Effect of SCMs on hydration kinetics of cementitious systems
Transcript of Effect of SCMs on hydration kinetics of cementitious systems
International Summit on Cement Hydration Kinetics 1
Ecole Polytechnique Fédérale de Lausanne
Swiss Federal Institute of Technology in Lausanne
Effect of SCMs on hydration kinetics
of cementitious systems
Laboratory of Construction Materials
Vanessa KOCABA and Karen SCRIVENER
International Summit on Cement Hydration Kinetics 2
↓ CO2
Cement industry
Clinker
Natural pozzolanSilica fumeFly ash
Process optimisation ↓ clinker factor
Gypsum Cement
SCMs
same or higher performance
[Hogan et al., 1981]
40% slag
No slag
Slag
Effect of SCMs on hydration and microstructure
Introduction
International Summit on Cement Hydration Kinetics 3
OPC + water C-S-H + CH + other hydrates
Hydraulic reaction
Pozzolanic reaction
Pozzolan + CH + water C-S-H + other hydrates
Rate influenced by:
Surface area: fine
pozzolan (e.g. silica fume)
react more rapidly
Glass composition:
high-calcium fly ash reacts
more quickly
Temperature
pH: glass phases are
more soluble at high pH
and reacts more quickly.
Strong influence of the
concentration of alkalis
More space available
More surface for C-S-H
precipitation
CH
CH
Definitions-Hydraulic & pozzolanic reactions
Mainly responsible for strength
Impermeability of concrete
More strength
slag + water C-S-H + other hydrates
Reactions where water is combined increase the solid volume, fill pores, increase strength
International Summit on Cement Hydration Kinetics 4
SiO2
Portland Cement
Al2O3CaO
Slag
Fly Ash
C
Natural pozzolan
SilicaFume
Limestone
Metakaolin
F
Chemical composition of various SCMs
Definitions-Hydraulic & pozzolanic reactions
International Summit on Cement Hydration Kinetics 5
IncreasingCalciumContent
Nature of the reaction of different SCMs
Pozzolanic effect Hydraulic effect
Silica fume
Type F-Fly ash-Low CaO
Fly ash-Medium CaO
Type C Fly ash-High CaO
Slag
Metakaolin, clay
Cement
Definitions-Hydraulic & pozzolanic reactions
International Summit on Cement Hydration Kinetics
Impact of SCMs on Hydration
Impact of SCM on Hydration of Cement:
FILLER EFFECT
1. more space due to dilution by SCM
2. Surface acts as nucleation site for hydrates
As most SCM react little in the first day these effects can be studied by calorimetry
Reaction of SCMs themselves
Measurement is the big issue
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International Summit on Cement Hydration Kinetics
FILLER EFFECT 1 – particles similar size to cement grains
Cement with and without 30% fine ground quartz
(d50=15 µm) (assumed non reactive),
7
Heat
evolu
tion
time 1 day 20 days
Cum
ula
tive h
eat
referencewith 30% quartz
Thesis Rodrigo Fernadez 2009normalised by cement content
International Summit on Cement Hydration Kinetics
FILLER EFFECT 1 – particles similar size to cement grains
8
Heat
evolu
tion
time 1 day 20 days
Cum
ula
tive h
eat
Acceleration part not affected:minimal influence of quartz surface on nucleation and growth
Time to peak extended,
more space for hydrates delays onset
of decceleration
Enhancement of cement hydration
Typically +5%At long ages
Thesis Rodrigo Fernadez 2009
International Summit on Cement Hydration Kinetics 9
0 5 10 15 20 25 30 35 40 45 500
1
2
3
4
5
6
7
100% Cement
90% Cement-10% SF
Heat
(mW
.g-1 o
f cem
en
t)
T ime (hours)
SCM acts as nucleation sites for C-S-H growth
FILLER EFFCT 2 – fine particles, silica fume
Enhances kinetics in acceleration period
surface for nucleation
[V.Kocaba, 2008]
