressure (4.5 MPa), temperature (25°C), and liquid saturation (0.98) are imposed.
In the concrete, an initial pressure and liquid water saturation of respectively 0.1
MPa and 0.7 are assumed. In the different clay-stone zones, the initial pressure and
liquid saturation are assumed to be respectively 4.5 MPa and 0.98.
III. SIMULATED PROCESSES AND MATERIALS PROPERTIES
III.A Processes
Atmospheric carbonation of concrete in unsaturated conditions is a complex process that
involves intricate couplings between transport of both liquid and vapour water and CO2 in gas
and liquid phases, capillary flow during drying of the concrete and chemical reactions
involving cement hydrates with CO2 dissolved in the liquid water phase (Fig. 3). Porosity
modification is also associated with carbonation. CO2 diffuses from the single-phase gas
boundary condition into the partially saturated pore space of concrete and dissolves in the
pore water. Hydrates of the cement (mainly portlandite and CSH phases) are then subject to
carbonation reactions, producing calcite and secondary minerals. A pH front progressively
develops inside the concrete, from pH ~8.5 in regions where carbonation is complete, to pH
~13.3 in the unperturbed concrete. The evaporation of pore water also leads to the formation
of Na-K-SO4-OH brines, in which specific sulphate salts are likely to precipitate.
Major processes considered in this work are:
1. Darcy flow of liquid water and air, taking into account capillary forces and the
Knudsen effect for gases.
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
The mass flux Fi of phase i is proportional to the pressure gradient in this phase (Pruess et
al.8):
Fi  k

k ri  i 

Pi   i g
i

(1)
where k is the intrinsic permeability of the porous medium (m2), kri is the relative permeability
of the medium to phase i, i is the viscosity of phase i (Pa.s), Pi is the pressure in phase i (Pa),
i is the specific mass of phase i (kg.m-3), g is gravity (m.s-2). Pi is the sum of the pressure in a
reference phase and of the capillary pressure. Vapour pressure lowering, due to capillarity
effects, are described by Kelvin’s model (Bary and Sellier3, Pruess et al.8):
pcap hr     l
RT
ln hr Sl 
Mw
(2)
where Sl is the liquid saturation of the porous medium, hr is the relative humidity at saturation
Sl , R is the gas constant (8.314 J.mol-1.K-1), T is temperature (K), Mw (kg) is the molar mass
of water , l is the specific mass of water, pcap is the capillary pressure.
Wetting properties and relative permeability of the media are expressed using the van
Genuchten-Mualem9 (liquid phase) and Corey (gaseous phase) models described in Pruess et
al8.
1 m
 

k rl Se   Se 1  1  Sem  
 
 

krl is the liquid relative permeability with S e 
Sl  Slr 
Sls  Slr 
2
(3)
being the effective saturation, Sl the
liquid saturation, Slr the residual irreducible liquid saturation and Sls the maximum liquid
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
saturation of the medium. The material parameter m is usually given as a function of n (see
1
n
Table I) as m  1 . The relative permeability for the gas phase is given by
 
2
krg  1  Sˆ 1  Sˆ 2
where Sˆ 
Sl  Slr 
1  S
lr
 S gr 

(4)
, Sl and Slr as defined above and Sgr is the residual irreducible gas
saturation. The capillary pressure is given by:

pcap ( Se )   Pr  S

where Se is the effective saturation, m  1
1

m
e

 1

1
n
(5)
1
and Pr, a characteristic pressure (Pa), are
n
material parameters (Table I).
2. Diffusion of gaseous and aqueous species
The diffusive flux of component j in phase i is expressed by
f i j   0 i  i d i j X i j
(6)
where  is the porosity, i is the specific mass of phase i, Xij is the mass fraction of
component j in phase i, dij is the diffusion coefficient of component i in phase j and 0i is an
non-dimensional quantity representing the tortuosity of phase i in the porous medium.
Both aqueous and gaseous diffusion are taken into account but focus will be here given on
gaseous diffusion which plays a major role in the processes of drying and carbonation.
Dripping is not considered in the present model and exportation of water out of the concrete is
caused by water vapour diffusion from the external boundary of the component towards dry
ventilation air. Thus, the nonlinear expression of tortuosity in the water vapour diffusion
process (Thiery et al.4; Baroghel-Bouny et al.6) plays a key role in the initiation of
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
atmospheric carbonation. For low-permeability concrete materials, expressions adopted for
the diffusion coefficient are similar to the classical Millington and Quirk7 model developed
for soils:


Di j   0 i di j    a Sib d 0j,i
(7)
where Di,j is the effective diffusion coefficient of component j in phase i, d0,i,j is the diffusion
coefficient of component i in pure phase j,  is the porosity, Si is the relative saturation with
respect to phase i. Exponent b (usually from 3 to 5) plays an important role in the dynamics of
drying, because water vapour diffusion strongly increases only when some gas-saturation
threshold is reached. Because of the corresponding nonlinear decrease with saturation of the
liquid-water relative permeability, a dry-fringe formation starts at the component boundary as
soon as capillary flow is unable to locally compensate for vapour diffusion.
The temperature dependence of the gaseous diffusion coefficient is given by (Lasaga10)
d 0,i , j 
RT
3 2PNd 2
8RT
M
(8)
3. Dissolution/precipitation of minerals
Chemical disequilibrium induced by CO2 dissolution in the interstitial water of the concrete
triggers processes of mineral dissolution and precipitation (e.g. dissolution of portlandite
followed by calcite precipitation). The rate of such processes is described in our simulations
by a law of the form
rn   k n An 1  n

