Monomer impregnation of hardened cement paste (HCP)

CEMENT and CONCRETE RESEARCH. Vol. 2, pp. 481-485, 1972. Pergamon Press, Inc. Printed in the United States.

NOTES MONOMER

IMPREGNATION

OF HARDENED

CEMENT

PASTE

(HCP)

Eigil V. SCrensen and Fariborz Radjy Building Materials Laboratory Technical University of Denmark 2800 Lyngby, Denmark

The production involves men;

three

stages:

2) impregnation

lymerization

sequence;

we describe

(equivalent to cement

length.

tubes

This

curing

with respect

to the

second

molds

cured

produces

to thermal

(MMA);

3) po-

of an

Cement

paste with water in vacuum,

diameter (97°C,

and

by 60mm

latm.)

after the first

HCP specimens

for 12

5-6 hours).

that are essentially

a structure

treatment

used were

methacrylate

Portland

of cement

in steam

were removed

speci-

of HCP.

of 0.45 and 0.50 were mixed

were

(I)

stage of this production

Standard

as well as having

The monomers

Concrete

with monomer;

impregnation

Two batches

composites

is a summary

of 16 to 18mm internal

procedure

fully hydrated,

methyl

i).

The specimens

(the glass

This note

the monomer

(w/c) ratios

days

specimen

used was a Danish

to ASTM

in glass

of the hardened

of the dried

(2) relating

The cement

concrete-polymer

I) drying

of the monomer.

investigation

cast

of preformed

which

is stable

(3).

commercially

available

the MMA monomer

styrene

contained

and

3% benzoyl

peroxide. We studied ders,

the impregnation

and powdered

specimens

were dried by bringing sure of 2.3 torr

(149-250

for both as-cast

microns).

them to equilibrium

in an evacuated

97°C; the drying was terminated reached

process

img.g.-l(day) -I.

glass

The cylinders

at a water

apparatus

vapor pres-

thermostated

when the rate of weight

Current

481

work at this

cylin-

at

loss

laboratory

shows

482

Vol. 2, No. 4 NOTES

FIG. I Apparatus for liquid phase impregnation

]alibrated graduated tube

lil

Stopcock B

/Greased

ground joint

that this drying procedure D-drying method

is approximately

(4) at 25°C.

The powdered

equivalent to the specimens were

D-dried according to the standard procedure. The cylinders were subjected to both gas phase and liquid phase impregnation,

while the powdered specimens were impreg-

nated from the gas phase only. placed in vacuum desiccators

The powdered

specimens were

(at 25°C) containing the appropri-

ate monomer liquid or distilled water; the amount of monomer or water adsorption was determined by periodic weighing of the specimens.

Of the cylinders,

was impregnated with gaseous

only one

styrene at 25°C.

placed in an evacuated apparatus, lary tube

(2mm diameter)

(w/c=0.45, diameter=16mm) This specimen was

containing a calibrated

capil-

filled with styrene; the amount of ad-

sorption as a function of time was obtained by noting the position of the meniscus

in the capillary tube.

Four specimens were impreg-

nated from the liquid phase by using the apparatus A predried

shown in Fig.

specimen was placed in the apparatus and, after

i.

Vol. 2, No. 4

483 NOTES TABLE

i

M a x i m u m Monomer

Specimen nr Cylinder (liquid phase)

Styrene 3 cm pr.100 g dry HCP

W/C

2F

MMA

Water 3 cm pr.100 g dry HCP

3

cm pr.100 ~ dry HCP

18.3

4D

0.45

20.1

Powder (vapor phase)

16.4

3F

Cylinder (liquid phase)

Adsorption

x) -+ 1.7

18.6 + 1.5

25.0

+- 0.2

20.3

3C

0.50

24.2

Powder (vapor phase

x) 30.6~2.2

Molecular size

(A 2 ) + - one standard

x) Mean

evacuating through tored

35".5

the specimen

the stopcock

The results Table and

tube,

B.

degassed

The progress

monomer

was

introduced

of impregnation

of the meniscus

was moni-

in the graduated

of time.

are presented

1 shows the maximum

3 illustrate

10.5

deviation.

by noting the position

tube as a function

34.6

the rates

in Table

amounts

i, and Figs.

of impregnation,

of impregnation

2 and

while

3.

Figs.

