United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-96/004 August 1996
EPA Project Summary
Freeze-Thaw Cycling and Cold
Temperature Effects on
Geomembrane Sheets and
Seams
A. I. Comer, M.L. Sculli, and Y. G. Hsuan
The effects of freeze-thaw cycling on
the tensile strength of 19 geomembranes
and 31 different seam types were inves-
tigated. The study was performed in
three parts using different test condi-
tions. Part I involved incubating uncon-
fined specimens in freeze-thaw cycles
and then performing tests at room tem-
perature. Part II involved incubating un-
confined specimens in freeze-thaw
cycles and then performing tests at a
temperature of -20°C. In Part III, the test
specimens were confined at an elonga-
tion corresponding to 25% yield or break
strength during the freeze-thaw cycles
and then were tested at room tempera-
ture.
The paper describes the results of
each part of the study separately and
then investigates comparisons of Parts
I versus II and Parts I versus III. As of 50
freeze-thaw cycles, the tentative conclu-
sion is that neither geomembrane sheets
nor their associated seams are adversely
affected by the different conditions im-
posed. This tentative conclusion will be
further challenged after completion of
the 100 and 200 cycle testing.
This Project Summary was developed
by EPA's National Risk Management
Research Laboratory, Cincinnati, OH,
to announce key findings of the re-
search report that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
The effects of freeze-thaw cycling on
material durability should be a concern for
any type of engineered barrier material
installed in locations where ground freez-
ing conditions exist. Research has shown
that compacted clay liners (CCLs) become
friable and experience an increase in perme-
ability after only 10 to 15 freeze-thaw cycles
as observed by Zimmie and La Plante (1990).
Othman et al. (1993) have even found that
the hydraulic conductivity increased 10
times after a single cycle. Because of
such problems, CCLs are recommended
to be placed beneath the depth of maxi-
mum frost penetration. In the continental
United States, the frost depths range from
zero to 3.0 m. Frost depths are signifi-
cantly greater in Canada and Alaska. How-
ever, for alternate barrier materials such
as geomembranes, little information is
available regarding performance under
freeze-thaw cycling. Geomembranes are
almost always required by federal and
state regulations for use in landfill covers.
In freezing climates, geomembranes used
in landfill covers will be subjected to the
same freeze-thaw cycles as a CCL unless
the depth of cover soil is greater than the
maximum frost penetration depth. Other
geomembrane applications in which
freeze-thaw is a concern include: exposed
geomembrane liners in surface impound-
ments, dams and canals, and floating cov-
ers in reservoirs and other liquid impound-
ments. Thus, the impact of freeze-thaw
-------
cycles on the performance of geomembrane
sheets and seams should be investigated.
It should also be noted that tensile stress
may be induced when the geomembrane is
experiencing freeze-thaw cycles.
This paper presents the early part of
the test results from a geomembrane
freeze-thaw study which is a joint effort
between the Bureau of Reclamation and
the Geosynthetic Research Institute. The
focus of the study is to evaluate the ef-
fects of freeze-thaw on the tensile behav-
ior of 19 different geomembrane sheets
and 31 geomembrane seams. The study
consists of three parts. Part I involves
performing tensile tests at +20°C after
freeze-thaw cycling. Part II involves per-
forming tensile tests at -20°C after freeze-
thaw cycling. Part III involves performing
tensile tests at +20°C after freeze-thaw
cycling, but the test specimens are being
strained corresponding to 25% of their
yield or break strength during the freeze-
thaw cycling.
Literature Research
Although the effects of freezing of
geomembrane sheets and their seams is
an important issue, there is relatively lim-
ited published information available. Early
case studies were written about the per-
formance of synthetic liners for petroleum
facility containment dikes in Canada.
Thornton et al. (1976) visited seven sites
and inspected six types of liners in north-
ern Canada. They found that a polyethyl-
ene geomembrane which was installed in
-30°C weather and seamed by a hot air
welder was still in good condition. In addi-
tion, laboratory tests indicated that oil re-
sistant PVC remained ductile around -18°C,
but field experience showed that brittle frac-
tures were inflicted at temperatures as high
as 5°C. The report postulated that this
discrepancy may be the result of a shift in
the ductile-brittle transition temperature,
caused by increased strain from in situ
service loads. Laboratory testing was per-
formed only in unstressed conditions such
that the postulation has not been verified
experimentally under sustained loading in
combination with freezing.
Rollin et al. (1984) evaluated the tensile
behavior of synthetic and bituminous mem-
branes at temperatures of +23°C, -5°C,
-15°C, -25°C and -35°C. Their results
showed an increase in tensile strength
and a decrease in strain as temperatures
were decreased from 23°C to -35°C for
both sheet and seamed samples. Also
the seams appeared to behave satisfac-
torily at -35°C. LaFleur et al. (1985) stud-
ied the effects of freeze-thaw cycling on
5 geomembrane seams, but only 2 of
those seams are currently still available.
In their study, the seams were strained at
10% elongation, submerged in water and
ice and subjected to 150 freeze-thaw cycles.
No reduction occurred in any of the seam
shear strengths. In addition, they evaluated
the cold temperature seam strength of scrim
reinforced geomembranes. At -35°C, they
observed that the contribution of the fabric
scrim is not significantly altered in compari-
son to 23°C, confirming the observation
found by Allen et al. (1982). At -35°C the
stress/elongation behavior of the compos-
ite is mainly governed by the geomembrane
component. Although the above research
efforts do not show a fundamental concern
towards the freezing of geomembranes, the
development of a wide data base of cur-
rently used geomembranes and their seams
should be considered.
