Post on 04-Jun-2022
1Materials Science & Technology
Barbara Lothenbach1, Erich Wieland2, B. Schwyn3,
R. Figi1, D. Rentsch1
1 Empa, Laboratory for Concrete & Construction Chemistry, Switzerland 2 PSI, Laboratory for Waste Management, Switzerland
3 Nagra, National Cooperation for the Disposal of Radioactive Waste, Switzerland
Hydration of “low pH” cements
2Materials Science & Technology
Objectives
�Hydration of
� OPC: CEM I 42.5 HS
� ESDRED:
CEM I 42.5 N + 40% silica fume + accelerator
� LAC: CEM III/B 42.5 L + 10% nanosilica
Cementitious materials used in field experiments
- composition of the pore solution- mineral composition of the cement matrix
- comparison
3Materials Science & Technology
Cement-Clay interface
Borehole 1 (350 mm)
EDZ
OPA
LAC
ESDRED
OPC
Side view Top view
Cement
OPA
4Materials Science & Technology
OPC: CEM I 42.5 R HS(g/100g)
CaO 58.8 alite 31
SiO2 20.6 belite 36
Al2O3 3.9 aluminate 1.6
Fe2O3 5.2 ferrite 16
MgO 4.6 MgO 4.6
Na2O 0.27 CaCO3 3.1
K2O 0.75 CaSO4 5.1
CO2 1.4 Na2O 0.22
SO3 3.5 K2O 0.27
CaOfree 0.71 Na2SO4 0.12
LOI 2.3 K2SO4 0.89
w/c = 0.8
5Materials Science & Technology
clinker
Hydration (Lothenbach and Winnefeld, 2006)
clinker
EttringitePortlanditeC-S-Halite (C3S), belite (C2S)
aluminate(C3A), ferrite C4AF)
6Materials Science & Technology
All parameters (Ki, Ni) from
Parrot and Killoh (1984)
Modeling - Dissolution
( )( )( )
( )( )
( ) 3
1
1
11
1
)1ln(1
3
3/1
3/22
1
1
1
Ntt
t
tt
Nttt
KR
KR
N
KR
α
α
α
αα
−×=
−−
−×=
−−−= −
Empirical Approach: Parrot and Killoh (1984)
g/1
00 g
0
10
20
30
40
50
60
70
0 0.1 1 10 100time (days)
//
alite: C3S
ferrite:C4AF
belite: C2S
aluminate:C3A
Cement specific input: surface area, w/c
α: degree of hydration
7Materials Science & Technology
K2SO4
Na2SO4
hemihydrateCaO
Thermodynamic Modeling
C3S C2S C3A C4AF
Cements
I clinkers (slowly soluble)
II soluble solids
gypsumanhydrite
calcite
K2ONa2OMgO
III water
H2O
Ettringite
Portlandite
C-S-H
AFm
Hydrotalcites, ...
Ca2+
CaOH+ Speciation in solutionCaSO4
0
Thermodynamic modeling
8Materials Science & Technology
Modeling – Volume of solids
0.01 0.1 1 10 100 1000
0
10
20
30
40
50
60
C2S
C4AF
gypsum
hydrotalcitecalcite
ettringite
monocarbonate
portlandite
C-S-H
C3S
cm
3/1
00 g
cem
ent
time [days]
9Materials Science & Technology
ESDRED: 60% CEM I + 40% silica fume5% alkali free accelerator
CEM I 42.5 N silica fume alkali-free(g/100g) accelerator
CaO 61.6 2.1 <
SiO2 21.9 93.3 <
Al2O3 4.8 0.2 16
Fe2O3 2.5 0.1 <
MgO 1.9 0.4 0.7
Na2O 0.25 <0.01 0.2
K2O 0.99 0.5 0.5
CO2 2.0 -- --
SO3 3.4 0.02 15
LOI 2.3 3.1
dissolved organic carbon 2.5
→ 0.16 mmol
→ 0.18 mmol
+ CaSO4 (0.32)+ CaO (0.64)→ C6A$3H32
10Materials Science & Technology
0
500
1000
1500
2000