(9)
where rn (mol.s-1) is the dissolution (+ sign) or precipitation (- sign) of mineral phase n, kn the
rate constant (mol.m-2.s-1), An the specific surface area (m2.mol-1), n is the saturation index of
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
mineral n,  and  are constant parameters (fixed to 1 in our simulations). The rate constant
depends on temperature through an Arrhenius law.
 E0
k n T   k 0 298,15K  exp  a
 R
1 
1
 

 T 298,15 
(10)
where k0 is the rate at 298,15 K, Ea0 the activation energy (J.mol-1), R the gas constant (8.314
J mol-1 K-1). Dissolution and precipitation are here described with symmetric rate laws;
however, if an initially absent secondary phase appears, it is necessary to specify a nucleation
surface area that will make possible initial growth. It is also possible to specify an
oversaturation threshold to be reached before precipitation starts. This feature was used in
particular for secondary zeolites. The kinetic model does not include the effect of liquid
saturation on reaction rate (through modification of reactive surface area).
4. Feedback of porosity variations on permeability and capillary properties
A Carman-Kozeny type relationship is used to update permeability as a function of porosity
changes:
1  i 2   
k  ki
1   2  i 
3
(11)
where k (resp. ki) is the updated permeability (resp. the initial permeability) and  the
porosity. Capillary pressure changes are also impacted by textural modifications of the porous
medium. The update of capillary pressure is done by using the Leverett scaling law (Xu et
al.5):
Pc  Pc ,i
ki
ki
(12)
where Pc is the updated capillary pressure as a function of initial and updated permeability
and porosity and initial capillary pressure.
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
.
5. Heat transfer
In situations where a thermal gradient exists, heat transfer by conduction and convection is
included in the simulated processes. Due to the very low permeability of concrete and claystone, heat transfer is dominated by conduction. Fractured EDZ and microfissured clay-stone
have been given the same heat capacity and thermal conductivity as unperturbed clay-stone.
Table I summarizes these parameters used for concrete and clay-stone in the simulations.
III.B Composition and physical properties of components
Components involved in the simulations are a high-performance concrete (BHP CEM-I, based
on pure Portland cement) and clay-stone (Andra1).
Physical properties
Tables 1 and 2 summarize the main hydraulic and transport properties of the considered
components. In these tables, materials are assigned an intrinsic permeability to gas larger than
the intrinsic permeability to liquid. This feature is consistent with results reported in
Baroghel-Bouny et al.6 and Thiery et al.4, who studied the drying of cement pastes. For claystone, a factor of 102 between gas and liquid intrinsic permeabilities was assumed.
Microfissured clay-stone has hydraulic properties intermediate between those of clay-stone
and fractured EDZ. The thermal properties of microfissured clay-stone and fractured EDZ are
fixed to the same value as for unperturbed clay-stone.
Composition of concrete
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
Concrete is composed of a mixture of aggregate (mainly calcite with some quartz) and cement
paste. The model composition of the concrete (Table 3) was derived from data provided by
Andra1 and Belarbi et al.11. Note that upon heating above 40°C, the equilibrium composition
of the cement paste is predicted to evolve, because of the higher stability of katoite_Si
compared to monocarbo-aluminate. The kinetics of this transition is considered to be fast.
Composition of clay-stone
A reference composition model of clay-stone was derived from data published by Andra1 and
Gaucher et al.12,13. This model is consistent with the pore-water chemistry of the clay-stone
(Table 4). The siderite considered here is an ideal mixture of 0.15 pure calcite and 0.85 pure
siderite end-members.
Secondary phases
Chemical reactions occurring at the air/concrete and clay-stone/concrete boundaries induce
the precipitation of secondary minerals. The set of secondary phases considered in our
simulations is summarized in Table 5. Secondary calcite was distinguished from aggregate
calcite, the latter being considered as an inert phase.
Kinetics of dissolution/precipitation reactions
Reactions occurring in the air/concrete/clay-stone system cover several orders of magnitude in
kinetics, from very fast reactions, like gypsum dissolution, to very slow reactions, like quartz
or illite dissolution. Because of the greater numerical stability of TOUGHREACT in the
kinetic mode, it was decided to describe all solid/solution reactions in the pure kinetic mode
and avoid the mixed kinetic/equilibrium model. However, the reaction-rate constants for
many phases, as well as the reactive surface areas, are not well known. A simplified approach
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
was therefore adopted here, combining the best data from Palandri and Kharaka14 with