2

for the cylindrical

specimens. The maximum styrene, vations size

amount

MMA and water (5), there

of impregnation (Table

is a qualitative

(in A 2, based on liquid

of impregnation. w/c=0.45 inders

i).

show that the maximum

from the liquid

ing gas phase

phase

impregnation

In keeping

between

and the maximum

the results amount

in the order:

with other obser-

correlation

densities)

Furthermore,

increases

molecular amount

for the batch with

of impregnation

for the cyl-

is about the same as the correspond-

for the powders.

484

Vol. 2, No. 4 NOTES

0.1;

I

I

I

I

I

I II

I

1

1

I

I

I

I I I I

1

I

I

I

I

I I I

J

L I I 1

-oic 13.. U I"

./

.~008

0.06

o.
_~ o.o~ ~,0.02

®

e-~'~-'e--q'el®-T

O.OC

I I I I I 101

I

I

1

/

1 I I I I I

1

I

1o3

10 2

Time (hours)

FIG. 2 Adsorption of Styrene from the vapor phase (no.iC) The most remarkable of our results

is the extremely

rapid rate of liquid tion

capillary

the main driving I

i

Iii

I

I

i

i

i

I

[111

ison of Figs.

[

gas phase 022

j'

Z ~02C

impregna-

for the cylinders

probably,

(Fig.

suction

force.

3); is

Compar-

2 and 3 shows that

impregnation

ently three

feature

orders

is appar-

of magnitude

slower than liquid

phase

impreg-

nation.

based on

~0~8

/o °/

Actually,

~o16 (Jl&

//

£

I

i • io,ol ..~

available

I

k_

ter, we expected

. . . . . . .

o12

rates Fig. 1°1

Time Imms]

107

FIG. 3 Adsorption of monomers from the liquid phase

approaching 2.

adsorbate? quite high.

However,

of between

and liq-

uid phase

impregnation

has per-

plexed

us for some time.

the mechanism

Could

of diffusion

when the specimen

liquid

be so is

phase of the same

work at this laboratory

from a vapor phase

when the vapor

those

of gas phase

Continuing

shows that the rate of adsorption

impregnation

the rates

with the gas, rather than the We think not.

data for wa-

The discrepancy

different in contact

diffusion

is provided

is, in fact,

by a liquid

Vol. 2, No. 4

485 NOTES

source, the rate of evaporation

from the source and flow through

the apparatus tubing may be slower than diffusion sorbent.

Under these circumstances,

then, the adsorption rates

observed will be more a characteristic specimen.

Furthermore,

similar slowing effect.

leakage

into the ad-

of the apparatus than the

in a vacuum system will have a

Thus, we think it probable that a combi-

nation of the above problems resulted in the slow adsorption results of Fig.

2.

For comparison purposes, we also tried to impregnate the dried cylinders with water. fractured specimen miscellaneous work with:

some of

All such attempts resulted

(two halves, across a diameter).

in a

As another

remark, we found that MMA is quite difficult to

it swells rubbers

(viton), and it dissolves

both

apiezon and silicone greases. Our observations

demonstrate

that liquid phase impregnation

of the MMA and styrene monomers, without applying pressures higher than one atm., are very rapid.

We feel that gas phase impreg-

nation should be as rapid; this expectation,

however,

is not born

out by our observations. This note is based on one of the authors' thesis

(i), which was partially

Videnskabelige

(E.V.S.) M.S.

supported by Statens Teknisk-

Pond 2056.B-163K-143.

This support

is most

gratefully acknowledged. References (i)

Steinberg, M. et al., Concrete-Polymer Materials, of Commerce, BNL 50134 (1968).

(2)

S~rensen, E. V., Monomer-Imprmgnering of Hmrdnet Portland Cement Pasta, Building Materials Laboratory, Technical University of Denmark, Technical Report no. 18, Copenhagen (1970).

(3)

Sellevold, E. J., Anelastic Behavior of Hardened Portland Cement Paste, Stanford University, Technical Report no. 113, Stanford (1969).

(4)

Copeland, L. E. and Hayes, J. C., Research Department Bulletin no. 47, Portland Cement Association, Chicago (1953).

(5)

Mikhail, R. S. and Selim, S. A., Highway Research Board, Special Report no. 90, Washington, D. C., 123 (1968).

US Dept.