Geosynthetics June/July 2023 - 18

Powering through extremes: Fuel containment in Moose Creek
temperature, and then bended around a
specified radius.
This test is a two-dimensional meaFIGURE
12 Fuel tank at Moose Creek.
Photo courtesy of Latitude 63
traffic is expected. This was one of the
reasons the arctic-grade geomembrane
was chosen, as its long-term cold flexibility
will accommodate flexing at extremely
low temperatures, which is needed for
arctic operations.
There are primarily
two widely used
laboratory tests
to measure cold
weather workability
for geomembranes:
one is a bend test
and the other is an
impact test.
Dynamic cold testing
Geomembrane systems are used worldwide
in all environments. That includes
hot- and cold-temperature applications,
and both extremes present their own
challenges. Laboratory test data provides
guidance on material properties that will
tell us which products are candidates for
certain applications. Cold weather workability
is one of those situations.
There are primarily two widely used
laboratory tests to measure cold weather
workability for geomembranes: one is a
bend test and the other is an impact test.
While the challenge lies in the interpretation
of the results of each test, the tests
themselves are quite different.
ASTM D2136, Standard Test Method
for Coated Fabrics-Low-Temperature
Bend Test (Low-Temp Bend). A geomembrane
specimen is placed in
a bending jig, lowered to a specified
18
Geosynthetics | June July 2023
sure of bending at low temperatures. It
is repeatable and largely not operator
influenced, as the bend action is accomplished
by the jig falling by its own weight
rather than by hand. Variability exists
in the diameter, or radius, of the bend.
Generally, the larger the radius, the lower
the temperature at passing with no cracking,
which can vary by manufacturer.
In the field, multidirectional handling
or loading of a geomembrane during
installation or at other loading can create
cracking at temperatures higher than
those found in the laboratory. Merely
walking on a geomembrane applies load
in three dimensions.
ASTM D746, Standard Test Method
for Brittleness Temperature of Plastics and
Elastomers by Impact (Low-Temp Impact).
Also designated brittleness temperature,
the test measures the temperature at which
50% of the tested specimens exhibit brittle
failure at specified impact conditions.
It is utilized primarily for plastics and
elastomers. Specimens are secured in a
testing apparatus, lowered to a specified
temperature, and then struck at a specified
linear speed. ASTM says, " The test
provides for the evaluation of long-term
effects, such as crystallization, or those
effects introduced by incompatibility of
plasticizers in the material under test. "
The test is only 50% accurate at the
outset, establishing a temperature at a
50% passing. In the geomembrane industry,
this test method applies primarily
to rigid products that are not subject to
bending, and thus the method receives
limited attention. Rigid geomembranes
are not likely to be installed or flexed
at extremely low temperatures, so an
impact, or a breakage, is the closest estimate
of cold weather workability. Lab to
field scale-up would be difficult, but this
test does give some starting parameters.
Geosynthetics June/July 2023

Table of Contents for the Digital Edition of Geosynthetics June/July 2023