information available at Andra on cementitious phases (Table VI).
IV. SIMULATION TOOLS
IV.A. Thermodynamic database
The simulations were run using the Thermoddem lv12 (July 2008) database, developed by
BRGM (Orléans, France) and available at http://thermoddem.brgm.fr/.
IV.B. Adaptation of TOUGHREACT-EOS4
The equation of state EOS4 module (Pruess et al.8) was used in this study to describe the
drying of materials like concrete, in which pressure-lowering effects are noticeable. In
addition, the choice of this EOS makes possible the correct treatment of two-phase flow
together with reactive transport in such materials. Considering Richard’s equation as an
approximation for two phase flow (EOS9 option in TOUGHREACT), and thus neglecting
diffusion control on drying, was not possible as the concrete/air boundary condition would
have, in TOUGHREACT, handled incorrectly solutes and exported them out of the concrete
with water mobilized by suction. However, several adaptations of the original EOS4 module
available in TOUGHREACT Version 1.2 (YMP Q V3.1.1 July 2006) (Xu et al.5) were
necessary:
i)
An extended model for porosity/saturation-dependent tortuosities was developed to
allow material-generalized Millington-Quirk tortuosity laws as shown in Eq. (7),
ii)
An additional factor was taken into account to fix a distinct intrinsic material
permeability with respect to the gas phase (see Physical properties in § III.B and Tables 1 and
2), consistently with material data available at Andra1 and other works (Thiery et al.4).
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
IV.C. Time and space discretization
The two-phase reactive transport process simulated here combines two major features:
i)
Development of a drying front from the edge of the porous concrete component
ii)
Transport in the gas phase of a strongly soluble reactive species, CO2(g)
It was found that the dynamics of drying are dependent on the size of the first discretization
cell of concrete in contact with the dry air boundary condition (Fig. 4). A large cell size delays
drying, owing to the control of the drying by water vapour diffusion. Among parameters
influencing the kinetics of drying, note the nonlinear effects of the initial liquid water
saturation of concrete (Fig. 5) and of the b exponent in Eq. (7) (Fig. 6).
In the TOUGHREACT version used here, gas-phase transport is not iteratively coupled to
reaction processes. It was therefore necessary to use a sequential non-iterative approach
(SNIA) for reactive transport, which requires small time steps, since gaseous CO2 transport is
a fast process (Fig. 7). A compromise was found in order to correctly describe the drying
process, obtain sufficient details about reaction fronts, and use the largest time-steps (keeping
coupling errors small). The compromise found here was to take the smallest grid cells of
5 mm size; the time-step to be used then ranges from 10 to 50 s.
The runs were performed on a Linux workstation based on IntelXeon X5365 3 GHz
processors. Duration of runs ranged from 30 to 180 days CPU to simulate up to 100 years of
physical time.
V. RESULTS
V.A. CASES
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
Several conditions were explored to represent actual disposal conditions in a simplified way,
given that the heat source, the relative humidity of air, or cell ventilation may vary during the
repository operating period. Two cases are presented in this paper:
-
thin BHP CEM-I structure test-case at 25°C, for two initial water saturations (0.6 and
0.8)
-
thick BHP CEM-I structure /clay-stone system, for two temperature scenarios: (i)
constant temperature (25°C) and (ii) initially at 25°C and submitted to hot (40°C) dry air at
the concrete boundary.
V.B. THIN STRUCTURE TEST-CASES
With the assumption of an initial saturation of 0.6, complete drying of the thin structure
proceeds in about 10 years (Fig. 8). After 50 years, the pH is depressed over a thickness of ~4
cm (1.5 cm at 10 y). The overshoot in pH, above the initial value of 13.25, results from a
hydroxyl ions overconcentration caused by drying. Ionic strength reaches values of about 2.5
molal in the dried zones. In this range of ionic strength, the HKF model implemented in
TOUGHREACT (Xu et al.5) gives fair estimations of activity coefficients for dissolved ions.
Profiles for portlandite and secondary calcite (Figure 9) show a retreat of portlandite on a
thickness of ~4.5 cm in 50 years Porosity variations, due to dissolution / precipitation of
mineral phases, (Fig. 9) are moderate: the slight pore space closure ( ~ -5 % variation in
porosity) is followed by a +5 % porosity increase in the fully carbonated zone.
Profiles for CSH phases (Fig. 10) show a degradation of CSH 1.6 towards secondary phases
(CSH 0.8, CSH 1.2, straetlingite) in variable amounts and ultimately amorphous silica. The
degradation depth of CSH 1.6 corresponds to the depression zone in the pH profile (~4 cm in
50 years). Precipitation of small quantities of other secondary phases (gypsum, sepiolite,