International Summit on Cement Hydration Kinetics
Isothermal calorimetry
Filler effect?Influence of slagon clinker reaction:-Enhancement of hydration evolution of C3S -Impact on aluminatephases
International Summit on Cement Hydration Kinetics
Isothermal calorimetry
Filler effect?Influence of slagon clinker reaction:-Enhancement of hydration evolution of C3S -Impact on aluminatephases
International Summit on Cement Hydration Kinetics
Isothermal calorimetry
Filler effect?Influence of slagon clinker reaction:-Enhancement of hydration evolution of C3S -Impact on aluminatephases
International Summit on Cement Hydration Kinetics
Phase assemblage: model cement properly sulfated
P 92/8_ 4.1G
International Summit on Cement Hydration Kinetics
Phase assemblage: model cement properly sulfated
M 92/8_ 4.1G
International Summit on Cement Hydration Kinetics
Impact of slag
Small evidence of filler effect 1 (extra space)
No evidence of extra nucleation, filler effect 2
Large evidence of “aluminate” reaction
– varies with cement type
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International Summit on Cement Hydration Kinetics
Effect of slag on cement hydration at early ages
0 10 20 30 40 50 60 70 800.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5N
orm
ali
sed
heat
(mW
.g-1of
cem
en
t) B
B-S1
B-S1-1% Gypsum
B-S1-2% Gypsum
B-S1-3% Gypsum
B-S1-4% Gypsum
Time (hours)
Calorimetry with Gypsum addition to separate peaks
International Summit on Cement Hydration Kinetics
0 10 20 30 40 50 60 70 800,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5N
orm
ali
sed
hea
t
(mW
.g-1of
cem
ent)
B-S1-2% Gypsum
Time (hours)
Aluminate from cement?Or from slag?
Silicate
Effect of slag on cement hydration at early ages
Calorimetry with Gypsum addition to separate peaks
International Summit on Cement Hydration Kinetics
Effect of slag on cement hydration at early ages
0 10 20 30 400
1
2
3
Time (hours)
Heat
(W
.kg
-1)
Corundum
Rutile
Quartz
[Le Saout, Ibausil, 2006]
Filler effect
Filler effect also with other powders
International Summit on Cement Hydration Kinetics
Additions have different effects on the nucleation of the
calcium silicate and calcium aluminate hydrates.
Most additions seem to have minor impact on calcium
silicate nucleation and growth (exception is silica fume)
Nearly all fillers seem to have a major influence on second
reaction period of aluminates
(maybe by affinity to absorb sulfate)
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International Summit on Cement Hydration Kinetics
Measurement of degree of reaction
Vanessa Kocaba, CP4
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International Summit on Cement Hydration Kinetics
How to measure the reactivity of slag
• Selective dissolution
• Recrystallisation by DSC
• SEM-Image analysis on BSE and
mapping
• Isothermal calorimetry
• Chemical shrinkage
International Summit on Cement Hydration Kinetics
A -S8 1 day 71.6 ± 1.8 -79.0 ± 4.4 63.5 ± 4.4
B-S8 1 day 66.5 ± 1.8 -66.3 ± 4.6 76.2 ± 4.6
C-S8 1 day 65.2 ± 5.8 -63.1 ± 14.6 79.4 ± 14.6
A -S8 90 days 72.8 ± 4.2 -82.0 ± 10.5 60.5 ± 10.5
B-S8 90 days 77.4 ± 3.5 -93.5 ± 8.8 49.0 ± 8.8
C-S8 90 days 70.1 ± 4.0 -75.1 ± 9.9 67.4 ± 9.9
Samples
U ndissolved
materials
(%)
(%init ial slag-%undissolved materials)
%init ial slag
D egree of hydrat ion of slag
[Luke et al., 1987]
Corrected
Selective dissolution: results
Remaining undissolved phases of cement
(even after some modifications of the procedure)
Position [°2 CuKα]
10 20 30 40 50 60
Ca
lcit
e +
