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Concrete performance/ deterioration modeling by using thermodynamic
equilibrium codes
Kazuo YAMADA, National Institute for Environmental Studies
Yoshifumi HOSOKAWA, Taiheiyo Cement
2015/07/13 1 JCI-MultiSc_KYamada
Contents 1. Impact of phase composition.
Performances and durability of concrete is determined by hydrates and pore solution chemistry.
2. Basics of reaction transfer. Phase equilibrium, Effective diffusion coefficient, Modeling of
C-S-H.
3. Examples. Behaviors of alkali chlorides Sulfate expansion
4. Required subjects to be clarified. More database on hydrates. Formation factor/ effective diffusion coefficient.
2015/07/13 2 JCI-MultiSc_KYamada
Recent trends of materials for sustainability and durability
SCMs/ addition, blends Limestone Mineral powder Pozzolans Slags Etc. multi-blends
Recycling of wastes as raw meal
Strength and durability of concrete
Pore structure Volume, tortuosity,
constrictivity
Pore solution
chemistry
Hydrates composition
Environmental effects
+
Modification of the nature of cement clinkers and hydrates
2015/07/13 3 JCI-MultiSc_KYamada
New technology requirements
• If pore solution is in an equilibrium with solid phase, geochemical code such as PRHREEQC or GEMS will be useful.
Clinker with
wastes
Blended cement
XRD/Rietveld Image Analysis of BEI/EBSD
Cement hydrates QXRD, IA, Selective dissolution, NMR, TG/DSC, TEM, AFM…
Pore structure pore solution chemistry
Diffusion tests Steady or non-steady Electrical migration…
Squeezing Phase equilibrium
calculation
Solids
Pores
MIP, BET, IA, H-NMR…
2015/07/13 4 JCI-MultiSc_KYamada
Characterization & Modeling
What was the purpose of phase equilibrium calculation by geochemical code?
• Durability is the center of interests for various concrete structures. – An example of nuclear power stations . – OECD/NEA/CSNI CAPS ASCET (Assessment of Structures subject to ConcretE
PaThologies) made a questionnaire for 16 member countries. – According to Neb Orbovic 2014 (OECD/NEA/ASCET – RILEM/ISR Meeting),
followings are the major concerns. – 10/16 ASR (pH) – 5/16 Sulfate attack ([SO4
2-]), Rebar corrosion ([Cl-]/[OH-]) – 4/16 Irradiated concrete, Freeze-thaw, Carbonation (CO2) – 3/16 Chloride interaction ([Cl-])
• Majority is determined by the pore solution and solid chemistry of concrete and they are assumed in some equiliblium.
• Not only one mechanism, but combined degradation is happened. • Then, phase equilibrium calculation is required.
2015/07/13 5 JCI-MultiSc_KYamada
1. Impact of phase composition Ex. 1: Impact of minor limestone powder addition
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Hoshino et al. ACT, 2006
5% of limestone addition increased strength - 10 % for OPC, - 30 % for slag blended cement by the formation of carbonate hydrates.
2015/07/13 JCI-MultiSc_KYamada 7
Hoshino et al. ACT, 2006
2015/07/13 JCI-MultiSc_KYamada 8
D. Helfort, Anna Maria Symp. 2009
OPC Constant W/C
A case of more reactive alumina.
It is possible to reduce 20% of CO2 by optimizing clinker composition and SCMs.
Ex. 2: C/S and pH and ASR expansion
• SCMs suppress ASR expansion. The mechanism has been thought as the decrease in pH by the formation of low C/S C-S-H.
• It will be possible to estimate the effects of SCMs by calculating C/S of C-S-H from the data of QXRD and selective dissolution.
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80
expa
nsio
n ra
tio
SCM replacement level (vol%)
OPCFA(A)FA(B)FA(C)FA(D)BFSBFS
FA(A)
0% 20% 40% 60% 80% 100%
BFS-60%
BFS-50%
BFS-40%
FA(D)-20%
FA(C)-20%
FA(B)-20%
FA(A)-30%
FA(A)-20%
FA(A)-10%
OPC
volume fraction (%)
pore
C-S-H
AFt
Mc
Hc
CH
cement
FA
BFS
Kawabata & Yamada, JSCE 2013
QXRD & selective dissolution. Paste cured at 40 ºC for 28 days.
Mortar bar expansion at 40ºC for 52 weeks. Na2Oeq = 1.2% of cement.