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
gibbsite, burkeite, syngenite) in the external alteration zone of the concrete is also predicted
(Fig. 10). Instead of 0.6 as the reference case, if we assume an initial water saturation of 0.8 in
the concrete, the carbonation process is strongly delayed due to the long induction period
prior to the development of the drying front (Fig. 11). This results in carbonation depths of
~2.5 cm in 50 years (Fig. 11 and 12). The higher pH value (~10) predicted at 50 years for the
initial saturation of 0.8 (Fig. 11) is linked to the precipitation of dawsonite (NaAlCO3(OH)2)
in the external dried zone. This pH buffering is however questionable and disappears if
dawsonite is not included in the scenario. The porosity profiles for the initial liquid saturation
of 0.8 (Fig. 12) show a stronger spatial oscillation with significant opening at the surface
(+30% porosity) and moderate closure (-15 % porosity). All simulations conducted with
stronger initial liquid saturation showed a stronger porosity closure near the carbonation front.
V.C. THICK STRUCTURE/CLAY-STONE TEST CASE
Results for BHP CEM-I structure/clay-stone system are presented for isothermal conditions
(25°C) and for a situation of thermal gradient (40°C at the aerated boundary). Focus will be
given here on evolutions at the internal boundary of the concrete component, near the
ventilated boundary. At the concrete/Geological medium contact (r = 5 m), aqueous
carbonation is involved under control of liquid state diffusion of HCO3- and CO32- dissolved
species (Fig. 13).
Fig. 13 also shows the evolution of liquid saturation profiles at 25°C between 0 and 20 years.
The simulation predicts a significant resaturation of the concrete component by water coming
from the host rock. The competition between pressure gradient from the geological formation
and drying at the internal boundary (r = 3.5 m) leaves a ~5 cm thick fringe on which the
concrete is significantly dried at 20 years. CO2 gas will be able to diffuse rapidly and
carbonates the concrete in this fringe. Simulations predict however complete resaturation of
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
the concrete after ~40 years Calcite/portlandite profiles (Fig. 14) show a carbonation depth of
~4 cm after 40 years (~2 cm after 10 y). Porosity profiles (Fig. 14) show slight oscillations
between 0 and 20 years and stronger spatial variations at 40 y, when the concrete is
resaturated. A marked local minimum (-40 % in porosity) is located at the carbonation front (r
= 3.53 m) whereas a significant opening propagates from the aerated boundary (+25% in
porosity).
The temperature profiles predicted in the 40°C case (Fig. 15) rapidly extend through the entire
concrete/clay-stone system. Temperatures from 40°C to 35°C are seen throughout the
concrete zone. Comparison with the 25°C test-case (Fig. 16) shows that in the 40°C test-case,
the desaturated fringe remains stable at long times, enabling deeper carbonation of the
material. The carbonation depth is ~4.5 cm after 40 years (Fig. 16).
VI. DISCUSSION
The two-phase reactive transport model presented in this work and applied, with 1D
geometry, to simple subsystems representing potential concrete components in ventilated
ILLW disposal cells, gives consistent results: transformation of portlandite and other cement
hydrates to form calcite and various secondary products; the computed pH front matches well
with these transformations. Formation of brines and deposition of salts are predicted in the
parts of the concrete where drying occurs. Note that the sulfate/carbonate salts predicted to
precipitate (syngenite, burkeite) form in limited amounts (locally up to 0.01 vol. fraction) and
were selected by database screening and literature survey (Spencer15), not by experimental
evidence. Predicted porosity variations along the carbonated profile are limited (< ± 10%),
causing a slight opening of the pore space in the outermost zones. Only when the liquid
saturation is strong (> 0.8), the porosity profile displays a local and marked minimum (-50%),
leading to a more marked but less deeper carbonation of the material.
16
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
The progress and extent of these chemical transformations are, however, sensitive to both the
transport and hydraulic properties of the materials (concrete, EDZ, clay-stone). This is why a
generalized form of the Millington-Quirk tortuosity model was implemented and tested to
better match the gas phase diffusion behaviour of concrete. Results obtained on the different
simulation cases reveal that this is necessary but not sufficient to correctly tune the dynamics
of drying, which are coupled to carbonation.
Both carbonation depth and intensity predicted in our work must be considered carefully and
are obviously overestimated. The known protective effect of secondary carbonates will have
to be included in future simulations. This last effect is responsible for the presence of
significant portlandite relicts in carbonated concrete (Thiery16). As a consequence,
