Further interlayer desorption studies of CSH(1)

CEMENT and CONCRETERESEARCH. Vol. 3, pp. 185-188, 1973. Pergamon Press, Inc

FURTHER INTERLAYER DESORPTION STUDIES OF CSH(])

P. Bayliss Department of Geology University of Calgary, Alberta, Canada

(Communicated by L. E. Copeland)

ABSTRACT X-ray diffraction of CSH(I) samples with a calcium to silicon ratio of ].25 and ].50 after room temperature desorption showed a step-like decrease from ]2.51 to ]O.OA and ]2.4A to 9.9A respectively.

The step-like de-

crease is not as well defined in CSH(I) with a higher calcium to silicon ratio.

A distinct O.6A basal spacing

decrease occurs as the relative humidity drops from ]O0 to 35 percent. R~ngtenstrahlen Beugung von CSH(I) Proben mit einem Ca:Si Verh~ltnis von ].25 und 1.50 zeigte nach Raumtemperatur Desorption eine stufenartige Verminderung von ]2.5A auf IO.OA, bzw. von ]2.4A auf 9.9A.

Bei CSH(1) mit elnem

hOheren Ca:Si Verh~ltnis ist diese stufenartige Verminderung nicht so gut definlert.

Eine ausgepr~gte Verminderung des

basalen Gltterabstrandes von O.6A erfolgt als die relative Feuchtigkeit yon I00~ auf 55~ f ~ l l t .

185

186

Vol. 3, No. 2 INTERLAYER, DESORPTION, CSH(1), AGING

Introduction In an earlier paper

(1), a CSH(I

with a calcium to silicon ratio

of 1.07 was desorped at various water vapour pressures, and its resultant basal spacing was measured by powder X-ray diffraction. a step-like basal spacing decrease with desorption. decided to investigate more CSH(1) samples.

There was

Therefore

it was

First a calcium to silicon

ratio of 1.25 was selected, because it has a ratio intermediate between tobermorite and tobermorite gel.

Secondly a calcium to silicon ratio

of 1.50 was selected, because it has a ratio equal to tobermorite gel. Since CSH(I)

is similar to tobermorite gel, further knowledge of CSH(1)

may indicate the behaviour pattern of tobermorite gel and concrete. Methods The two CSH(1) samples with a calcium to silicon of 1.25 and 1.50 were prepared as described previously

(2). They were 12 months old

when the present desorption experiments commenced.

Twelve individual

specimens from each of these two different samples were equilibrated at room temperature as described previously

(1). The saturated

specimen was taken directly from the initial saturated state for measurement.

The basal spacing was measured by powder X-ray diffrac-

tion as described previously

(I, 2), except that only five patterns

were recorded from each specimen instead of ten. Results and Discussion The average basal spacings exhibited by both listed in Table l are graphed in Figure I. desorption,

CSH(1) specimens

After room temperature

the CSH(1) with a calcium to silicon ratio of 1.25

decreased from 12.5 A to 10.O ~, whereas the CSH(1) with a calcium to silicon ratio of 1.50 decreased from 12.4 A to 9.9 A.

The small

particle size is shown by the large angular width at half peak height of the basal spacing, which ranges from 0.9 ° to 1.9 ° 2e. degree of crystallinity

The low

is shown by the small peak to background ratio

which ranges from 0.2 to l.O. The basal spacings of the 12 months old saturated CSH(1) specimens with calcium to silicon ratics respectively.

of 1.25 and 1.50 are 1205 A and 12.4

These values are similar to that of 12.5 A for CSH(1)

with a calcium to silicon ratio of 1.07, which was examined under

Vol. 3, No. 2

187 INTERLAYER, DESORPTION, CSH(1), AGING

TABLE 1 The Basal Spacings (R) of CSH(1) with Ca:Si Ratio of 1.25 and 1.50 at Various Water Vapour Pressures with Corresponding Solution or Dehydration Agent.

Basal Spacing (~) Ca:Si = 1.25

Water Vapour Pressure

Solution or

mm Hg

Dehydration Agent

Ca:Si = 1.50

12.5(1) 12.3(1)

12.4(1) 12.1(1)

21 8.8

H20 KOH soln.

11.9(1) 11.9(1) 11.7(1) 11.5(1) 11.4(I) I0.9(I) 10.9(I) I0.4(I)

11.7(1) 11.6(1) 11.3(1) 10.8(1) 10.5(I) I0.5(I) 10.5(I) 10.3(I)

7.3 4.8 2.8 0.8 0.34 0.18 0.03 0.014

KC2H302 soln. LiCl.H20 soln. CuSO4 anhydrous NaOH fused CaCl 2 fused CaBr 2 fused SiO 2 gel KOH fused

10.3(1) 10.2(I) lO.O(1)

10.1(!) I0. I(I) 9.9(I)

0.005 0.0001 approx. 0.000001 approx.

A1203 M9(CI04) 2 P205

130 C o : S i = !"25 & C o : S i = 1"50

o~

12-

0

z ///~

~J o. 11f

A

i10AGE : 12 M O N T H S 9

,~-6

1'o-s

1~-'

,b-3 WATER

Ib-2

I'o-'

VAPOUR

PRESSURE

I

,'o

i'0 2

mm. Hg.

Figure 1 The basal spacing (~) of CSH(1) with Ca:Si ratio of 1.25 and 1.50 at various water vapour pressures.

188

Vol. 3, No. 2 INTERLAYER, DESORPTION, CSH(1), AGING

similar conditions as reported previously

(2).

Since the basal

spacing of CSH(1) with a calcium to silicon ratio of 1.07 increased from 12.5 A to 13.3 A with aging from 12 to 25 months

(1), the basal

spacings of the CSH(1) specimens with calcium to silicon ratios of 1.25 and 1.50 will be measured duces an increase

in another year to determine

if aging pro-

in the basal spacing at saturation.

Immediately below saturation,

there was a 0.6 A basal spacing

decrease as the relative humidity dropped from lO0 to 35 percent. This

indicates a partial withdrawal

of interlayer water.

insofaras the desorption behaviour of these CSH(1) tobermorite gel,

Therefore

reflect that of

interlayer water movement may effect creep and shrink-

age of concrete. Both curves

in Figure l indicate a step-like reduction

spacing with desorption. to be released

in basal

This shows that the interlayer water tends

in discrete units, although not nearly as discrete as

those from CSH(I) with a calcium to silicon ratio of 1.07 as reported previously

(I).

Therefore as the calcium to silicon ratio of CSH(I)

increases from 1.07 to 1.25 and then to 1.50, there is a progressive decrease water

in the regularity between the calcium silicate sheets and the

layer sheets. Afknowled~ements Drs. R.H. Smith and H. Wieser are thanked for helpful discussions.

Financial

assistance

is acknowledged

from an N.R.C. of Canada grant.

References I.

R. H. Smith and P. Bayliss, Cem. Concr.

2.

R. H. Smith, P. Bayliss,

Res. ~, p. 559 (1972).

Res. ~, p. 643

(1972).

B. R. Gamble and R.H. Mills, Cem. Concr.