2500
3000
3500
4000
5 10 15 20 25 30 35
2-theta / °
co
un
ts /
-
360 days
56 days
7 days
1 day
1 h
unhydrated
Ettringite
E E
Alite/
belite
FG A
EE
Anhydrite
E
C 3 A
Hemicarbonate
1-56 days Portlandite
1-7 daysMono-
carbonate
Hemi-
carbonate
Alite
C-S-H
XRDA + $ + 2C$ + 4C -> C6A$3H32
11Materials Science & Technology
TGA
50
55
60
65
70
75
80
85
90
95
100
0 100 200 300 400 500 600 700 800
temperature (°C)
rela
tiv
e w
eig
ht
(%)
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
Dif
f. r
ela
tiv
e w
eig
ht
(%/K
)
unhydrated
1 hour
2 hours
4 hours
6 hours
1 day
2 days
4 days
7 days
14 days
28 days
56 days
210 days
360 days
ESDRED
C-S-H
CaCO3
ettringite
hemicarbonate
1-56 days
max. 4 days
unhydrated
1 h
7days
7 days1 h
unhydrated
360 days
360 days
210 days
14 days
4 days2 days
1 day
portlandite
1-14 days
max. 4 days
gypsum
12Materials Science & Technology
Reactivity of SiO2
� Si-NMR
Silica fume Q4
anhydrouscement Q0
Q1Q2
13Materials Science & Technology
Si NMR
dissolution of silica fume
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0.01 0.1 1 10 100 1000
time [days]
sil
ica f
um
e [
g/1
00 g
]
initial amount of silica fume
14Materials Science & Technology
Si NMR
dissolution of silica fume
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0.01 0.1 1 10 100 1000
time [days]
sil
ica f
um
e [
g/1
00 g
]
initial amount of silica fume
SiO2 [%]= 17 + 23e-0.05t
15Materials Science & Technology
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
0.01 0.1 1 10 100 1000Time (days)
mo
l/l
K
Na
S
OH-
Ca
Si
Al
DOC
Composition of the pore solution
16Materials Science & Technology
ESDRED (CEM I 42.5 N + SF + Sigunit)
0
0.05
0.1
0.15
0.2
0.25
0.01 0.1 1 10 100 1000Time (days)
mo
l/l
Al
Ca
K
Na
OH
S
Si
K
Na
S
OH-
Ca
SiAl
pH (360 days)11.3
Composition of the pore solution
K, Na => in C-S-HLow C/S => more K, Na in C-S-H
17Materials Science & Technology
alkali uptake
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0.01 0.1 1 10 100 1000
sil
ica f
um
e [
g/1
00 g
]
0
50
100
150
200
250
300
350
400
Na +
K [
mM
]
silicafume
Na + K
initial amount of silica fume
18Materials Science & Technology
dissolution of silica fume
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0.01 0.1 1 10 100 1000
time [days]
sil
ica f
um
e [
g/1
00 g
]
11.0
11.5
12.0
12.5
13.0
13.5
pH
silicafume
pH
initial amount of silica fume
19Materials Science & Technology
Modeling ESDRED hydration
Portland cement hydration
• similar to OPC system• 1st hour increased dissolution of clinker
(Paglia et al., 2004; XRD)• silica fume dissolution according to NMR data
decreases at low pH values
Problems
� Alkali (K) and Al-uptake in C-S-H not well known� strätlingite or Al-in C-S-H?