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Direct correlation between estimated [OH-] and ASR expansion
• Different SCMs affect C/S in different ways because of the different natures of them.
• However, it will be possible to estimate [OH-] based on C/S of C-S-H based on many experiments.
• There is a simple positive correlation between [OH-] and ASR expansion.
• Therefore, the calculation of phase equilibrium is fundamental procedure for ASR estimation also.
1
1.2
1.4
1.6
1.8
2
2.2
2.4
0 20 40 60
Ca/
Si m
olar
ratio
SCM replacement level (vol%)
OPC FA(A)FA(B) FA(C)FA(D) BFS
BFS
FA(A)
0
0.5
1
1.5
0.2 0.4 0.6 0.8 1 1.2
expa
nsio
n ra
tio
ca lculated [OH] (mol/l)
OPC FA(A)-10%FA(A)-20% FA(A)-30%FA(B)-20% FA(C)-20%FA(D)-20% BFS-40%BFS-50% BFS-60%
0.2
0.4
0.6
0.8
1
1.2
1 1.5 2 2.5
calc
ulat
ed [O
H] (
mol
/l)
Ca/Si molar ratio of C-S-H gel
OPCFA(A)-10%FA(A)-20%FA(A)-30%FA(B)-20%FA(C)-20%FA(D)-20%BFS-40%BFS-50%BFS-60%
Kawabata & Yamada, JSCE 2013 & unpublished. 2015/07/13 10 JCI-MultiSc_KYamada
2015/07/13 JCI-MultiSc_KYamada 11
Ex. 3: Application of material transport model for life estimation of chloride attack
Many chlorides from sea.
Rebar corrosion
How is it possible to design the service life? How long period survive this structure more?
Harsh environments of chloride attack
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Traditional way for chloride attack
Cl-
Cl-
Cl-
Cl-
Cl- Cl-
Cl-
Cl-
Cl-
Cl-
Inside of concrete Rebar
Assuming Fick’s diffusion law for Cl penetration, Cl concentration at the position of rebar is calculated by using analytical solution of diffusion equation. -> Service life is judged by Cl threshold for corrosion.
2
2
xCD
tC
∂∂
=∂∂
=DtxCtxC s 2
erfc),(
Basic approach in many guidelines
2015/07/13 JCI-MultiSc_KYamada 13
Problems in traditional material transfer model
Sea water
Environments
Cl-
Cl-
Cl-
Cl-
Cl-
Cl- Cl-
Cl-
Cl- Cl-
Cl-
• Assuming homogeneous cement hardened body • Only Cl penetration is considered. • Steel corrosion is basically governed by [Cl-]/[OH-].
[Hardened cement]
Rebar
Degradation = chemical interaction between hydrated cement and ions. However, chemical action = phase equilibrium has not been considered.
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Model considering chemical reaction (phase equilibrium) and multi-species transfer 2. Basics of REACTION TRANSFER
Friedel’s salt AFm Ca(OH)2 C-S-H Caobo-
aluminate
[cement paste] [pore solution]
Sea water Environ.
Material transfer
相平衡
Rebar
SO42- H4SiO4
K+
Al(OH)4- CO3
2-
OH-
Ca2+ Na+
Na+
Mg+
CO2 CO2 moisture H2O
Cl-
Cl-
Cl- Cl-
[gas] Concentration gradient Electrostatic interaction
Phase equilibrium
Transfer
Phase equilibrium
FEM
PhreeqC
Poisson – Nernst – Planck equation
Thermodynamics Combined
This model has been developed by Dr Bjorn Johannesson (now DTU) and Dr Yoshihumi Hosokawa (Taiheiyo Cement Corp.) in middle 2000’.
Hosokawa et al. 2011
2015/07/13 JCI-MultiSc_KYamada 15
Calculation method of material transfer
iiiiii m
xzcB
xxcD
xtc
+
∂∂
∂∂
+
∂∂
∂∂
=∂
∂ φττ
∑=∂∂
iiiw czF
x2
2φε
Nernst – Plank equation
Poisson equation
• i = Ca2+, Cl-, SO42-, Na+, K+, CO3
2-,・・・ • All simultaneous equations are solved by FEM. • Unknown parameters:ci , φ (number of ion species + 1)
Ionic concentration Electrostatic potential
Ionic concentration Electrostatic potential
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Calculation method of phase equilibrium Example: Dissolution equilibrium of Ca carbonate CaCO3 Ca2+ + CO3
2- H2CO3 HCO3
- + H+ CO32- + 2H+
]CaCO[]CO][Ca[
3
23
2
1
−+=K
Solutions of simultaneous equations → Concentrations of each ion,pH,CaCO3 amount
However, in reality, there are many unknown parameters.
