the nanostructure of calcium-silicate-hydrate: the role of interlayer water
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ACI Spring 2008 Convention Sub-Committee 236D meeting. The nanostructure of Calcium-Silicate-Hydrate: The role of interlayer water Rouhollah Alizadeh, James J. Beaudoin, Laila Raki Institute for Research in Construction, National Research Council Canada. Outline. Introduction - PowerPoint PPT PresentationTRANSCRIPT
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The nanostructure of
Calcium-Silicate-Hydrate: The role of interlayer water
Rouhollah Alizadeh, James J. Beaudoin, Laila RakiInstitute for Research in Construction, National Research Council Canada
ACI Spring 2008 ConventionSub-Committee 236D meeting
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Outline
Introduction
Calcium-Silicate-Hydrate (C-S-H)
Models
Experiments and Results
Sample PreparationHelium InflowX-Ray Diffraction29Si NMRAnalogies with hydrated cement
Concluding Remarks
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Calcium
Hydroxide
Calcium-Silicate-Hydrate (C-S-H), 60% of the paste
Ettringite
C-S-Hin Cement Paste
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C-S-HStructural Models
Jennings CM-II model, 2008
Feldman-Sereda model, 1968Powers-Brunauer model, 1946
Dreierkette-based models, T/J model by Taylor 1986
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Experiments Synthesis of Phase Pure C-S-H
1.2 CaO + SiO2 + H2O C-S-H
The C-S-H samples were conditioned at 11%RH
Samples were dried by applying vacuum and heat
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He, 2 atm
Experiments Helium Inflow
Helium Pycnometer
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Helium inflow versus time at each weight loss for C-S-H
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 10 20 30 40 50
TIME, HOURS
HE
LIU
M IN
FL
OW
, mL
/10
0g
.
0.00 0.48
2.56 4.12
4.88 5.08
6.16 6.73
7.68 7.84
Weight Loss from 11%RH (%)
Experiments Helium Inflow
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0.20
0.40
0.60
0.80
1.00
1.20
1.40
0 1 2 3 4 5 6 7 8 9 10
Weight Loss From 11%RH, %
He
lium
Inflo
w, m
L/1
00
g .
Total helium inflow versus weight loss for C-S-H
Increase in the helium inflow for up to about 5% weight loss
Decrease in the helium inflow when more water is removed
Experiments Helium Inflow
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ExperimentsX-Ray Diffraction
0
100
200
300
400
500
600
700
5 6 7 8 9 10 11 12
2q, Degree
Inte
nsi
ty, A
rbitr
ary
Un
its1.18 nm
0.96 nm
X-ray diffraction patterns for C-S-H showing changes in 002 basal spacing
Weight Loss, %
0 %
5 %
10 %
1.07 nm
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Change in the basal spacing versus weight loss
0.95
1.00
1.05
1.10
1.15
1.20
0 2 4 6 8 10 12
Weight Loss, %
002
basa
l-spa
cing
, nm
Sudden decrease in the basal spacing between 4 and 6 % weight loss
Total decrease of 0.22 nm in basal spacing which is close to the diameter of a water molecule (0.28 nm)
ExperimentsX-Ray Diffraction
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0.95
1.00
1.05
1.10
1.15
1.20
0 2 4 6 8 10 12
Weight Loss, %
002
basa
l-spa
cing
, nm
0.2
0.4
0.6
0.8
1
1.2
1.4
Hel
ium
Inflo
w, m
L/10
0g
002 basal-spacing
Helium Inflow
ExperimentsHelium Inflow and XRD
XXXXXXXXX
XXXXXXXX
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Experiments29Si NMR
-110-100-90-80-70-60
0.0
3.7
6.3
Weight Loss from 11%RH (%)
11.6
Chemical Shift (from TMOS), ppm
0.3
0.35
0.4
0.45
0.5
0.55
0.0 2.0 4.0 6.0 8.0 10.0 12.0
Weight Loss, %
Q2/
Q1
Change in the polymerization of C-S-H on drying
Q1 Q2
Q1
Q2
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X XX X X
Schematic nanostructural model of C-S-H
Experiments29Si NMR
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Condensation of silicate chains in the interlayer
Increased shielding of Q1 sites
Formation of new Q2 silicon sites
No sign of Q3 was observed in the spectrum
Experiments29Si NMR
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ExperimentsAnalogies with hydrated cement paste
Total helium inflow versus weight loss for hydrated Portland cement
Feldman, 1970s
Polymerization of C-S-H and hydrated -C2S, effect of heat treatment
Cong & Kirkpatrick, 1995
Q1 Q2
C-S-H (C/S: 1.2)
Cement Paste (W/C: 0.4)
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Synthetic C-S-H can be used as a viable prototype for C-S-H present in hydrated Portland cement.
Significant decrease in the interlayer spacing occurs at about 4-6% weight loss which corresponds well with the decrease in the helium inflow and increase in the silicate
polymerization.
Helium inflow in hydrated cement paste follows a similar pattern to that of synthetic C-S-H. Increased silicate polymerization of hydrated cement paste has been observed on drying.
Conclusions
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• Alizadeh R., Beaudoin J. J., and Raki L. “C–S–H (I)—A Nanostructural Model for the Removal of Water from Hydrated Cement Paste?” J. Am. Ceram. Soc. 90 (2) 670-672 (2007)
The new results will be published soon.
Reference
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Acknowledgments
NRC-IRC
Dr. Steven LangDr. Tai SatoMr. Gordon ChanMr. Jim Margeson
Thank you