EDS: 0.08 Al/Si in C-S-H
20Materials Science & Technology
Experimental:
Portlandite 1-7 days
Hemi-/Monocarbonate: 1-28 days
Modeling - relative mass of solids(mass refers to total solid, including hydrated)
pH > 13 pH ≤ 12.5
pH 11.3
1E-3 0.01 0.1 1 10 100 1000
0
5
10
15
20
25
30
35
40
45
50
silica fume
aluminateferrite
alite
pore solution
belite
calcite hydrotalcite
ettringite
monocarbonate
portlandite
C-S-H
unhydrated clinker
g/1
00 g
cem
ent hydra
ted
time (days)
21Materials Science & Technology
0.01 0.1 1 10 100 1000
0
5
10
15
20
25
30
35
40
45
50
55
silica fume
C3A
C2S
C4AF
hydrotalcite
calcite
ettringite
monocarbonate
portlandite
C-A-S-H
C3S
cm
3/1
00 g
cem
ent
time [days]
Modeling – Volume of solids
Al/Si = 0.08C-(Al)-S-H
hydrotalcite
calcite
11
11.5
12
12.5
13
13.5
pH
pH measured
22Materials Science & Technology
0.01 0.1 1 10 100 1000
0
5
10
15
20
25
30
35
40
45
50
55 strätlingite
silica fume
thaumasite
C3A
C2S
C4AF
hydrotalcitecalcite
ettringite
monocarbonate
portlanditeC-A-S-H
C3S
cm
3/1
00 g
cem
ent
time [days]
Modeling – Volume of solids
Al/Si = 0.08C-(Al)-S-H
11
11.5
12
12.5
13
13.5
pH
pH measured
thaumasite
23Materials Science & Technology
-1
-0.5
0
0.5
1
0.01 0.1 1 10 100 1000time (days)
effe
ctive
sa
tura
tio
n in
de
x
portlandite
ettringite
-1
-0.5
0
0.5
1
0.01 0.1 1 10 100 1000time (days)
effe
ctive
sa
tura
tio
n in
de
x
portlandite
ettringite
thaumasite
ionsofnumbern
K
IAP log
n
1
index saturation eff
S0
=
=
Thaumasite formation possible
24Materials Science & Technology
0.01 0.1 1 10 100 1000
0
5
10
15
20
25
30
35
40
45
50
55 Al(OH)3
silica fume
gypsum
C3A
C2S
C4AF
hydrotalcite
calcite
ettringite
monocarbonate
portlandite
C-S-H
C3S
cm
3/1
00 g
cem
ent
time [days]
Strong dependency on silica fume dissolutionModeling – Volume of solids
10
10.5
11
11.5
12
12.5
13
13.5
pH
ESDRED
ESDRED
silica fume reacted
Al/Si = 0.08C-(A)-S-Hportlandite
Calcite
gypsum
hydrotalcite
25Materials Science & Technology
� Mix of OPC with SiO2
� 0-2 days: similar to OPC
� >2 days: SiO2:
� no (temporary small amount) portlandite – low pH buffering capacity
� pH decreases, no further SiO2 reaction
� Hydration products
� C-S-H (low C/S), ettringite
� hydrotalcite, calcite, hemi-/monocarbonate
� pH decreases with time (11.3 after 1 year)
� Solution dominated by Ca, K, Na, OH, DOC
� Longterm unclear (ettringite <-> thaumasite ?)
� potential for stratlingite, Si-hydrogarnet or thaumasite
Summary - ESDRED
26Materials Science & Technology
Portland cement slag Nanosilica
(g/100g)
CaO 66 41
SiO2 17 36 >99.8
Al2O3 4 12
Fe2O3 3 0.3
MgO 5 7
Na2O 0.1 0.3
K2O 1 0.3
CO2 1.7 0.01
SO3 3.2 0.8 (as S(-II))
LOI 0.7
w/b = 1.1
LAC: 90% CEM III/B + 10% Nanosilica
(contains ~74% slag)
27Materials Science & Technology
XRD
0
500
1000
1500
2000
2500
3000
3500
4000
5 10 15 20 25 30 35
2-theta / °
co
un
ts /
-
Hemicarbonate
> 1 dayC-S-H
1 h
1 day
7 days
56 days
360 days
unhydrated
Ettringite
E E
Alite/
belite
EE
C
gypsum
E
C 3 A
Mono-
carbonate
Alite
28Materials Science & Technology
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800
temperature [°C]
rela
tiv
e w
eig
ht
[%]
-0.18
-0.12
-0.06
0.00
0.06
0.12
0.18
Dif
f. r
ela
tive
we
igh
t [%
/K]
unhydrated
1 hour
2 hours
6 hours
1 day
2 days
7 days
28 days
56 days
210 days
360 days
LAC
C-S-H
CaCO3
ettringite
hemicarbonate
unhydrated
6 h
7days
1 day
1 h
unhydrated
360 days
210 days
2 days
1 day
1 h
gypsum
Ettringite
TGA
No portlanditeAFm
29Materials Science & Technology
Si NMR
dissolution of nanosilica
0%
5%
10%
15%
20%
25%
0.01 0.1 1 10 100 1000
time [days]
nan
osil
ica [
g/1
00]
initial amount of nanosilica
NS = 0.1*10-0.25*t
30Materials Science & Technology
Selective dissolution with EDTA
dissolution of slag
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.01 0.1 1 10 100 1000
time [days]
sla
g [
g/1
00 g
un
hyd
rate
d L
AC
]
initial slag content of LAC
slag [%]= 51 - 8*log(time)
31Materials Science & Technology
LAC: CEM III/B 42.5 L + Nanosilica
0.000001
0.00001
0.0001
0.001
0.01
0.1
1
0.01 0.1 1 10 100
Time (days)
mo
l/l
SO4
HS-
KNa
OH-
Ca
SiAl
Composition of the pore solution
OPC slagnano silica
32Materials Science & Technology
LAC: CEM III/B 42.5 L + Nanosilica
0.0001
0.001
0.01
0.1
0.01 0.1 1 10 100 1000
Time (days)
mo
l/l
SO4
Stot
HS-
S2O3
SO3
S2O3
detection limit
SO4
SO3
Sulfur speciation
33Materials Science & Technology
Modeling LAC hydration
Portland cement hydration
• according to OPC system• nanosilica dissolution according to NMR data
• slag dissolution according to selective dissolution
Problems� Alkali (K) and Al-uptake in C-S-H not well known
� strätlingite or Al-in C-S-H?