• Ion conc.:Ca2+, Al3+, Na+, OH-, SO42-, ・・・
• Hydrates amounts:CSH, Ca(OH)2, AFt, AFm, ・・・
Non-linear multiple simultaneous equations
Numerical calc. software:PHREEQC
→ ←
• Mass action law • Mass balance • Electrical nuetrality
→ ← → ←
]COH[]HCO][H[
32
32
−+=K =3K
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Application of phase equilibrium model to cement system
Na+ K+ Cl− SO42− Ca2+
C-S-H Fr Ms Ett
Al(OH)4−
SiOH
CH
Solution
Solid
Dissolution/ precipitation equilibrium
Speciation of ions
Enable to calculate pore solution composition and hydrates volume in cement paste
• C-S-H → Dissolution equilibrium and C/S variation is reproduced by Nonat’s model (This is the most unique point).
• MS – Fr is modellized by anion exchange reaction.
Ion exchange reaction
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Ca2+
Al3+
SO42-
Ca(OH)2
ettringite AFm
Cl-
Neutralization Sulfate attack DEF
gypsum
Si4+
thaumasite
Acid resist.
Thaumasite Sulfate attack
Chloride attack
pH ASR Na+, K+
CSH Dissolution Heavy metals, nuclides, Organic substances
Environments evaluation
Redox reaction Various species, hydrates, reaction are quantified.
Every degradation can be considered.
Combining material transport and reaction equilibrium
Feature and effectiveness of this model
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Analysis procedure by this combined model
Material cond. Boundary cond. • Chem comp of cement • Mix (W/C,C content) • Porosity, water content • Reaction ratio of minerals
• Ion conc in solution • Partial gas pressure • Analysis period
Input parameters
Initial cond. • Hydrates amounts • Solution amount • Pore amount
Reaction transfer Combined analysis
Ion concentration, hydrates amounts, gas pressure
Analytical results
• Any cement type is acceptable.
• Any environments can be considered.
Phase equilibrium calculation
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Application of phase equilibrium calculation for materials transfer
• Two mechanisms determining transfer should be considered. – Fixation: Ion fixation may delay transfer. – Pore structure: Delayed transfer by complicated pore structure.
Cl Cl
Less permeable More permeable
Pore structure
Cl
Cl Cl
Cl
Fixation
AFm, C-S-H Paste
Pore
Evaluation: Effective diffusion coefficient De from self diffusion coefficient D0 by considering pore structure in dilute solution under high ionic strength calibration.
Small Large Evaluation: Distribution coefficient, binding isotherm
Can be generalized by phase equilibrium model. Problems?
2015/07/13 JCI-MultiSc_KYamada 21
How describe ion fixations of C-S-H with different C/S by phase equilibrium mode?
• What is the mechanism of ion fixation? • Which dissolution equilibrium model should be used?
1. Review of dissolution equilibrium of C-S-H and determination of model should be used.
2. Review of ion fixation by C-S-H and modeling it based on its mechanism.
2015/07/13 JCI-MultiSc_KYamada 22
CaO [mM]
SiO
2 [m
M]
Jennings (1986)
C-S-H dissolution equilibrium model Characteristics of C-S-H dissolution equilibrium
Ca2+
H4SiO4
OH-
C-S-H particle
Pore solution
2015/07/13 JCI-MultiSc_KYamada 23
C-S-H(I)
Invariant point
Invariant point
Jennings (1986)
C-S-H dissolution equilibrium model Characteristics of C-S-H dissolution equilibrium
Ca2+
H4SiO4
OH-
C-S-H particle
Pore solution
0,00
0,50
1,00
1,50
2,00
2,50
0,00 10,00 20,00 30,00 40,00
CaO mmol/l
C/S
Flint and Wells at30°CTaylor at 17-20°C
Lecoq 20°C
Thordvaldson 25°C(+expé sursat)
Modelling of phase equilibrium of C-S-H
Reproduction
Continuous change of Ca/Si
Invariant point
Invariant point
Reproduction of continuous change of Ca/Si
Important point of modelling
2015/07/13 JCI-MultiSc_KYamada 24
C-S-H dissolution equilibrium model Traditional models and their difficult points
• Mainly solid solution model of two end members. –Kulik: Congruent SS between. tobermorite-jennite –Berner: Ingongruent variable end member, Log K depending on C/S
2015/07/13 JCI-MultiSc_KYamada 25
C-S-H dissolution equilibrium model Traditional models and their difficult points
• Load for equilibrium calculation is heavy. Especially for variable Log K. • Poor compatibility with surface potential calculation.
