REACTIVE TRANSPORT MODELING OF THE INTERACTION BETWEEN WATER AND
1
REACTIVE TRANSPORT MODELING OF THE INTERACTION BETWEEN WATER AND A CEMENTITIOUS GROUT IN A FRACTURE 1 Josep M. Soler, 2 Marja Vuorio, 2 Aimo Hautojärvi 1-Institute of Environmental Assessment and Water Research (IDAEA-CSIC), 08034 Barcelona, Catalonia, Spain 2-POSIVA OY, FI-27160 Eurajoki, Finland Grouting of water-conducting fractures with low-alkali cement is foreseen by Posiva (Finnish nuclear waste management agency) for the potential future repository for high-level nuclear waste in Finland (ONKALO). A possible consequence of the interaction between groundwater and grout is the formation of high-pH solutions which will be able to react with the host rock (gneisses) and alter its mineralogy and porosity. A reactive transport modeling study of this possible alteration has been started following the recommendations from Posiva. CrunchFlow has been used for the calculations. First, the hydration of the low-alkali cement has been modeled using results from the literature as a guide (Fig. 1). The hydrated cement is characterized by the absence of portlandite and the presence of a C-S-H gel with a Ca/Si ratio about 0.8 after tens of years (Ca/Si is about 1.7 in Ordinary Portland Cement). Afterwards, a one-dimensional system simulating the contact between a grouted section of a fracture and the gneiss has been studied (Fig. 2). Diffusion is the only solute transport mechanism in this case. The results from the simulations show a very fast (days to weeks) sealing of porosity at the rock-grout interface. The precipitation of C-S-H, and also ettringite in some cases, is responsible for this fast sealing of porosity. The mixing by diffusion of a high-pH Ca-rich solution from the grout and a Si-rich solution from the rock (plagioclase dissolution) causes this precipitation. Finally, new calculations have simulated the interaction between flowing water and grout and the alteration of the host rock as this alkaline water flows beyond the grouted section of the fracture (Fig. 3). The calculations include the hydration and simultaneous leaching of the grout through diffusive exchange between the porewater in the grout and the flowing water in the fracture. The formation of an alkaline plume is extremely limited when the low-pH grout is used. And even when using a grout with a lower silica fume content the extent and magnitude of the alkaline plume are rather minor. These results are in qualitative agreement with monitoring at ONKALO. (1) HYDRATION OF LOW-ALKALI CEMENT 0 2 4 6 8 10 1.0E-04 1.0E-02 1.0E+00 1.0E+02 t(a) Vol% Alite Belite Aluminate Ferrite C alcite Anhydrite C SH -00 0 5 10 15 20 25 30 1.0E-04 1.0E-02 1.0E+00 1.0E+02 t(a) Vol% Portlandite CSH -1.667 Ettring-Al1.0 Ettring-Al0.8 C SH -04 C SH -08 C SH -10 C SH -12 C SH -14 0 5 10 15 20 25 30 35 2.0E -04 4.0E -04 6.0E -04 8.0E -04 x (m ) V ol% CSH -1.667 SiO 2 (am ) Quartz Biotite Plagioclase Microcline 0 1 2 3 4 5 4.0E -04 5.0E -04 6.0E -04 x (m ) V ol% Portlandite E ttringite T oberm orite Prehnite Ferrite Belite M esolite 0.0E +00 1.0E -02 2.0E -02 3.0E -02 4.0E -02 0.0E +00 2.5E -04 5.0E -04 7.5E -04 1.0E -03 x (m ) C (m ol/kg_H2O) Ca++ M g++ N a+ K+ H C O 3- A l+++ Fe+++ SiO2(aq) SO 4-- Cl- O2(aq) H 2O Si Ca SO 4 + high pH + A l, SO 