C-S
-H
C2S
C2S
C2S
CH
CH
CH
CH
CH
CHC
alc
ite
C2S
C2S
Cement B 90 days
C2S
Ca
lcit
e +
C-S
-H
C2S
Cement B-Slag 8 90 days after SD
Mo
no
carb
o
Me
lili
te
Me
lili
teM
eli
lite
Me
lili
te
Me
lili
te
Me
lili
te Me
lili
te
C2S
Hy
dra
talc
ite
CH
CH
C2S
CHC
2S
CH
CH
C2S
CH
CH
Position [°2 CuKα]
10 20 30 40 50 60
Ca
lcit
e +
C-S
-H
C2S
C2S
C2S
CH
CH
CH
CH
CH
CHC
alc
ite
C2S
C2S
Cement B 90 days
C2S
Ca
lcit
e +
C-S
-H
C2S
Cement B-Slag 8 90 days after SD
Mo
no
carb
o
Me
lili
te
Me
lili
teM
eli
lite
Me
lili
te
Me
lili
te
Me
lili
te Me
lili
te
C2S
Hy
dra
talc
ite
CH
CH
C2S
CHC
2S
CH
CH
C2S
CH
CH
XRD results SEM results
International Summit on Cement Hydration Kinetics
Selective dissolution: conclusion
Not able to dissolve
all cementitious phases
except slag
Selective dissolution
International Summit on Cement Hydration Kinetics
How to measure the reactivity of slag
• Selective dissolution
• Recrystallisation by DSC
• SEM-Image analysis on BSE and
mapping
• Isothermal calorimetry
• Chemical shrinkage
International Summit on Cement Hydration Kinetics
Recrystallisation by DSC: principle
Recrystallise slag at high temperatures (>800°C)
Hypothesis: all amorphous slag recrystallises
Quantify the corresponding peak
Slag 1 Slag 2 Slag 3
MgO 4.7 8.4 8.2
Al2O3 14.6 12.2 11.9
SiO2 33.9 33.6 35.1
CaO 44.5 42.5 42.8
Na2O 0.24 0.26 0.3
S 0.33 1.7 0.37
K2O 0.62 0.45 0.61
TiO2 0.69 0.49 0.59
MnO 0.66 0.55 0.37
FeO <0.1 0.12 0.09
Melilite(C2AS + C2MS2)
Merwinite(C3MS2)
[Regourd, 1980]
International Summit on Cement Hydration Kinetics
296 J/g DH= 0%
Recrystallisation by DSC: results
Results
International Summit on Cement Hydration Kinetics
Recrystallisation by DSC: results
8 J/g DH= 93%
A-S8 7d
unrealistic!
Results
International Summit on Cement Hydration Kinetics
Recrystallisation by DSC: conclusion
DSC
All amorphous slag does not recrystalliseInterference with belite
International Summit on Cement Hydration Kinetics
How to measure the reactivity of slag
• Selective dissolution
• Recrystallisation by DSC
• SEM-Image analysis on BSE and
mapping
• Isothermal calorimetry
• Chemical shrinkage
International Summit on Cement Hydration Kinetics 32
Image analysis of BSE
0 50 100 150 200 250
AN
Slag 8 CH
CSH
For Cements-Slag 1& 8
Slag 8 CH
Overlap between CH and Slag 8 grey levels
Grains of slag as a function of
its chemical composition
Isolate Slag 8 and CH?Similar BS coefficients
Different chemical elements
Degree of hydration
Reactivity of slag-SEM-IA-mapping
Map of Mg
Needs fast detector to be practical
International Summit on Cement Hydration Kinetics 33
0 5 10 15 20 25 30 35 200 400 6008000
10
20
30
40
50
60
70
80
90
100
A-S1
A-S8
Degre
e o
f re
acti
on
of
slag (
%)
T ime (days)
0 5 10 15 20 25 30 35 200 400 6008000
10
20
30
40
50
60
70
80
90
100
Degre
e o
f re
acti
on
of
slag (
%)
T ime (days)
B-S1
B-S8
0 5 10 15 20 25 30 35 200 400 6008000
10
20
30
40
50
60
70
80
90
100
C-S1
C-S8
Degre
e o
f re
acti
on
of
slag (
%)
T ime (days)
For all the Cementitious systems, the slag S8 is always more reactive than slag S1
Reactivity of slag-SEM-IA-mapping
Degree of reaction of slag
International Summit on Cement Hydration Kinetics 34
Outline
SEM (BSE-IA-mapping)
→ gives realistic range with errors which be reduced with
new EDS detector
Isothermal calorimetry
→ gives realistic range
→ needs more investigation on calibration (enthalpy of
slag or external method)
Recrystallisation of slag by DSC
→ problematic due to huge background contribution
How to quantify the degree of reaction slag?