Adopting Nonat’s model not using solid solution concept. [Features of Nonat’s model] •Modelling based on the chemical composition and structure change of C-S-H.
•Surface potential can be calculated.
2015/07/13 JCI-MultiSc_KYamada
C-S-H dissolution equilibrium model Nonat’s model
• Based on 1.1nm tobermolite structure
CaO2 plane →
CaO2 plane →
Si tetrahedra
26
2015/07/13 JCI-MultiSc_KYamada 27
Nonat’s C-S-H model
Si[Q1]
Si[Q2] Non bridging tetrahedron
Si[Q2p] Bridging tetrahedron
Low Ca/Si High Ca/Si
A model based on measurements
29Si solid NMR spectrum of synthesized C-S-H
2015/07/13 JCI-MultiSc_KYamada
28
C-S-H dissolution equilibrium model Nonat’s model
• Based on 1.1nm tobermolite structure
CaO2 plane
Si tetrahedra
CaO2 plane Ca/Si = 0.66 Imaginary composition. C-S-H is not stable less than 0.8 of C/S.
2015/07/13 JCI-MultiSc_KYamada 29
C-S-H dissolution equilibrium model Nonat’s model
• Bridging tetrahedron
Decrease in SiO2 tetrahedra → Increase in Ca/Si
SiO2 tetrahedra →
SiO2 tetrahedra →
CaO2 plane →
CaO2 plane →
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C-S-H dissolution equilibrium model Nonat’s model
• Existing ratio of bridging tetrahedron and variation of Ca/Si
Ca Ca Ca Ca Ca Ca Ca
Ca Ca Ca Ca Ca Ca Ca Ca
Ca Ca Ca Ca Ca Ca Ca Ca
Ca/Si = 0.66
Ca/Si = 0.8
Ca/Si = 1.0 Si OH
Silanol
Negative charge
Negative charge
Negative charge
Si OH
→ + H+ Si O−
Si O−
+ Ca2+ → Si OCa+
Negative charge
Positive charge
2015/07/13 JCI-MultiSc_KYamada 31
C-S-H dissolution equilibrium model Nonat’s model
• Coordinate of Ca2+ on silanol and ζ potential
Ca Ca Ca Ca Ca Ca Ca
Ca Ca Ca Ca Ca Ca Ca Ca
Ca/Si = 1.0
Ca/Si = 1.5 Zero charge
Ca Ca Ca
Zero charge゙
Ca+ Ca+
Ca Ca Ca+ Ca+
Increase in Ca/Si Increase in surface charge
-30
-20
-10
0
10
20
30
0.001 0.01 0.1 1 10 100
[Ca2+] (mmol/l)
potentiel zéta (mV)
2015/07/13 JCI-MultiSc_KYamada 32
-SiOH + Ca2+ -SiOCa+ + H+
-SiOH SiO- + H+
2 -SiOH + Ca2+ -SiOCaOSi- + 2 H+
2 -SiOH + H4SiO4 -SiOSi(OH)2OSi- + H2O
-SiOH + CaOH+ -SiOCaOH + H+
Ca2H2Si2O7 + 4 H+ + H2O 2 Ca++ + 2 H4SiO4
C-S-H dissolution equilibrium model Nonat’s model
K1
K2
K3
K4
K5
K6
Mechanisms mentioned can be summarized in the following six equations.