4 O pen fracture Grout O pen fracture Grout 8.4 8.8 9.2 9.6 10.0 10.4 10.8 11.2 11.6 0.0 0.5 1.0 1.5 2.0 2.5 t(a) pH O N K-KR 3 low pH (2) 1D GROUT-ROCK INTERACTION type calculation (no solute transport). rsible kinetic rate laws for the dissolution of the clinker phases , belite, aluminate, ferrite) and silica fume (CSH-00). equilibrium (fast kinetics) for all the other phases. PRIMARY CEMENT PHASES HYDRATION PRODUCTS final C-S-H gel has a Ca/Si ratio about 0.8. landite only precipitates at early stages and is quickly consumed. ation takes about 100 years to complete and is controlled by the olution of silica fume. er knowledge on the dissolution rates of silica fume could place er constraints on the precise timing and duration of the process. Rock, porosity 5% Rock, porosity 1% Cementitious grout Rock, porosity 5% Rock, porosity 1% 10 mm 10 mm 1 mm CONCEPT MINERAL DISTRIBUTION AT t ≈ 2 days Gout-rock interface at x = 5e-4 m Grout Rock Grout Rock 1D domain •Fast (days) sealing of porosity at the grout-rock interface due mainly to the precipitation of ettringite and tobermorite. •The reaction is driven by the contact between a high-pH Ca-rich solution from the grout and a Si-rich solution (plagioclase dissolution) from the rock. SOLUTE CONCENTRATIONS AT t ≈ 2 days CONCEPT (3) 2D GROUT-ROCK-WATER INTERACTION IMPLEMENTATION 0.5 m 5 m Q 1 ,q 1 Q 2 ,q 2 0.5 m m FR ACTURE PLANE NO RM AL TO FRACTURE PLANE 0.5 m 2 m C alculation dom ain m L 1 1 3 Mixing IN ER T 0.5 m 5 m Q 1 ,q 1 Q 2 ,q 2 0.5 m m FR ACTURE PLANE NO RM AL TO FRACTURE PLANE 0.5 m 2 m C alculation dom ain m L 1 1 3 Mixing INERT GROUT ROCK IN ER T 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 10 .2 11 .0 11 .8 12 .6 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 1 0 .2 1 1 .0 1 1 .8 1 2 .6 norm al lowpH M IXIN G ZO NE M IXIN G ZONE OPEN FRACTURE OPEN FRACTURE GROUT GROUT ROCK ROCK OPEN FRACTURE OPEN FRACTURE 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 10 .2 11 .0 11 .8 12 .6 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 1 0 .2 1 1 .0 1 1 .8 1 2 .6 norm al lowpH M IXIN G ZO NE M IXIN G ZONE OPEN FRACTURE OPEN FRACTURE GROUT GROUT ROCK ROCK OPEN FRACTURE OPEN FRACTURE 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 10 .2 11 .0 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 1 0 .2 1 1 .0 1 1 .8 1 2 .6 normal lowpH 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 10 .2 11 .0 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 7 .8 8 .6 9 .4 1 0 .2 1 1 .0 1 1 .8 1 2 .6 normal lowpH 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 6 .8 7 .2 7 .6 8 .0 8 .4 8 .8 9 .2 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 6 .5 7 .5 8 .5 9 .5 10 .5 11 .5 12 .5 normal lowpH 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 6 .8 7 .2 7 .6 8 .0 8 .4 8 .8 9 .2 0 .1 0 .3 0 .5 0 .7 0 .9 1 .0 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 6 .5 7 .5 8 .5 9 .5 10 .5 11 .5 12 .5 normal lowpH 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 0.0 0.5 1.0 1.5 2.0 2.5 t(a) pH O N K-KR 4 norm al a m m m m L m a L q a L Q / / 32 10 1 1 1000 1 32 / 32 2 3 3 3 1 1 a m m m m L m a L q a L Q / / 32 10 1 1 1000 1 32 / 32 2 3 3 3 2 2 a m m m m L m a L q a L Q / / 32 10 1 1 1000 1 32 / 32 2 3 3 3 1 1 a m m m m L m a L q a L Q / / 32 10 1 1 1000 1 32 / 32 2 3 3 3 2 2 RESULTS Initial groundwater composition (400 m depth): Na-Ca-Cl water I = 0.21 mol/kg_H 2 O pH, t = 1 h pH, t = 0.9 a pH, t = 30 a COMPARISON WITH MONITORING (SHALLOWER BOREHOLES) •Good agreement between model and observations, despite modeling performed with generic parameters (flow, transport, geometries, dimen not intended to simulate exactly the monitoring boreholes and the dif groundwater composition (less saline). Model: mixing zone