carbonation intensity is reduced and a substantial proportion of hydrates remain unaltered in
the carbonated profile and this preserves the mechanical properties of the concrete. In our
description of deeply carbonated concrete, the choice of amorphous silica as prominent and
terminal alteration phase for calcium silicate hydrates is also too crude and does not fit well
with observations, although amorphous silica is indeed found among these phases (Glasser et
al.17, Black et al.18). Improvement in this field will probably come when kinetics of CSH
alteration are better known for low Ca/Si ratio.
Carbonation depths in the order of 0.6 to 1.0 10-3 m y-1 predicted for both configurations, thin
structure aerated on both faces and thick component in contact with clay-stone, are strongly
dependent on the description of the drying process. Gas transport in the partially saturated
material is not a limiting process for carbonation, rather than solid/solution reactions and
(perhaps also) gas/liquid exchanges under low saturation conditions. In situations where the
residual liquid phase occupies specific parts of the porous space (e.g., nanoporosity inside
CSH phases), percolation effects on water exportation and gaseous CO2 ingress are predicted
and will also prevent deep carbonation (Dridi19).
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
Initial saturation conditions of the material is predicted to have a significant influence. In the
case of the thin structure, if it is assumed that the initial saturation of concrete is 0.8 instead of
0.6, then the drying would take ~50 years instead of ~10 years. Fine tuning of the hydraulic
properties attributed to the first mesh cell (in contact with air) of the concrete, will however be
necessary in future computations in order to represent better the drying process. The actual
thickness of the superficial zone, that is rapidly dried out by vapour diffusion and acts as a
suction driver for the internal liquid capillary flow, is probably much thinner than the 5 mm
mesh size adopted in our discretization scheme. Due to this mismatch, that was imposed by
the numerical constraints presented above in § IV.C (Time and space discretization), vapour
diffusion should not actually plays such a significant limiting role as we found in the high
initial saturation runs. As a consequence, the prediction of concrete component resaturation in
the concrete/clay-stone test-case at 25°C (Fig. 13 and 16) should be taken with caution before
such a tuning is done by the examination of experimental data at the relevant scale.
Lower values of the liquid permeability of concrete may also produce a step-wise progression
of the drying front, instead of a behaviour showing rapid percolation of gas through the
sample at some moment. Also, it is known from laboratory tests that carbonation reactions are
limited in a dry material, as soon as liquid saturation is less than ~0,3 (Thiery16). However,
the dependence of chemical reactions on water saturation is presently not included in
TOUGHREACT, and this important effect is also expected to limit significantly the intensity
of carbonation could not be explored.
Eventually, another salient feature of these simulations is related to numerical issues: the use
of the SNIA approach could not be avoided because, in the version of the code we used, gas
transport is not tightly enough coupled to reactions (e.g. between portlandite and dissolved
carbonic acid) occurring between the solid and liquid phases. As a consequence, very small
18
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
time steps had to be used to minimize operator splitting errors. Investigations are presently in
progress to solve this numerical issue.
VII. CONCLUSIONS
Integrated 1D simulations of atmospheric carbonation in concrete components of ILLW
geological disposals during operating period provide a first evaluation of carbonated depth, in
the order of 0.6 to 1.0 10-3 m y-1, in different scenarios of temperature and initial saturation
over a time period of 20 to 100 years. The range of carbonated depth and intensity is however
thought to be overestimated because i) the protective effect of secondary carbonates and the
drop in chemical reactivity of hydrates in dry concrete are not included in the available
numerical model, ii) the description of drying dynamics needs further improvement.
Areas where progress is needed have thus been identified:
- improved combined physical and numerical representation of the two-phase flow boundary
condition at the concrete/air interface which controls the drying dynamics, a key point to
represent correctly the penetration of CO2 into concrete.
- taking into consideration the influence of local liquid saturation on solid/solution reaction
kinetics. This is important for minerals like CSH, which have a complex internal porosity
structure and thus wettability, depending on their composition (Ca/Si ratio).
- evaluating the possibility of improving code performance by coupling more tightly gas
