Geoscience Reference
In-Depth Information
Table B.3
Basic materials for geotextiles and prescribed
durability tests for up to 25 years design life.
Material
Test
Polyester (PET)
Hydrolysis, ENV 12447
Polypropylene (PP)
Oxidation test, ENV ISO 13438
Polyethylene (PE)
Oxidation test, ENV ISO 13438
The materials from which geotextiles are normally made, polyester (polyethylene
terephthalate), polyethylene, and polypropylene, or combinations thereof, are suffi-
ciently durable for structures with a lifetime shorter than five years and thus require
no further testing. This applies to all applications, with the exception of sustainable
reinforcement, on condition that the pH value (acidity level) of the soil lies between
4 and 9 and that no recycled geotextile is used.
For structures with a lifetime of up to 25 years, supplementary durability tests
are required, see Table B.3. The product is suitable if more than 50% of the original
strength is retained after completion of the test.
The European standard also allows the durability to be determined based on
experiences with comparable products (both raw materials and processing) under
similar circumstances. Furthermore, the durability annex of the standard describes
ground situations with a high or low pH and other specific circumstances that are
normally not relevant for geotextile-encapsulated sand elements.
LONGER LIFETIME
Structures in which geotextiles are used are often designed for a lifetime considerably
exceeding 25 years and experience suggests that such structures are easily capable of
longer design lives. That the standard does not go beyond 25 years does not mean that
the structures cannot exceed this period but that the durability cannot be accurately
assessed using these rather general procedures. Also of importance is the biological
activity in the ground. This is an area where assessments can be made based on experi-
ence and where data and no general guidelines exist.
In practice, sometimes two extreme positions are taken of which both are incor-
rect. On the one hand the durability of a structure exceeding 25 years may be doubted,
with the argument that such a period is not contained in the standards. This position
is unjustified since experience of lifetimes greater than 30 years have revealed little
geotextile ageing. On the other hand, a lifetime of 150 years (or more) is sometimes
claimed on the basis of an oxidation test alone.
Today, some specialized laboratories can do durability tests that prove the lifetime
of a geotextile can be longer than the lifetimes mentioned above. Their results show
that by using specific polymer additives long lifetimes are possible.