description
Rock, porosity 1%. 10 mm. Rock, porosity 5%. 1 mm. Cementitious grout. 10 mm. Rock, porosity 5%. Rock, porosity 1%. REACTIVE TRANSPORT MODELING OF THE INTERACTION BETWEEN WATER AND A CEMENTITIOUS GROUT IN A FRACTURE 1 Josep M. Soler, 2 Marja Vuorio, 2 Aimo Hautojärvi - PowerPoint PPT Presentation
Transcript of REACTIVE TRANSPORT MODELING OF THE INTERACTION BETWEEN WATER AND
REACTIVE TRANSPORT MODELING OF THE INTERACTION BETWEEN WATER AND A CEMENTITIOUS GROUT IN A FRACTURE
1Josep M. Soler, 2Marja Vuorio, 2Aimo Hautojärvi 1-Institute of Environmental Assessment and Water Research (IDAEA-CSIC), 08034 Barcelona, Catalonia, Spain
2-POSIVA OY, FI-27160 Eurajoki, Finland
Grouting of water-conducting fractures with low-alkali cement is foreseen by Posiva (Finnish nuclear waste management agency) for the potential future repository for high-level nuclear waste in Finland (ONKALO). A possible consequence of the interaction between groundwater and grout is the formation of high-pH solutions which will be able to react with the host rock (gneisses) and alter its mineralogy and porosity. A reactive transport modeling study of this possible alteration has been started following the recommendations from Posiva. CrunchFlow has been used for the calculations.
First, the hydration of the low-alkali cement has been modeled using results from the literature as a guide (Fig. 1). The hydrated cement is characterized by the absence of portlandite and the presence of a C-S-H gel with a Ca/Si ratio about 0.8 after tens of years (Ca/Si is about 1.7 in Ordinary Portland Cement). Afterwards, a one-dimensional system simulating the contact between a grouted section of a fracture and the gneiss has been studied (Fig. 2). Diffusion is the only solute transport mechanism in this case. The results from the simulations show a very fast (days to weeks) sealing of porosity at the rock-grout interface. The precipitation of C-S-H, and also ettringite in some cases, is responsible for this fast sealing of porosity. The mixing by diffusion of a high-pH Ca-rich solution from the grout and a Si-rich solution from the rock (plagioclase dissolution) causes this precipitation.
Finally, new calculations have simulated the interaction between flowing water and grout and the alteration of the host rock as this alkaline water flows beyond the grouted section of the fracture (Fig. 3). The calculations include the hydration and simultaneous leaching of the grout through diffusive exchange between the porewater in the grout and the flowing water in the fracture. The formation of an alkaline plume is extremely limited when the low-pH grout is used. And even when using a grout with a lower silica fume content the extent and magnitude of the alkaline plume are rather minor. These results are in qualitative agreement with monitoring at ONKALO.