transport and chemical reactions and by parallelizing parts of the numerical algorithm, to gain
at least one order of magnitude in computation speed.
The behaviour of another type of high performance concrete (BHP CEM-V, blended Portland,
fly ash, blast furnace slag cement) is presently evaluated. In addition, sensitivity studies have
also been undertaken on key parameters like permeability and capillary pressure
characteristics.
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
ACKNOWLEDGMENT
K. Pruess, T. Xu, and N. Spycher (Lawrence Berkeley National Laboratory) are gratefully
acknowledged for their help in building and improving the TOUGH scripts and for their
insightful remarks on multiphase physics. A. Burnol and F. Claret (BRGM) have helped us
considerably with databases and script improvement. B. Bary and S. Poyet (CEA/DEN
LECBA) are acknowledged for their help on concrete physics.
REFERENCES
1. ANDRA, “Dossier Argile”, (www.andra.fr) Agence Nationale pour la Gestion des Déchets
Radioactifs, Châtenay-Malabry, France (2005).
2. B. BARY, C. MÜGLER, “Simplified modelling and numerical simulations of concrete
carbonation in unsaturated conditions,” European Journal of Environmental and Civil
Engineering, 9/10, 1049 (2006).
3. B. BARY, A. SELLIER, “Coupled moisture:carbon dioxide-calcium transfer model for
carbonation of concrete,” Cem. Concr. Res., 34, 1859, (2004).
4. M. THIERY, V. BAROGHEL-BOUNY, N. BOURNETON, G. VILLAIN and C.
STEFANI, “Modélisation du séchage du béton. Analyse des différents modes de transfert
hydrique, ” European Journal of Environmental and Civil Engineering, 11/5, 541 (2007).
5. T. XU, E. SONNENTHAL, N. SPYCHER and K. PRUESS, “TOUGHREACT user’s
guide: a simulation program for non-isothermal multiphase reactive geochemical transport in
variably saturated geologic media,” Report LBNL-55460, Lawrence Berkeley National
Laboratory, Berkeley, Calif. (2004).
20
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
6. V. BAROGHEL-BOUNY, M. THIERY, F. Barberon, F., Coussy, O. et Villain G.
“Assessment of transport properties of cementitious materials,” European Journal of
Environmental and Civil Engineering, 11, 671 (2007).
7. R. J. MILLINGTON and J. P. QUIRK, “Permeability of porous solids,” Trans. Faraday
Soc., 57, 1200 (1961).
8. K. PRUESS, C. OLDENBURG and G. MORIDIS, “TOUGH2 user’s guide, version 2.0”,
Technical Report LBNL-43134, California, (1999).
9. M. VAN GENUCHTEN, “A closed-form equation for predicting the hydraulic
conductivity of unsaturated soils”, Soil Sci. Soc. Am. J., 44, 892 (1980)
10. A. LASAGA, “Kinetic theory in the earth sciences”, Princeton University Press,
Princeton, New-Jersey (1998)
11. R. BELARBI, A. AÏT-MOKHTAR, M.QIN and O. OMICRINE “Development of a
simplified approach to model the moisture transfer in building materials”, Revue Européenne
de Génie Civil, 10/9, 1033 (2006)
12. E. GAUCHER et al., “Modelling the porewater chemistry at the Callovo-Oxfordian
formation at a regional scale”, C. R. Geoscience, 338, 917 (2006)
13. E. GAUCHER et al., “Caractérisation géochimique des forages PAC et nouvelles
modélisations THERMOAR”, Technical Report BRGM/RP-54416-FR, BRGM, France,
(2007)
14. J. L. PALANDRI and Y. K. KHARAKA, “A compilation of rate parameters of watermineral interaction kinetics for application to geochemical modelling”, US Geological Survey
Open File Report 2004-1068, Menlo Park, California, USA, (2004)
15. R. J. SPENCER, “Sulfate minerals in evaporite deposits”, in “Sulfate Minerals”, Reviews
in Mineralogy and Geochemistry, 40, 173, edited by Paul H. Ribbe, Min. Soc. Amer. (2000)
21
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
16. M. THIERY, “Modélisation de la carbonatation atmosphérique des matériaux cimentaires.
Prise en compte des effets cinétiques et des modifications microstructurales et hydriques”,
PhD Thesis, ENPC, Marne-la-Vallée, France, (2005)
17. F. P. GLASSER, J. MARCHAND and E. SAMSON, “Durability of concrete –
Degradation phenomena involving detrimental chemical reactions”, Cem. Concrete Res., 38,
226 (2008)
18. L. BLACK, K. GARBEV and I. GEE, “Surface carbonation of synthetic C-S-H samples:
A comparison between fresh and aged C-S-H using X-ray photoelectron spectroscopy”, Cem.
Concrete Res., 38, 745 (2008)
19. W. DRIDI, “Analytical modelling of the coupling between microstructure and effective
diffusivity of cement based materials”, International RILEM Symposium on Concrete
Modelling – CONMOD’08, 26-28 May 2008, Delft, The Netherlands (2008)
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
TABLE CAPTIONS
TABLE I
Concrete and clay-stone physical properties
TABLE II
Clay-stone EDZ physical properties
TABLE III
Mineralogical composition of concrete
TABLE IV
Mineralogical composition of clay-stone
TABLE V
Secondary phases considered in the interaction scenarios
TABLE VI
Kinetic parameters affected to mineral phases. The specific surface area of minerals is set to 1
m2 g-1 except for minerals marked with (*) for which a value of 10 m2 g-1 is fixed. The
oversaturation threshold before precipitation is set to 0 except for phases marked with (**) for