Installation in phase equilibrium calculation tool ‘PHREEQC’ Ca Ca
Reaction of silanol
Reaction of dimer
2015/07/13 JCI-MultiSc_KYamada 33
Reproduction of phase equilibrium of C-S-H by Nonat’s model
0,000001
0,00001
0,0001
0,001
0,01
0,1
0 0,01 0,02
[CaO] mol/kg
[SiO
2] m
ol/k
g
0,6
0,8
1
1,2
1,4
1,6
1,8
0 0,01 0,02
[CaO] mol/kg
Ca/
Si
[solution composition] [Ca/Si variation]
0,00
1,00
2,00
3,00
4,00
5,00
0,6 1,1 1,6
Ca/Si
Q1/
Q2
[silicate anion chain length]
short
long -10-505
101520253035
0,001 0,01 0,1
[CaO] mol/kg
zeta
(mV
)
Equivalent electric point
2015/07/13 JCI-MultiSc_KYamada 34
Alkali ions fixation by C-S-H
SO4--
Ca++
K+
Na+
Cl-
Cl-
K+
Cl-
C-S-H H+
OH-
Electrical double layer O Ca+
O Ca+
O- O-
Change of composition in EDL
Surface
Zeta-potential measurement of C-S-H suspension
NaCl
Change in surface potential
Phase equilibrium model of C-S-H
Estimation
Verification
Alkali fixation was calibrated by sorption test
2015/07/13 JCI-MultiSc_KYamada 35
0123456789
10
0.5 1 1.5 2
Rd(N
a)
C/S(CSH)
Na100mmol/L
THC_NaCl
Glasser_NaOH
0.1
1
10
100
1000
0.5 1 1.5 2
Rd(N
a)
C/S(CSH)
Na1mmol/LTHC_NaCl
Glasser_NaOH
0 1 2 3 4 5 6 7 8 9
10
0.5 1 1.5 2
Rd(K
)
C/S(CSH)
K 100mmol/L
THC_KCl
Glasser_KOH
0.1
1.0
10.0
100.0
1000.0
0.5 1 1.5 2
Rd(K
)
C/S(CSH)
K 1mmol/LTHC_KCl
Glasser_KOH
Assuming reactions between silanol and alkali, solubility constants are obtained.
C-S-HのCa/Si
Log Kna Log Kk
0.8 −10.8 −9.9 1.0 −11.4 −10.9 1.2 −12.1 −11.9
2015/07/13 JCI-MultiSc_KYamada 36
SiOSi0.5OH + Na+ = SiOSi0.5ONa + H+ Kna SiOH + Na+ = SiONa + H+ Kna SiOSi0.5OH + K+ = SiOSi0.5OK + H+ Kk SiOH + K+ = SiOK + H+ Kk 0.1
1
10
100
0.1 10 1000
Naの
Rd(m
ol/k
g)
初期Na濃度(mM)
0.1
1
10
100
1000
0.1 10 1000
KのRd
(mol
/kg)
初期K濃度(mM)
C/S=1.2
Na (mM)
K (mM)
Rd-
K (m
M)
Rd-
Na
(mM
)
C/S=1.0
C/S=0.8
3.1 Examples - Behaviors of alkali chlorides.
2015/07/13 JCI-MultiSc_KYamada 37
0.0
0.1
0.2
0.3
0.4
0.5
012345678910
0 5 10 15 20
Cs, C
l, N
a, K
(m
ol/k
g)
Ca (
mol
/kg)
Depth (mm)
OPC mortar (CsCl 500mM)
CaCsClNaK
0.0
0.1
0.2
0.3
0.4
0.5
012345678910
0 5 10 15 20
Cs, C
l, N
a, K
(m
ol/k
g)
Ca (
mol
/kg)
Depth (mm)
FAC mortar (CsCl 500mM)
CaCsClNa
0.00
0.10
0.20
0.30
0.40
0.50
0 5 10 15 20
Conc
entr
atio
n (m
ol/k
g)
Depth (mm)
OPC, CsCl=500mM Tot-ClTot-NaTot-KTot-Cs
0.0
0.1
0.2
0.3
0.4
0.5
0 5 10 15 20
Conc
entr
atio
n (m
ol/k
g)
Depth (mm)
FAC, CsCl=500mM Tot-ClTot-NaTot-KTot-Cs
• Cs and Cl ingress to and Na & K leached out in the same depth. • Ingress amount of Cs seems the same with leached amounts of alkalis in mole. • Strong Cs fixation at the surface was caused by the dissolution of Ca. • Cl concentration is higher and this may be caused by the formation of Friedel’s salt.