(1) HYDRATION OF LOW-ALKALI CEMENT
0
2
4
6
8
10
1.0E-04 1.0E-02 1.0E+00 1.0E+02
t (a)
Vo
l%
Alite
Belite
Aluminate
Ferrite
Calcite
Anhydrite
CSH-00
0
5
10
15
20
25
30
1.0E-04 1.0E-02 1.0E+00 1.0E+02
t (a)
Vo
l%
Portlandite
CSH-1.667
Ettring-Al1.0
Ettring-Al0.8
CSH-04
CSH-08
CSH-10
CSH-12
CSH-14
0
5
10
15
20
25
30
35
2.0E-04 4.0E-04 6.0E-04 8.0E-04
x (m)
Vo
l%
CSH-1.667
SiO2 (am)
Quartz
Biotite
Plagioclase
Microcline
0
5
10
15
20
25
30
35
2.0E-04 4.0E-04 6.0E-04 8.0E-04
x (m)
Vo
l%
CSH-1.667
SiO2 (am)
Quartz
Biotite
Plagioclase
Microcline
0
1
2
3
4
5
4.0E-04 5.0E-04 6.0E-04
x (m)
Vo
l%
Portlandite
Ettringite
Tobermorite
Prehnite
Ferrite
Belite
Mesolite
0
1
2
3
4
5
4.0E-04 5.0E-04 6.0E-04
x (m)
Vo
l%
Portlandite
Ettringite
Tobermorite
Prehnite
Ferrite
Belite
Mesolite
0.0E+00
1.0E-02
2.0E-02
3.0E-02
4.0E-02
0.0E+00 2.5E-04 5.0E-04 7.5E-04 1.0E-03
x (m)
C (
mo
l/kg
_H
2O
)
Ca++
Mg++
Na+
K+
HCO3-
Al+++
Fe+++
SiO2(aq)
SO4--
Cl-
O2(aq)
H2O
Si
CaSO4
+ high pH+ Al, SO4
0.0E+00
1.0E-02
2.0E-02
3.0E-02
4.0E-02
0.0E+00 2.5E-04 5.0E-04 7.5E-04 1.0E-03
x (m)
C (
mo
l/kg
_H
2O
)
Ca++
Mg++
Na+
K+
HCO3-
Al+++
Fe+++
SiO2(aq)
SO4--
Cl-
O2(aq)
H2O
Si
CaSO4
+ high pH+ Al, SO4
Open fracture
Grout
Open fracture
Grout
8.4
8.8
9.2
9.6
10.0
10.4
10.8
11.2
11.6
0.0 0.5 1.0 1.5 2.0 2.5
t (a)
pH
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
0.0 0.5 1.0 1.5 2.0 2.5
ONK-KR3low pH
ONK-KR4normal
8.4
8.8
9.2
9.6
10.0
10.4
10.8
11.2
11.6
0.0 0.5 1.0 1.5 2.0 2.5
t (a)
pH
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
0.0 0.5 1.0 1.5 2.0 2.5
ONK-KR3low pH
ONK-KR4normal
(2) 1D GROUT-ROCK INTERACTION
•Batch-type calculation (no solute transport).
•Irreversible kinetic rate laws for the dissolution of the clinker phases (alite, belite, aluminate, ferrite) and silica fume (CSH-00).
•Local equilibrium (fast kinetics) for all the other phases.
PRIMARY CEMENT PHASES
HYDRATION PRODUCTS
•The final C-S-H gel has a Ca/Si ratio about 0.8.
•Portlandite only precipitates at early stages and is quickly consumed.
•Hydration takes about 100 years to complete and is controlled by the dissolution of silica fume.
•Better knowledge on the dissolution rates of silica fume could place better constraints on the precise timing and duration of the process.
Rock, porosity 5%
Rock, porosity 1%
Cementitious grout
Rock, porosity 5%
Rock, porosity 1%
10 mm
10 mm
1 mm
CONCEPT
MINERAL DISTRIBUTION AT t ≈ 2 days
Gout-rock interface at x = 5e-4 m
Grout Rock Grout Rock
1D domain
•Fast (days) sealing of porosity at the grout-rock interface due mainly to the precipitation of ettringite and tobermorite.
•The reaction is driven by the contact between a high-pH Ca-rich solution from the grout and a Si-rich solution (plagioclase dissolution) from the rock.
