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Interlayer desorption of CSH(1)
CEMENT and CONCRETERESEARCH. Vol. 2, pp. 643-646, 1972. Pergamon Press, Inc Printed in the United States.
INTERLAYER DESORPTIONOF CSH(1)
R.H. Smith and P. Bayliss Department of Geology, University of Calgary, Alberta
(Communicated by L. E. Copeland)
ABSTRACT: X-ray d i f f r a c t i o n of CSH(1) with a calcium to silicon ratio of 1.07 after room temperature desorption showed three d i s t i n # t basal spacing ranges, 13.3-12.1, 10.810.2 and 9.7A. Examination of a saturated sample after 25 months compared to 12 months showed a significant basal spacing increase had occurred with aging. Partial monolayer desorption begins immediately the vapour pressure drops below saturation. Complete water monolayer desorption begins at 42-35% relative humidity.
R~ntgenstrahlung von CSH(1) mit einem Ca:Si Verh~Itnis von 1.07 nach Desorption in Raumtemperatur zeigte drei bestimmte Werte ba~aler Gitterabst~nde, 13.3-12.1, 10.8-10.2, und 9.7A. Untersuchung einer ges~ttigten Probe nach 25 Monaten, im Vergleich zu 12 Monaten, ergab eine bedeutende Erh6hung der basalen Gitterabst~nde mit dem Alter der Probe. Teilweise Einzelschicht Desorption beginnt sofort als der Dampfdruck unter den S~ttigungswert f ~ l l t . Vollst~ndige Einzelschicht Desorption des Wassers fangt an bei 42-35% r e l a t i v e r Feuchtigkeit.
643
644
Vol. 2, No. 6 INTERLAYER, DESORPTION, CSH(1), AGING Introduction A previous paper (I) indicated a large change in basal spacing for CSH(1)
from the saturated condition to D-dried as measured by X-ray diffraction.
It
therefore appears worthwhile to investigate the intermediate stages of hydration as the drying conditions at which these stages are produced may yield insights into the engineering behavior of concrete. Methods The CSH(1) sample with a calcium to silicon ratio of 1.07 was prepared as described previously (1).
I t was 25 months old at the commencement of
the desorption experiments. Twelve individual specimens from this sample were equilibrated at room temperature in desicators to weight equilibrium over saturated aqueous salt solutions or dehydration agents. Vapour pressures over the three saturated aqueous salt solutions used, as measured by a hygrometer, are given in Table I.
In addition, Table l presents vapour pressures
for the dehydration agents as reported in the literature (2, 3, and 4).
No
attempt was made to measure these values. The saturated specimen was taken directly from the i n i t i a l saturated state for testing. An X-ray diffractometer as described previously (1) was used. Each specimen was composed of sufficient material to f i l l
four X-ray slides.
The material in the X-ray slide was returned to the specimen and thoroughly remixed after an X-ray diffraction pattern
was taken. Then another X-ray
slide was f i l l e d from the specimen. Ten powder X-ray diffraction patterns from 4.5 to lO.O° 2Q were taken from each of the thirteen specimens. The basal spacings recorded by the ten patterns from each specimen were averaged to obtain a representative basal spacing produced by each vapour pressure. Results and Discussion The average basal spacings exhibited by the CSH(1) specimens listed in Table l are graphed in Figure I.
The basal spacing of saturated CSH(1)
after 12 months has been reported previously (1) to be 12.5 ~.
This CSH(1)
then remained in suspension without agitation for an additional 13 months during which the basal spacing increased to 13.3 2. In addition, the peak to background ratio increased from 2.0:I to 2.3:1.
Apparently additional
water molecules entered between the layered silicate sheets, which improved the crystallinity and increased the basal spacing. A basal spacing increase with age has not been generally recognized. A single basal spacing in CSH(1) decreases from 13.3 to 13.0 ~ near saturation.
Thus interlayer water may be
Vol. 2, No. 6
645
INTERLAYER, DESORPTION,CSH(1), AGING TABLE 1 The Basal Spacing (~) of CSH(1) with Si/Ca Ratio of 1.07 at Various Water Vapour Pressures with Corresponding Solution or Dehydration Agent Basal-spacing
Water Vapour Pressure mmHg
Solution or Dehydration Agent
13.3(I) 13.0(1)
760 320
H20 KOH soln
13.0(I) lO.8(1) 12.9(I) lO.7(1) 12.5(I) lO.3(1) 12.1(1) 12.1(1) 12.3(I) I0.2(I) 9.7(I) 9.7( l ) 9.7(I ) 9.7(I )
265 175 2.8 0.8 0.34 0.18 0.03 0.014 O.005 O.O001 approx. O.O00001 approx.
K2C2H302 soln LiCI2.H20 soln CuSO4 anhydrous NaOH fused CaCl2 fused CaBr2 fused SiO2 gel KOH fused Al 203 Mg(Cl04) 2 P205
i 13.
O
o~
O
12-
O
Z
0,. ..J
II-
__J
O~
I00
AGE =25
9- -----~, 10-6
I i0 ~,e
,~-~ WATER
,,~-~ VAPOR
,oPRESSURE,
MONTHS
',
,,
,,~
mm. Hg.