C-S-H composition: indicator of reactivity
International Summit on Cement Hydration Kinetics
How to measure the reactivity of slag
• Selective dissolution
• Recrystallisation by DSC
• SEM-Image analysis on BSE and
mapping
• Isothermal calorimetry
• Chemical shrinkage
International Summit on Cement Hydration Kinetics
Isothermal calorimetry: use of inert filler
Tests on B systems with an inert filler (quartz)as a reference
0 4 8 12 16 20 24 280
100
200
300
400
500
600
700
800
C
um
ula
tiv
e h
eat
(J.g
-1 o
f cem
en
t)
T ime (days)
100% B
60% B-40% Q
Filler effect
International Summit on Cement Hydration Kinetics 37
0 4 8 12 16 20 24 280
100
200
300
400
500
600
Cu
mu
lati
ve h
eat
(J.g
-1 o
f cem
en
t)
T ime (days)
100% B
60% B-40% Q
60% B-40% S1
60% B-40% S8
Filler effect
Contribution of S1 S8
Method: subtract filler effect to blended curve in order to isolate
the contribution of the slag
Reactivity of slag-Isothermal calorimetry
International Summit on Cement Hydration Kinetics 38
Reactivity of slag-Isothermal calorimetry
0 5 10 15 20 25 30 35 400
1
2
3
4
Heat
(W.k
g-1 o
f cem
en
t)
T ime (hours)
100% B
60 % B-40% Q
60 % B-40% S1
60 % B-40% S8
0 4 8 12 16 20 24 280
100
200
300
400
500
600
Cu
mu
lati
ve h
eat
(J.g
-1 o
f cem
en
t)
T ime (days)
100% B
60% B-40% Q
60% B-40% S1
60% B-40% S8
0 4 8 12 16 20 24 280
50
100
150
200
250
300
350
400
Time (days)
Su
btr
ated
cu
mu
lati
ve h
eat
curv
es (
J.g-1
of
cem
ent)
B-S1
B-S8
Early age to treat
with deconvoltion
approach to isolate
the contribution of
different phases
System A
International Summit on Cement Hydration Kinetics 39
Reactivity of slag-Isothermal calorimetry
0 5 10 15 20 25 30 35 400
1
2
3
4
5
6
7
8
Heat
(W.k
g-1 o
f cem
en
t)
T ime (hours)
100% A
60 % A-40% Q
60 % A-40% S1
60 % A-40% S8
70 % A-30% FA1
70 % A-30% FA2
90 % A-10% SF
0 4 8 12 16 20 24 280
100
200
300
400
500
600
Cu
mu
lati
ve h
eat
(J.g
-1 o
f cem
en
t)
T ime (days)
100% A
60% A-40% S1
60% A-40% S8
60% A-40% Q
0 4 8 12 16 20 24 280
50
100
150
200
250
300
350
400
Time (days)
Dif
fere
nce o
f cu
mu
lati
ve h
eat
cu
rves
(J.g
-1 o
f cem
en
t)
A-S1
A-S8
System B
International Summit on Cement Hydration Kinetics 40
Reactivity of slag-Isothermal calorimetry
0 5 10 15 20 25 30 35 400.0
0.5
1.0
1.5
2.0
2.5
3.0
Heat
(W.k
g-1 o
f cem
en
t)
T ime (hours)
0 4 8 12 16 20 24 280
100
200
300
400
500
600
Time (days)
Cu
mu
lati
ve h
eat
(J.g
-1 o
f cem
en
t)
100% C
60% C-40% S1
60% C-40% S8
60% C-40% Q
70 % C-30% FA1
70 % C-30% FA2
70% C-30% Q
90% B-10% SF
0 4 8 12 16 20 24 280
50
100
150
200
250
300
350
400
Time (days)
Su
btr
ate
d c
um
ula
tiv
e h
eat
cu
rves
(J.g
-1 o
f cem
en
t)
C-S1
C-S8
System C
International Summit on Cement Hydration Kinetics 41
Outline
SEM (BSE-IA-mapping)
→ gives realistic range with errors which be reduced with
new EDS detector
Isothermal calorimetry
→ gives realistic range
→ needs more investigation on calibration (enthalpy of
slag or external method)
Recrystallisation of slag by DSC
→ problematic due to huge background contribution
How to quantify the degree of reaction slag?