SOLUTE CONCENTRATIONS AT t ≈ 2 days
CONCEPT
(3) 2D GROUT-ROCK-WATER INTERACTION
IMPLEMENTATION
0.5 m
5 m
Q1, q1
Q2, q20.5 mm
FRACTURE PLANE NORMAL TO FRACTURE PLANE
0.5 m
2 m
Calculation domain
ammmmL
maL
qaLQ // 321011
10001
32 /32 233
3
11
ammmmL
maL
qaLQ // 321011
10001
32 /32 233
3
22
MixingINERT
GROUT ROCKINERT 0.5 m
5 m
Q1, q1
Q2, q20.5 mm
FRACTURE PLANE NORMAL TO FRACTURE PLANE
0.5 m
2 m
Calculation domain
ammmmL
maL
qaLQ // 321011
10001
32 /32 233
3
11
ammmmL
maL
qaLQ // 321011
10001
32 /32 233
3
22
MixingINERT
GROUT ROCKINERT
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
11.8
12.6
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
11.8
12.6
normal low pH
MIXING ZONE MIXING ZONE
OPENFRACTURE
OPENFRACTUREGROUT GROUT
ROCK ROCK
OPENFRACTURE
OPENFRACTURE
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
11.8
12.6
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
11.8
12.6
normal low pH
MIXING ZONE MIXING ZONE
OPENFRACTURE
OPENFRACTUREGROUT GROUT
ROCK ROCK
OPENFRACTURE
OPENFRACTURE
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
11.8
12.6
normal low pH
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
0 .1 0 .3 0 .5 0 .7 0 .9
1 .0
2 .0
3 .0
4 .0
5 .0
6 .0
7 .0
7.8
8.6
9.4
10.2
11.0
11.8
12.6
normal low pH
0 . 1 0 . 3 0 . 5 0 . 7 0 . 9
1 . 0
2 . 0
3 . 0
4 . 0
5 . 0
6 . 0
7 . 0
6 . 8
7 . 2
7 . 6
8 . 0
8 . 4
8 . 8
9 . 2
0 . 1 0 . 3 0 . 5 0 . 7 0 . 9
1 . 0
2 . 0
3 . 0
4 . 0
5 . 0
6 . 0
7 . 0
6 . 5
7 . 5
8 . 5
9 . 5
1 0 . 5
1 1 . 5
1 2 . 5
normal low pH
0 . 1 0 . 3 0 . 5 0 . 7 0 . 9
1 . 0
2 . 0
3 . 0
4 . 0
5 . 0
6 . 0
7 . 0
6 . 8
7 . 2
7 . 6
8 . 0
8 . 4
8 . 8
9 . 2
0 . 1 0 . 3 0 . 5 0 . 7 0 . 9
1 . 0
2 . 0
3 . 0
4 . 0
5 . 0
6 . 0
7 . 0
6 . 5
7 . 5
8 . 5
9 . 5
1 0 . 5
1 1 . 5
1 2 . 5
normal low pH8.4
8.8
9.2
9.6
10.0
10.4
10.8
11.2
11.6
0.0 0.5 1.0 1.5 2.0 2.5
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
0.0 0.5 1.0 1.5 2.0 2.5
t (a)
pH
ONK-KR3low pH
ONK-KR4normal
8.4
8.8
9.2
9.6
10.0
10.4
10.8
11.2
11.6
0.0 0.5 1.0 1.5 2.0 2.5
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
0.0 0.5 1.0 1.5 2.0 2.5
t (a)
pH
ONK-KR3low pH
ONK-KR4normal
0.5 m
5 m
Q1, q1
Q2, q20.5 mm
FRACTURE PLANE NORMAL TO FRACTURE PLANE
0.5 m
2 m
Calculation domain
ammmmL
maL
qaLQ // 321011
10001
32 /32 233
3
11
ammmmL
m
a
LqaLQ // 32
101
1
1000
132 /32 23
3
3
22
MixingINERT
GROUT ROCKINERT 0.5 m
5 m
Q1, q1
Q2, q20.5 mm
FRACTURE PLANE NORMAL TO FRACTURE PLANE
0.5 m
2 m
Calculation domain
ammmmL
maL
qaLQ // 321011
10001
32 /32 233
3
11
ammmmL
m
a
LqaLQ // 32
101
1
1000
132 /32 23
3
3
22
MixingINERT
GROUT ROCKINERT
RESULTS
Initial groundwater composition (400 m depth):
Na-Ca-Cl water I = 0.21 mol/kg_H2O
pH, t = 1 h
pH, t = 0.9 a
pH, t = 30 a
COMPARISON WITH MONITORING (SHALLOWER BOREHOLES)
•Good agreement between model and observations, despite modeling performed with generic parameters (flow, transport, geometries, dimensions) not intended to simulate exactly the monitoring boreholes and the different groundwater composition (less saline).
Model: mixing zone