FIG. 1 The basal spacing (2) of CSH(1) with Si/Ca ratio of 1.07 at various water vapour pressures.
646
Vol. 2, No. 6 INTERLAYER, DESORPTION, CSH(1), AGING
partially withdrawn at high relative humidities.
Therefore insofaras the
desorption behaviour of this CSH(1) reflects that of cement, interlayer water movement may play a role in creep and shrinkage of concrete. Desorption at 265, 175 and 2.8 mmHg produced two different hydrated phases with basal spacings at 13.0-12.5 R and I0.8-I0.3 ~.
The ratio of the
13.0-12.5 ~ to the I0.8-I0.3 ~ peak height decreases from l.O at 265 mmHg to 0.65 at 175 mm Hg, and finally to 0.59 at 2.8 mm Hg.
The stability region of
these two hydrated phases ranged from 320-265 mmHg to 2.8-0.8 mm Hg.
The
decrease in the water vapour pressure caused the expected conversion of the more hydrated phase (13.0-12.5 ~) to the less hydrated phase (I0.8-I0.3 ~). Desorption at 0.8, 0.34 and 0.18 mm Hg produced only a single basal spacing at 12.3-12.1 ~.
This basal spacing was unexpected because either
a I0.3 ~ reflection with a small 12.5 ~ reflection as at 2.8 mm Hg or a I0.3-10.2 ~ reflection as at 0.03 mm Hg seemed likely as indicated by the dashed extensions of the hydrated phases in Figure I.
The 12.3-12.1 ~ basal
spacing is not a 002 reflection from a regular mixed layer as a careful search revealed no 24 R reflection.
The half height reflection width is
significantly greater than the single refiections either at 13.3-13.0 ~ or at 9.7 X. dition.
Thus the 12.3-12.1 ~ reflection appears to be a metastable conFrom the I0.2 ~ basal spacing at 0.03 mmHg, there is a distinct
reduction of the basal spacing to 9.7 ~ at lower water vapour pressures. Acknowledgements Financial assistance is acknowledged from an N.R.C. of Canada grant. References I.
R.H. Smith, P. Bayliss, B.R. Gamble and R.H. Mills, Cem. Concr. Res. _2, p. 000 (1972).
2.
Handbookof Chemistry and Physics, P.E.-28, Chemical Rubber Co., N.Y. (Ig70-71).
3.
Handbookof Analytical Chemistry, P. 3-28, McGraw-Hill, N.Y. (1963).
4.
S. Brunauer and S.A. Greenberg, Fourth Int. Symp. Chem. Cement, p. 135, N.B.S. Monograph 43, Washington (1960).
INTERLAYER DESORPTIONOF CSH(1)
R.H. Smith and P. Bayliss Department of Geology, University of Calgary, Alberta
(Communicated by L. E. Copeland)
ABSTRACT: X-ray d i f f r a c t i o n of CSH(1) with a calcium to silicon ratio of 1.07 after room temperature desorption showed three d i s t i n # t basal spacing ranges, 13.3-12.1, 10.810.2 and 9.7A. Examination of a saturated sample after 25 months compared to 12 months showed a significant basal spacing increase had occurred with aging. Partial monolayer desorption begins immediately the vapour pressure drops below saturation. Complete water monolayer desorption begins at 42-35% relative humidity.
R~ntgenstrahlung von CSH(1) mit einem Ca:Si Verh~Itnis von 1.07 nach Desorption in Raumtemperatur zeigte drei bestimmte Werte ba~aler Gitterabst~nde, 13.3-12.1, 10.8-10.2, und 9.7A. Untersuchung einer ges~ttigten Probe nach 25 Monaten, im Vergleich zu 12 Monaten, ergab eine bedeutende Erh6hung der basalen Gitterabst~nde mit dem Alter der Probe. Teilweise Einzelschicht Desorption beginnt sofort als der Dampfdruck unter den S~ttigungswert f ~ l l t . Vollst~ndige Einzelschicht Desorption des Wassers fangt an bei 42-35% r e l a t i v e r Feuchtigkeit.
643
644
Vol. 2, No. 6 INTERLAYER, DESORPTION, CSH(1), AGING Introduction A previous paper (I) indicated a large change in basal spacing for CSH(1)
from the saturated condition to D-dried as measured by X-ray diffraction.
It
therefore appears worthwhile to investigate the intermediate stages of hydration as the drying conditions at which these stages are produced may yield insights into the engineering behavior of concrete. Methods The CSH(1) sample with a calcium to silicon ratio of 1.07 was prepared as described previously (1).
I t was 25 months old at the commencement of
the desorption experiments. Twelve individual specimens from this sample were equilibrated at room temperature in desicators to weight equilibrium over saturated aqueous salt solutions or dehydration agents. Vapour pressures over the three saturated aqueous salt solutions used, as measured by a hygrometer, are given in Table I.
In addition, Table l presents vapour pressures
for the dehydration agents as reported in the literature (2, 3, and 4).
No
attempt was made to measure these values. The saturated specimen was taken directly from the i n i t i a l saturated state for testing. An X-ray diffractometer as described previously (1) was used. Each specimen was composed of sufficient material to f i l l
four X-ray slides.