Effects of concentration and C/S on alkali chloride ingress
2015/07/13 JCI-MultiSc_KYamada 38
05101520253035404550
0.000.010.020.030.040.050.060.070.08
0 5 10 15 20Cl
(m
mol
/kg)
Cs (m
mol
/kg)
Depth (mm)
FAC (3mM CsCl) Cs Cl
0
5
10
15
20
0 5 10 15 20
Conc
. (m
mol
/kg)
Depth (mm)
FAC (3mM CsCl)
Cs Cl
0
5
10
15
20
25
30
0.000.010.020.030.040.050.060.070.08
0 5 10 15 20
Cl (
mm
ol/k
g)
Cs (m
mol
/kg)
Depth (mm)
OPC(3mMCsCl)
Cs Cl
0
5
10
15
20
0 5 10 15 20
Conc
. (m
mol
/kg)
Depth (mm)
OPC(3mMCsCl)
Cs Cl
0.0
0.1
0.2
0.3
0.4
0.5
0.00
0.02
0.04
0.06
0.08
0 5 10 15 20
Cl (
mol
/kg)
Cs (
mol
/kg)
Depth (mm)
OPC (CsCl 500mM)
Cs
Cl
0.0
0.1
0.2
0.3
0.4
0.5
0.00
0.02
0.04
0.06
0.08
0 5 10 15 20
Cl (
mol
/kg)
Cs (
mol
/kg)
Depth (mm)
FAC (CsCl 500mM)
Cs
Cl
• [CsCl] affects fixed amounts but not penetration depth. Nothing of fixation to diffusion. • FA addition reduce penetration depth same for Cs & Cl. Nothing of surface charge on diffusion.
Reproduction by reaction transfer model
2015/07/13 JCI-MultiSc_KYamada 39
0.000
0.005
0.010
0.015
0.020
0.00
0.10
0.20
0.30
0.40
0.50
0 5 10 15 20
Conc
entr
atio
n (M
, Cs,
Cl)
Conc
entr
atio
n (M
, Na,
K)
Depth (mm)
OPC, CsCl=3mM
Tot-Na
Tot-K
0.000
0.005
0.010
0.015
0.020
0.00
0.10
0.20
0.30
0.40
0.50
0 5 10 15 20Co
ncen
trat
ion
(M, C
s, C
l)
Conc
entr
atio
n (M
, Na,
K)
Depth (mm)
FAC, CsCl=3mM
Tot-NaTot-KTot-ClTot-Cs
0.0
0.1
0.2
0.3
0.4
0.5
0 5 10 15 20
Conc
entr
atio
n (m
ol/k
g)
Depth (mm)
OPC, CsCl=500mM
Tot-ClTot-CsTot-NaTot-K
0.0
0.1
0.2
0.3
0.4
0.5
0 5 10 15 20Co
ncen
trat
ion
(mol
/kg)
Depth (mm)
FAC, CsCl=500mM
Tot-ClTot-CsTot-NaTot-K
0
5
10
15
20
0 5 10 15 20
Conc
entr
atio
n (m
mol
/kg)
Depth (mm)
FAC (3mM CsCl)
Cs Cl
0
5
10
15
20
0 5 10 15 20
Conc
entr
atio
n (m
mol
/kg)
Depth (mm)
OPC(3mMCsCl)
Cs Cl
JCI-MultiSc_KYamada 40
3.2 Examples - Sulfate expansion
• Expansion by ASTM C1012
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0 20 40 60 80 100 120
Immersion age (week)
Exp
ansi
on(%
)
OPC OPC+SL (SO3 2.6%) (4.2%)
(5.8%)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0 20 40 60 80 100 120
Immersion age (week)
Exp
ansi
on(%
)
OPC OPC+SL (LS 0%)
(4%)
(8%)
<Effect of Limestone filler> <Effect of SO3 content>
Blast furnace slag suppresses sulfate expansion but limited. Limestone suppresses it much more efficiently. Gypsum addition is also effective. Ogawa et al. 2012
2015/07/13
JCI-MultiSc_KYamada 41
OPC after 38 weeks
OPC+SL after 38 weeks, (expansion:0.301%)
OPC+SL/L4 (SO3=4.2) after 6 years, expansion:0.149%
Expansion by sulfate attack
Ogawa et al. 2012 2015/07/13
JCI-MultiSc_KYamada 42
Calculation results
• OPC
C4FH13
C-S-H
Ca(OH)2
C4AH13MsEttringite
0
50
100
150
200
250
300
350
400
0 7.5 15 22.5 30
Depth from the surface (mm)
Vol
ume
of h
ydra
tes
(cm
3/1L
)
Na+
Ca OH-
: :
SO42-
C4FH13
C-S-H
Ca(OH)2
C4AH13MsEttringite
Gyp
0 7.5 15 22.5 30
Depth from the surface (mm)
1095 days
SO4
Volume
Ogawa et al. 2012 2015/07/13
JCI-MultiSc_KYamada 43
Differences of volume changes and sulfate ingress (1095 days)
C4FH13
C-S-H
Ca(OH)2C4AH13
Monocarbonate
Ettringite
Gyp
0
50
100
150
200
250
300
350
400
0 7.5 15 22.5 30
Depth from the surface (mm)
Volu
me o
f hyd
rate
s (c
m3/1L)
C4FH13
C-S-H
Ca(OH)2
C4AH13
MsEttringite
Gyp
0
50