Combine both to calibrate the calorimetry curves
C-S-H composition: indicator of reactivity
International Summit on Cement Hydration Kinetics 42
Reactivity of slag-Isothermal calorimetry calibrated by SEM
Method to calibrate isothermal calorimetry curves
0 4 8 12 16 20 24 280
50
100
150
200
250
300
Time (days)
Dif
fere
nce o
f cu
mu
lati
ve h
eat
cu
rves
(J.g
-1 o
f cem
en
t)
0
5
10
15
20
25
30
35Slag 1 D
egre
e o
f reactio
n o
f slag
from
SE
M/IA
-map
pin
g (%
)
0 4 8 12 16 20 24 280
50
100
150
200
250
300
350
400
Time (days)
Dif
fere
nce o
f cu
mu
lati
ve h
eat
cu
rves
(J.g
-1 o
f cem
en
t)
0
10
20
30
40
50
60
70
Degre
e o
f reactio
n o
f slag
from
SE
M/IA
-map
pin
g (%
)
Slag 8
International Summit on Cement Hydration Kinetics
Isothermal calorimetry: conclusions
Gives continuous measurements of
realistic degrees of reaction of the slag
Isothermal calorimetry
But several hypotheses!The difference of cumulative curves of filler and slag
is attributed only to the contribution of slag
The heat of solution of slag concerns pure slags and does not correspond to the one activated by alkaline
International Summit on Cement Hydration Kinetics
How to measure the reactivity of slag
• Selective dissolution
• Recrystallisation by DSC
• SEM-Image analysis on BSE and
mapping
• Isothermal calorimetry
• Chemical shrinkage
International Summit on Cement Hydration Kinetics
Isothermal Calorimetry(TAM Air, Thermometric) at a temperature of 20.0 0.1ºC
Ex-situ mixing
8 samples / 60 k$ instrument
Chemical Shrinkage(Dilatometry)
20 samples / 5 k$ instrument
Backscattered electron/Imageanalysis (BSE/IA)
1 sample / 300 k$ instrument
Methodology
International Summit on Cement Hydration Kinetics
Chemical shrinkage-results
0 4 8 12 16 20 24 280.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
Ch
em
ical
shri
nk
age
(mL
/g o
f cem
en
t)
T ime (days)
100% A
60% A-40% S1
60% A-40% S8
0 4 8 12 16 20 24 280.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
Ch
em
ical
shri
nk
age
(mL
/g o
f cem
en
t)
T ime (days)
100% B
60% B-40% S1
60% B-40% S8
0 4 8 12 16 20 24 280.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
Ch
em
ical
shri
nk
age
(mL
/g o
f cem
en
t)
T ime (days)
100% C
60% C-40% S1
60% C-40% S8
S1>S8 S1<S8
S1<S8 Discrimination between 2 slags but needs to be corrected by filler effectFind a method of calibration to link the curve to degree of reaction of slag
International Summit on Cement Hydration Kinetics
Conclusions: How to measure the reactivity of slag?
Selective dissolution does not work
DSC does not recrystallise completely the slag
Combine both to calibrate the calorimetry curves
SEM (BSE-IA-mapping) gives realisticrange but large errors which will berefined
Isothermal calorimetry gives realisticrange but needs more investigation oncalibration
Chemical shrinkage give continuousmeasurements but needs to becalibrated with an external method
In progress, check on calorimetry
International Summit on Cement Hydration Kinetics
Summary
SCMs similar in size to cement effect of silicate is
mostly dilution
Effect on alumino sulfate reactions dramatic and
not completely explained
Very fine fillers, e.g. Silica fume indicate
enhanced nucleation effect
To study kinetics of SCM, challenge is
measurement
Calorimetry and chemical shrinkage look promising as continuous methods, questions of calibration
48
International Summit on Cement Hydration Kinetics
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