which the threshold is set to 2. This threshold was fixed to 6 for heulandite.
23
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE CAPTIONS
Figure 1: View of the ILLW disposal cell (~10 m diameter). The concrete structure (1 to 2 m
thick) is in contact with the clay host-rock. The cell is progressively filled with waste disposal
packages during operating (after Andra1).
Figure 2: View of the ILLW disposal package. The 1.4 m height container has 0,11 m thick
reinforced walls and contains four primary waste drums (after Andra1).
Figure3: Schematic representation of the interface between concrete and dry air. Main
physico-chemical processes involved in atmospheric carbonation are shown: transport and
flow processes involving gas and liquid phase, dissolution and reaction of CO2,
dissolution/precipitation of minerals. A liquid saturation (Sl) profile is shown (thick line)
together with a pH profile (dotted line). The overshoot in pH is linked with the drying process
which concentrates solutes and leads to brine formation.
Figure 4: Effect of cell size on drying dynamics: evolution of liquid water saturation of the
thin concrete structure in the mesh cell close to the dry air boundary.
Figure 5: Effect of initial liquid water saturation of the cement on drying dynamics. Evolution
of liquid water saturation in the mesh cell close to the dry air boundary) (meshing with x = 5
mm).
Figure 6: Effect of b exponent of Eq. (1) on drying dynamics. Evolution of liquid water
saturation in the mesh cell close to the dry air boundary) (mesh with x = 1 mm).
24
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
Figure 7: Effect of time-step magnitude dt on the spatial distribution of portlandite (BHP
CEM-I, 25°C, 4 years).
Figure 8: BHP CEM-I thin structure case (25°C). Top: Liquid water saturation. Bottom: pH
(along a half section of the structure).
Figure 9: BHP CEM-I thin structure (25°C). Top: Porosity. Bottom: Calcite/portlandite (along
a half section of the structure).
Figure 10: BHP CEM-I thin structure (25°C). Top: CSH phases and amorphous silica.
Bottom: Selected accessory phases (along a half section of the concrete structure).
Figure 11: BHP CEM-I thin structure. Comparison between initial liquid saturations of 0.6
and 0.8. Top: Liquid water saturation. Bottom: pH profiles.
Figure 12: BHP CEM-I thin structure. Comparison between initial liquid saturations of 0.6
and 0.8. (along a half section of the structure). Top: Porosity. Bottom: Portlandite.
Figure 13: Thick concrete structure /Clay-stone case (25°C). Top: Liquid saturation. Bottom:
pH profile. (across the concrete/EDZ region).
Figure 14: Thick concrete structure /Clay-stone case (25°C). Top: Porosity. Bottom:
Calcite/portlandite (across the first 5 cm of aerated concrete).
25
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
Figure 15: Thick concrete structure / Clay-stone case (40°C). Temperature profile at 8 years
Figure 16: Thick concrete structure / Clay-stone case. Comparison between the 25°C and
40°C simulations. Top: Liquid saturation. Bottom: Calcite/portlandite (across the first 5 cm of
aerated concrete).
26
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
TABLE I
BHP
CEM-I
0.13
Porosity
Intrinsic permeability (m2)
Water
9.5 10-20
Gas
8 10-17
2 -1
Effective diffusion (m s )
(Cl-, liquid phase, 25°C) 9 10-12
Bulk claystone
0.18
4.6 10-20
4.6 10-18
2.8 10-11
van Genuchten Pr (Pa)
2 106
1.5 107
van Genuchten n
1.54
1.49
Klinkenberg factor (Pa)
2 105
2 105
Heat conductivity
(Wm-1K-1)
2 (sat.)
1 (dry)
1.2 (sat.)
1.2 (dry)
Heat capacity
(J kg-1 K-1)
908
1050
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
TABLE II
Fractured Microfissured
EDZ
EDZ
0.20
0.18
Porosity
Intrinsic permeability (m2)
Water
9.2 10-17
Gas
9.2 10-15
2 -1
Effective diffusion (m s )
(Cl-, liquid phase, 25°C) 3.6 10-11
9.2 10-19
9.2 10-17
2.8 10-11
van Genuchten Pr (Pa)
2 106
8 106
van Genuchten n
1.5
1.5
Klinkenberg factor (Pa)
2 105
2 105
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
TABLE III
Phase
(volume fraction)
Calcite
Portlandite
CSH 1.6
Monocarboaluminate
Ettringite
Hydrotalcite
Hydrogarnet-Fe
(C3FH6)
Pyrite
Porosity
BHP
CEM-I
0.627
0.050
0.120
0.02
0.031
0.003
0.018
0.13
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
TABLE IV
Phase
(volume fraction)
Calcite
Quartz
Illite
Na-Smectite
Ca-Smectite
Microcline
Kaolinite
Dolomite
Siderite 0.85
Pyrite
Celestite
Porosity
Bulk
clay-stone
0.263
0.185
0.221
0.02
0.04
0.056
0.009
0.012
0.006
0.007
0.0006
0.18
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
TABLE V
Phase type
Phases
Oxides
Magnetite, Amorphous
silica
Hydroxides
Brucite, Gibbsite
Fe(OH)3
Sheet silicates
Sepiolite
Zeolites
Phillipsite K, Phillipsite Ca
Laumontite, Analcime
Gehlenite, Heulandite
Other silicates
CSH 1.2, CSH 0.8
Straetlingite, Katoite_Si
Sulfates,
chlorides and
other
salts
Gypsum, Anhydrite
Burkeite, Syngenite
Glaserite, Arcanite
Glauberite, Polyhalite
Carbonates
Calcite, Nahcolite
Others
Hydrotalcite-CO3
Ettringite, Dawsonite
31