100
150
200
250
300
350
400
0 7.5 15 22.5 30
Depth from the surface (mm)
Volu
me o
f hyd
rate
s (c
m3/1L)
C4FH13
C-S-H
Ca(OH)2
C4AH13
Ms
Ett
Gyp
0
50
100
150
200
250
300
350
400
0 7.5 15 22.5 30
Depth from the surface (mm)
Volu
me o
f hyd
rate
s (c
m3/1L)
C4FH13
C-S-H
Ca(OH)2
C4AH13
MsEttringite
Gyp
0
50
100
150
200
250
300
350
400
0 7.5 15 22.5 30
Depth from the surface (mm)V
olu
me o
f hyd
rate
s (c
m3/1L)
<OPC>
<OPC+SL(SO3 4.2%)>
<OPC+SL>
<OPC+SL+Lsp>
SO4SO4
VolumeVolumeVolumeVolumeVolumeVolumeVolumeVolume
SO4SO4
SO4SO4
VolumeVolumeVolumeVolume
SO4SO4
VolumeVolumeVolumeVolume
Slag blended Ingress → suppressed (fixing effect on diffusivity) Volume → no effect
Slag blended + SO3 Ingress → suppressed Volume → suppressed (initial Ett formation)
Slag blended + Lsp Ingress → suppressed Volume → suppressed (initial Mc formation)
Ogawa et al. 2012 2015/07/13
JCI-MultiSc_KYamada 44
• Comparison between expansion by ASTM C1012 and estimated volume change of hydrates due to sulfate ingress by calculations
0
5
10
15
20
25
30
35
120% 130% 140% 150% 160%
Volume changes due to sulfate ingressby calculations (%)
Est
imat
ed
tim
e t
o fai
lure
whic
h w
asas
sum
ed
to o
ccur
at 0
.1% e
xpan
sion
by A
STM
C1012 (m
onth
s)
Ogawa et al. 2012 2015/07/13
4. Required subjects to be clarified
• One difficult point of geochemical code is the database of solubility constant for various cement minerals. – Mg-S-H and its atomic scale model. – C-A-S-H and its atomic scale model (partially done by Haas & Nonat, CCR
2014. Amount of Al in C-A-S-H is determined by [Al(OH)4-])
– Description of reactions for above phases and their dissolution coefficients.
• Formation factor/ effective diffusion coefficient. • Reaction speed.
2015/07/13 45 JCI-MultiSc_KYamada
Al in C-S-H
• According to Haas & Nonat, CCR 2014, Al content in C-A-S-H is determined by Al concentration in solution.
• Al concentration is determined by the equilibrium of the system including all phases and ions.
• Once, Al position in C-A-S-H structure and its chemical reaction with solubility constant are described, uptake amount of Al by C-A-S-H will be possible to calculate.
• Then, automatically, the amounts of other Al relating phases and porosity are calculated.
• Finally, strength development, durability/ degradation will be estimated and it will become possible to design sustainable materials and service life of concrete structure quantitatively.
2015/07/13 JCI-MultiSc_KYamada 46
Formation factor/ effective diffusion coefficient
• In many reaction transfer model, pore structure is given as a formation factor measured by some method such as diffusion or migration test, or immersion test. – These tests are basically aimed to evaluate formation factor including the
effects of tortuosity and surface charge (if exists) and others. – No problem in steady state diffusion test. – Problems in electrical migration test.
• One is primary misunderstanding for the consideration of porosity (direct results is not effective diffusion coefficient but required to divide by porosity).
• For the measurement of electric resistance R (inverse of current), the ratio of R(Liquid) to R(Solid), RL/RS is the reducing factor of flux by pore structures.