The material in the X-ray slide was returned to the specimen and thoroughly remixed after an X-ray diffraction pattern
was taken. Then another X-ray
slide was f i l l e d from the specimen. Ten powder X-ray diffraction patterns from 4.5 to lO.O° 2Q were taken from each of the thirteen specimens. The basal spacings recorded by the ten patterns from each specimen were averaged to obtain a representative basal spacing produced by each vapour pressure. Results and Discussion The average basal spacings exhibited by the CSH(1) specimens listed in Table l are graphed in Figure I.
The basal spacing of saturated CSH(1)
after 12 months has been reported previously (1) to be 12.5 ~.
This CSH(1)
then remained in suspension without agitation for an additional 13 months during which the basal spacing increased to 13.3 2. In addition, the peak to background ratio increased from 2.0:I to 2.3:1.
Apparently additional
water molecules entered between the layered silicate sheets, which improved the crystallinity and increased the basal spacing. A basal spacing increase with age has not been generally recognized. A single basal spacing in CSH(1) decreases from 13.3 to 13.0 ~ near saturation.
Thus interlayer water may be
Vol. 2, No. 6
645
INTERLAYER, DESORPTION,CSH(1), AGING TABLE 1 The Basal Spacing (~) of CSH(1) with Si/Ca Ratio of 1.07 at Various Water Vapour Pressures with Corresponding Solution or Dehydration Agent Basal-spacing
Water Vapour Pressure mmHg
Solution or Dehydration Agent
13.3(I) 13.0(1)
760 320
H20 KOH soln
13.0(I) lO.8(1) 12.9(I) lO.7(1) 12.5(I) lO.3(1) 12.1(1) 12.1(1) 12.3(I) I0.2(I) 9.7(I) 9.7( l ) 9.7(I ) 9.7(I )
265 175 2.8 0.8 0.34 0.18 0.03 0.014 O.005 O.O001 approx. O.O00001 approx.
K2C2H302 soln LiCI2.H20 soln CuSO4 anhydrous NaOH fused CaCl2 fused CaBr2 fused SiO2 gel KOH fused Al 203 Mg(Cl04) 2 P205
i 13.
O
o~
O
12-
O
Z
0,. ..J
II-
__J
O~
I00
AGE =25
9- -----~, 10-6
I i0 ~,e
,~-~ WATER
,,~-~ VAPOR
,oPRESSURE,
MONTHS
',
,,
,,~
mm. Hg.
FIG. 1 The basal spacing (2) of CSH(1) with Si/Ca ratio of 1.07 at various water vapour pressures.
646
Vol. 2, No. 6 INTERLAYER, DESORPTION, CSH(1), AGING
partially withdrawn at high relative humidities.
Therefore insofaras the
desorption behaviour of this CSH(1) reflects that of cement, interlayer water movement may play a role in creep and shrinkage of concrete. Desorption at 265, 175 and 2.8 mmHg produced two different hydrated phases with basal spacings at 13.0-12.5 R and I0.8-I0.3 ~.
The ratio of the
13.0-12.5 ~ to the I0.8-I0.3 ~ peak height decreases from l.O at 265 mmHg to 0.65 at 175 mm Hg, and finally to 0.59 at 2.8 mm Hg.
The stability region of
these two hydrated phases ranged from 320-265 mmHg to 2.8-0.8 mm Hg.
The
decrease in the water vapour pressure caused the expected conversion of the more hydrated phase (13.0-12.5 ~) to the less hydrated phase (I0.8-I0.3 ~). Desorption at 0.8, 0.34 and 0.18 mm Hg produced only a single basal spacing at 12.3-12.1 ~.
This basal spacing was unexpected because either
a I0.3 ~ reflection with a small 12.5 ~ reflection as at 2.8 mm Hg or a I0.3-10.2 ~ reflection as at 0.03 mm Hg seemed likely as indicated by the dashed extensions of the hydrated phases in Figure I.
The 12.3-12.1 ~ basal
spacing is not a 002 reflection from a regular mixed layer as a careful search revealed no 24 R reflection.
The half height reflection width is
significantly greater than the single refiections either at 13.3-13.0 ~ or at 9.7 X. dition.
Thus the 12.3-12.1 ~ reflection appears to be a metastable conFrom the I0.2 ~ basal spacing at 0.03 mmHg, there is a distinct
reduction of the basal spacing to 9.7 ~ at lower water vapour pressures. Acknowledgements Financial assistance is acknowledged from an N.R.C. of Canada grant. References I.
R.H. Smith, P. Bayliss, B.R. Gamble and R.H. Mills, Cem. Concr. Res. _2, p. 000 (1972).
2.
Handbookof Chemistry and Physics, P.E.-28, Chemical Rubber Co., N.Y. (Ig70-71).
3.
Handbookof Analytical Chemistry, P. 3-28, McGraw-Hill, N.Y. (1963).
4.
S. Brunauer and S.A. Greenberg, Fourth Int. Symp. Chem. Cement, p. 135, N.B.S. Monograph 43, Washington (1960).