Test Materials and Incubation
Condition
A total of 19 different sheet materials
and 31 seam types were evaluated. The
total number of freeze-thaw cycles will
eventually be 200, however, this paper
only includes data up to 50 cycles. The
sheet and seam materials of all three parts
of the study are the same. They include
19 different geomembrane sheets and 27
seam types. In Part II, the number of test
materials was reduced to 6 different
geomembrane sheets and 13 seam types.
The types of geomembrane sheets and
seams that were used in each part of the
study are listed in Table 1.
Large sheet and seam samples (ap-
proximately 4 m long) were obtained from
various manufacturers. Test specimens
were died from the samples and were
either 25 mm wide by 200 mm long or
they were dumbbell shaped. They were
then put in polyethylene bags by groups
and were subjected to the freeze-thaw
cycles. A description of each test material
is also included in Table 1.
For Parts I and II the freeze-thaw cycles
were created by placing the specimens in
a household freezer set at -20°C for ap-
proximately 16 hr, and then removed to
room temperature conditions for approxi-
mately 8 hr. The ambient room tempera-
ture was approximately +20°C. All speci-
mens were initially dry. However, conden-
sation was observed on the surface of the
specimens during the thaw portion of the
cycles. Thus, the specimens experienced
some amount of wet-dry cycling, but to an
unknown and essentially uncon-
trolled amount.
The Part III specimens required
more elaborate incubation setup
than those of Parts I and II. Speci-
mens were confined by a metal
frame containing spaces for 25 mm
by 150 mm strips. Each specimen
was strained to a length corre-
sponding to 25% of its yield or
breaking strength. The seamed
specimens were placed in shear
mode while subjected to the elon-
gation. The entire metal frame, with
specimens, was enclosed within a
temperature controlled chamber.
The chamber was set to provide
freeze-thaw cycles of -20°C for 16
hr and +30°C for 8 hr.
Test Procedures
The experimental design for the
numbers of freeze-thaw cycles was
1, 10, 20, 50, 100 and 200. How-
ever, certain cycles were not per-
formed in Parts II and III of the study
because of a lack of materials and
time, as described in Table 2.
The full report was submitted in
fulfillment of Interagency Agreement
EPA Reference No. DW 14936139
between the U.S. Environmental Pro-
tection Agency and the U.S. Depart-
ment of the Interior, Bureau of Recla-
mation, under joint sponsorship.
-------
Table 1. Type of Geomembrane Sheets and Seams
Study
Part
1, II, III,
1, II, III
1,111
1,111
1, III
1, II, III
1, II, III
1, II, III
1, II, III
II
1, II, III
II
1, III
1,111
1,111
1,111
1, II, III
II
1, II, III
II
1,111
1, III
1,111
1,111
1, III
1,111
1, III
1, III
1,111
1, III
1,111
Geomembrane Type
(i.e. Polymer)
PVC-R
cold temperature formula
PVC
PVC
VLDPE
VLDPE
VLDPE
VLDPE
HOPE
HOPE
HOPE
HOPE
PP
PP-R
CSPE-R
EIA
EIA-R
FCEA
FCEA-R
EIA-R
Thickness*
mm
1.1
0.5
1.0
1.0
1.0
1.5
1.5
1.0
1.0
1.5
1.5
1.0
1.1
0.9
0.8
0.9
0.8
0.8
0.8
Style
Scrim reinforced
Smooth
Smooth
Smooth
Textured
Smooth
Textured
Smooth
Textured
Smooth
Textured
Smooth
Scrim reinforced
Scrim reinforced
Smooth
Scrim reinforced
Smooth
Geotextile supported
Scrim coated
Sheet Test
Specimen Shape
Strip
Strip
Strip
Dumbbell
Dumbbell
Dumbbell
Dumbbell
Dumbbell
Dumbbell
Dumbbell
Dumbbell
Dumbbell
Strip
Strip
Strip
Strip
Strip
Strip
Strip
Seam Type
Chemical
Hot Wedge
Chemical
Hot Wedge
Dielectric
Chemical
Hot Wedge
Dielectric
Hot Wedge
Fillet Extrusion
Hot Wedge
Fillet Extrusion
Hot Wedge
Hot Wedge
Hot Wedge
Hot Wedge
Hot Wedge
Fillet Extrusion
Hot Wedge
Fillet Extrusion
Hot Wedge
Hot Wedge
Chemical
Hot Air
Chemical
Hot Wedge
Chemical
Hot Wedge
Hot Air
Hot Air
Hot Wedge
* thicknesses are nominal values because this study consists of relative behavior within the same sheet or seamed material.
Key to Abbreviations
PVC = polyvinyl chloride
VLDPE = very low density polyethylene
HOPE = high density polyethylene
PP = flexible polypropylene
CSPE = chlorosulphonated polyethylene
EIA = ethylene interpolymer alloy
FCEA = fully cross/inked elastomeric alloy
T = textured
R = scrim reinforced
-------
Table 2. Number of Freeze-Thaw Cycles Performed in Each Part of the Study
Study
Part
1
II
III
0
C
c
C
1 5
C C
C
C
Freeze-Thaw Cycles
10 20
C
C
C
C
50
C
C
C
100
NC
NC
NC
200
NC
NC
NC
Note: C = complete and reported herein
NC = not complete at this time
A.I. Comer is with the U.S. Bureau of Reclamation, Denver, CO 80225; and M.L.
Sculli, and Y.G. Hsuan are with the Geosynthetic Research Institute, Drexel
University, Philadelphia, PA 19104.
David A. Carson is the EPA Project Officer (see below).
The complete report, entitled "Freeze-Thaw Cycling and Cold Temperature Effects
on Geomembrane Sheets and Seams," (Order No. PB96-177 175;
Cost: $31.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
26 W. Martin Luther King Drive
Cincinnati, OH 45268
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
EPA/600/S-96/004
------- |