• In order to obtain effective diffusion coefficient, pore volume must be considered. • De = (RL/RS)D0 (Wrong misunderstanding!) • Second one is the effect of electric migration current under DC and AC method
should be adopted. – Immersion test affected by ion fixation can be used with reverse analysis
assuming diffusion equation considering some non-linear binding. 2015/07/13 JCI-MultiSc_KYamada 47
0( / )e L SR R=J J 0( / ) /e L SD R R D φ=
Problems of electrical migration method
1. Generation of electric immersion current by applying direct voltage. When walls have charges, solution is reversely charged. In this condition, applying direct voltage results in movement of solution = Electroosmotic flow (more current in finer pores).
Solution
Measurement under alternative current
2. Difficult to eliminate the effect of electroosmosis.
+ + + + + + + + + + + - - - - - - - - - - - + + + + + + + + + + + - - - - - - - - - - -
Even in ion exchanging membrane having too small pores for solute diffusion, applying voltage allows movement of ions by ion exchanges. It is difficult to ignore electroosmosis effect when small pores have charges. The effect is more evident under smaller pores and lower electrolyte concentration.
Measurement under infinite concentration of electrolyte solution
+ + + + + + + + + + + - - - - - - - - - - -
+ + + + + + + + + + + - - - - - - - - - - - - + - + - + - + - +- - - - - -
+ - + - + - - - - -
It is required to have electrical neutralization in solution. If not, what happen?
Solution Ichikawa et al. 2013
2015/07/13 48 JCI-MultiSc_KYamada
Sample = sintered plate without surface charge Electrolyte solution = KI (no binding with cement paste)
Correlation with resistance of solution having the same shape: De = 0.0827 D / 0.323 (porosity)
No electroosmosis
Resistance change of a sample containing 0.1M KI kept in 1M KI solution. Dot line is a theoretical calculation based on reference data D ≈1.95x10-9m2/s.
0 1 2 3 40
50
100
150
Time/104s
Res
ista
nce /
Ω
: Observed
: Theoretical (De = 4.99x10−10m2/s)
0 5 10 150
0.05
0.1
0.15
Electric resistance of solution (inverse of KI concentration)
Rat
io o
r R (L
iqui
d/ S
olid
) (in
vers
e of
cur
rent
=
Diff
usio
n in
Sol
id/ L
iqui
d)
Ichikawa et al. 2013 2015/07/13 49 JCI-MultiSc_KYamada
Mortar plate (W/C = 0.55, S/C=3)
Higher resistance ratio of solid (less current) in less resistance of KI solution (higher concentration) Correlation with resistance of solution having the same shape:
De = 0.00224 D / 0.189 (porosity) Significant electroosmotic flow!!
Resistance change of a sample containing saturated Ca(OH)2 solution kept in 1M KI solution. Dot line is a theoretical calculation based on reference data D ≈1.95x10-9m2/s (electoosmotic flow was ignored)
0 10 20 30 400
200
400
600
Time/104s
Res
ista
nce
/ Ω
: Observed
: Theoretical (De = 0.231x10−10m2/s)
0 5 100
0.01
0.02
2015/07/13 50 JCI-MultiSc_KYamada
Ichikawa et al. 2013
Interaction delays diffusion? • Cl penetration seems free from Cl concentration. • Fixation ability only changes total Cl concentration. • When the rate of fixation reaction such as ion exchange of
AFm to Friedel’s salt is not fast enough although that is the basic assumption of reaction transfer, fixation may not affect diffusion so much.
2015/07/13 JCI-MultiSc_KYamada 51
0
0.2
0.4
0.6
0.8
1
0 10 20 30
Cl conc(p
aste
%)
Distance from surface(mm)
12month
24month
36month
0
0.2
0.4
0.6
0.8
1
0 10 20 30
Cl conc(p
aste
%)
Distance from surface(mm)
0
0.2
0.4
0.6
0.8
1
0 10 20 30C
l conc(p
aste
%)
Distance from surface(mm)
Concrete Block, W/C=0.50, Sea shore exposure at 22ºC (annual average) OPC FA15% FA25%
Conclusions
• Impacts of phase composition on the performance and durability and importance of phase equilibrium calculation were introduced.
• Basics of reaction transfer model composed of phase equilibrium calculation based on PHREEQC and multi-species transfer based on Nernst-Plank equation were summarized.
• Unique description of C-S-H for continuous change in C/S based on Nonat’s crystal model was explained.
• Examples of application of reaction transfer calculation for alkali chloride behaviors and sulfate expansion were introduced.
• Required subject to be clarified such as further modeling of M-S-H, C-A-S-H, formation factor/ effective diffusion coefficient determination, fixation rate.
2015/07/13 JCI-MultiSc_KYamada 52