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
Outline
Introduction
Calcium-Silicate-Hydrate (C-S-H)
Models
Experiments and Results
Sample PreparationHelium InflowX-Ray Diffraction29Si NMRAnalogies with hydrated cement
Concluding Remarks
Calcium
Hydroxide
Calcium-Silicate-Hydrate (C-S-H), 60% of the paste
Ettringite
C-S-Hin Cement Paste
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
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
He, 2 atm
Experiments Helium Inflow
Helium Pycnometer
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
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
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
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
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
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
X XX X X
Schematic nanostructural model of C-S-H
Experiments29Si NMR
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
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)
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
• 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
Acknowledgments
NRC-IRC
Dr. Steven LangDr. Tai SatoMr. Gordon ChanMr. Jim Margeson
Thank you