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
TABLE VI
Phases
Analcime(*,**), Heulandite(*), Laumontite (*,**),
Phillipsite,K_alpha (*,**), Phillipsite,Ca_alpha (*,**)
Anhydrite, Arcanite, Burkeite, Dawsonite, Glaserite,
Glauberite, Gypsum, Mirabilite, Nahcolite, Polyhalite,
Syngenite
Brucite, Monosulfoaluminate
C3FH6
Calcite
Célestite
CSH 0.8, CSH 1.2, Katoite silicate, Straetlingite
CSH 1.6, Ettringite, Gibbsite_am, Hydrotalcite, HydrotalciteCO3, Amorphous silica
Dolomite
Ettringite_Fe, Gehlenite
Goethite (*,**)
Iron(III) hydroxide (*)
Illite Mg (*)
Kaolinite (*)
Magnetite,beta
Mg-Montmorillonite-Ca (*,**), Mg-Montmorillonite-Na (*,**)
Microcline
Monocarboaluminate
Portlandite
Pyrite
Quartz (**)
Sépiolite (*, **)
Siderite, Siderite_085
Rate constant
(mol m-2 s-1)
at 298,15 K
1 10-13
Activation
energy
(kJ mol-1)
50
1.6 10-5
20
1.6 10-9
1 10-12
1.6 10-6
1.6 10-6
1.6 10-9
1.6 10-9
20
30
23.4
14.2
50
30
2.95 10-8
1 10-10
1.15 10-10
1.6 10-8
1 10-14
6.6 10-14
1 10-9
3.9 10-15
3.9 10-13
1.6 10-9
1.6 10-8
1 10-8
1 10-14
1.6 10-12
2.95 10-8
52.3
30
86.6
30
50.2
22.2
50
50.2
38.1
10
20
50
87.4
50
52.3
32
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 1
33
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 2
34
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 3
Dry air
(Rh = 40%)
T = 25°C to 40 °C
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NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 4
1,0
Liquid saturation
Fine meshing (1 mm)
0,8
Coarse meshing (5 mm)
0,6
0,4
0,2
0,0
0
20
40
60
80
Time (years)
36
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 5
1,0
Liquid saturation
Sl = 60%
0,8
Sl = 70%
0,6
Sl = 80%
0,4
0,2
0,0
0
10
20
30
40
50
Time 60
(years)
70
37
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 6
1,0
Sl
b = 4,2
0,8
b = 4,0
b = 3,8
0,6
b = 3,4
0,4
0,2
0,0
0
5
10
Time (years)
15
38
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 7
5,0E-02
Volume
fraction
Portlandite profile (4 y)
4,6E-02
dt = 10 s
dt = 20 s
4,2E-02
dt = 200 s
3,8E-02
dt = 400 s
Distance (m)
3,4E-02
0
0,01
0,02
0,03
39
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 8
0.7
BHP CEM-I
Sl
0.6
0y
5y
20 y
0.5
0.4
3y
10 y
0.3
0.2
0.1
Distance (m)
0.0
0
0.01
0.02
0.03
0.04
0.05
0.06
14
pH
13
BHP CEM-I
12
0y
3y
5y
10 y
20 y
50 y
11
10
9
8
Distance (m)
7
0
0.01
0.02
0.03
0.04
0.05
0.06
40
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 9
0.14
0y
20 y
5y
50 y
10 y
BHP CEM-I
0.135
0.13
Porosity
0.125
0.12
Distance (m)
0.115
0
0.01
0.02
0.03
0.04
0.05
0.06
Calcite
Volume fraction
0.16
0.12
0.08
Portlandite
BHP CEM-I
5y
20 y
50 y
0y
0.04
0.00
0
0.01
0.02
0.03
0.04
Distance
0.05 (m) 0.06
41
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
Volume fraction
FIGURE 10
0.12
0.09
BHP CEM-I 50 years
CSH 1.6
CSH 1.2
CSH 0.8
Amorph. Silica
0.06
0.03
0.00
0.01
0.032
0.024
0.02
0.03
0.04
Distance
0.05 (m) 0.06
0.04
Distance
0.05 (m) 0.06
BHP CEM-I 50 years
Volume fraction
0
Gypse
Ettringite
Hydrotalcite
Monocarbo
Sepiolite
0.016
Gibbsite
0.008
0.000
0
0.01
0.02
0.03
42
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 11
Sl
0.7
BHP CEM-I
Init. Sl 0.6
Init. Sl 0.6
Init. Sl 0.6
Init. Sl 0.8
Init. Sl 0.8
Init. Sl 0.8
0.5
0.3
0y
5y
50 y
0y
20 y
50 y
0.1
0
0.01
0.02
0.03
0.04
Distance
0.05 (m) 0.06
14
13
BHP CEM-I
pH
12
11
10
Init. Sl 0.6
Init. Sl 0.6
Init. Sl 0.8
Init. Sl 0.8
9
8
20 y
50 y
20 y
50 y
7
0
0.01
0.02
0.03
0.04
Distance
0.05 (m)
0.06
43
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 12
0.18
BHP CEM-I
Init. Sl 0.6 20 y
Init. Sl 0.6 50 y
0.16
Init. Sl 0.8 20 y
Init. Sl 0.8 50 y
0.14
Porosity
0.12
0.1
0
Distance (m)
0.01
0.02
0.03
0.04
0.05
0.06
0.2
Volume fraction
BHP CEM-I 50 years
0.16
0.12
0.08
Init. Sl 0.6 Calcite
Init. Sl 0.6 Portlandite
0.04
Init. Sl 0.8 Calcite
Init. Sl 0.8 Portlandite
0
0
0.01
0.02
0.03
0.04
Distance
0.05 (m) 0.06
44
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 13
1,0
Sl
BHP CEM-I
0,8
0y
3y
5y
0,6
20 y
0,4
Fractured EDZ Argillites
Concrete
0,2
3,4
3,9
4,4
4,9
Distance
(m)
5,4
5,9
14
BHP CEM-I
13
12
0y
11
20 y
10
9
8
7
pH
6
3.4
3.9
4.4
4.9
Distance
5.4 (m)
5.9
45
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 14
Porosity
0.18
0.16
BHP CEM-I
0y
10 y
20 y
40 y
0.14
0.12
0.1
0.08
3.5
Volume fraction
0.20
3.51
0.16
0.12
3.52
3.53
3.54
Distance
3.55 (m) 3.56
Calcite 10 y
BHP CEM-I
Calcite 40 y
Portlandite 10 y
Portlandite 40 y
0.08
0.04
0.00
3.5
3.51
3.52
3.53
3.54
Distance
3.55 (m) 3.56
46
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 15
45
BHP CEM-I
T (°C)
40
3y
10 y
35
40 y
30
25
0
10
20
Distance
30 (m)
40
47
NUMERICAL SIMULATION OF ATMOSPHERIC CARBONATION OF CONCRETE COMPONENTS IN A DEEP GEOLOGICAL
RADWASTE DISPOSAL SITE DURING OPERATING PERIOD USING TOUGHREACT – L. Trotignon et al. – submitted to Nucl.
Technol.
FIGURE 16
1.0
Sl
25°C 0 y
40°C 5 y
0.8
25°C 20 y
40°C 20 y
25°C 40 y
40°C 40 y
0.6
BHP CEM-I
0.4
0.2
Distance (m)
0.0
3.5
3.51
3.52
3.53
3.54
3.55
3.56
0.20
Volume fraction
BHP CEM-I 40 years
0.16
0.12
25°C Calcite
25°C Portlandite
40°C Calcite
0.08
40°C Portlandite
0.04
0.00
3.5
3.51
3.52
3.53
3.54
Distance
3.55 (m) 3.56
48