34Materials Science & Technology
LAC modelled
Al/Si = 0.08
0.01 0.1 1 10 100 1000
0
5
10
15
20
25
30
35
40
45
50
55
C-A-S-H
stratlingite
nanosilica
unhydrated clinker
hydrotalcite
calcite
ettringite
gypsum
slag
cm
3/1
00 g
cem
ent
time [days]
35Materials Science & Technology
Effective SI
-1
-0.5
0
0.5
1
0.01 0.1 1 10 100 1000time (days)
effectiv
e s
atu
ratio
n in
dex
portlandite
ettringite
thaumasite
strätlingite
-1
-0.5
0
0.5
1
0.01 0.1 1 10 100 1000time (days)
effe
ctive
sa
tura
tio
n in
de
xOPC
LAC
ESDRED
36Materials Science & Technology
� Slag with OPC and SiO2
� 0-1 days: similar to OPC,
� >1 days: slag + SiO2: � Reducing conditions (HS-)
� no portlandite
� pH decreases
� Main hydration products� C-S-H (low C/S), ettringite -> strätlingite?
� pH decreases with time (12.3 after 1 year)
� Solution dominated by Ca, K, Na,OH and HS--
Summary - LAC
37Materials Science & Technology
Comparison: hydrates after 1 year
0
500
1000
1500
2000
2500
3000
3500
4000
5 10 15 20 25 30 35
2-theta / °
co
un
ts /
-
C-S-H
ESDRED
LAC
OPC
Ettringite
EE
alite/
belite
E
E
CE
portlandite
portlandite
alite
portlanditemonocarbonate
ferrite
38Materials Science & Technology
Comparison: different pore solutions
pH values
11
11.5
12
12.5
13
13.5
0.01 0.1 1 10 100 1000
time (days)
pH
OPC
CEM I HS
ESDRED:
60% CEM I
40% silica fume
accelerator
LAC
90% CEM III/B
10% nanosilica
39Materials Science & Technology
Comparison: main phases
OPC LAC ESDREDESDRED
40Materials Science & Technology
pH
OPC LAC ESDRED
41Materials Science & Technology
Conclusions
� OPC- hydration consistent with previous hydration studies - pH = 13.3 after 12 months
� ESDRED (CEM I + 40 % SiO2)- Initially similar to OPC - Silica fume dissolution proceeds slowly
- C-S-H: Initially C/S ~ 1.5, after 10 days ↓ (final C/S ~ 0.9)- Portlandite consumed after 10 days
- Alkali and pH ↓ (after 12 months: pH = 11.3)
� LAC (CEM III/B + 10% SiO2)- Initially similar to OPC - HS- increases with time – reducing conditions- pH = 12.3 after 12 months
42Materials Science & Technology
Conlcusion 2: SCM
� Reactivity of slag, silica fume
-> depends on hydrate assemblage
� Al and alkali uptake in C-S-H !
� No portlandite, strätlingite formation
� Thaumasite formation possible
� Thermodynamic models for
Al-alkali-C-S-H missing