ASTM G160-98

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: G 160 – 98
Standard Practice for
Evaluating Microbial Susceptibility of Nonmetallic Materials
By Laboratory Soil Burial
This standard is issued under the fixed designation G 160; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.3 This practice may be considered an inoculation with a
mixed culture of fungi and bacteria.
1.1 This practice is limited to the method of conducting an
evaluation of a nonmetallic material’s microbiological suscep-
3. Soil
tibility when in contact with the natural environment of the soil
3.1 Composition— Soil shall be composed of equal parts of
and is intended for use on material test specimens that are
2 2
fertile topsoil (soil with a high clay content should not be
approximately 2 cm ( ⁄4 in.) thick and 100 cm (20 in. ) or less.
used), well-rotted and shredded horse manure, and coarse sand
This practice may be applied to articles that do not spend the
(10 to 40 mesh).
majority of their service life in soil.
3.2 Mixing—The soil composition of 3.1 should be pre-
1.2 A wide variety of properties may be affected by micro-
pared by simple mixing and sifting through ⁄4-in. mesh screen.
bial attack depending on material or item characteristics.
3.3 Aging—The mixture is aged for three months and
Standard methods (where available) should be used for each
resifted twice at four-week intervals during the three months.
different property to be evaluated. This practice does not
After three months, a viability control of untreated cotton cloth,
attempt to enumerate all of the possible properties of interest
2 2
400 to 475 g/m (12 to 14 oz/yd ), buried in the soil shall have
nor specify the most appropriate test for those properties. Test
a tensile strength loss of at least 50 % after five days.
methods must, however, be appropriate to the material being
tested.
NOTE 1—The soil mixture may be used for sequential tests as long as
1.3 It is recommended that this practice be combined with the cotton cloth control degrades within the specified time period.
appropriate environmental exposures (for example, sunlight
3.4 pH—The soil shall have a pH between 6.5 to 7.5,
simulating weathering devices, the hydrolytic effects of ex-
checked periodically, and maintained by the addition of ground
tended aqueous contact, or extraneous nutrients) or fabrication
limestone to raise the pH or flowers of sulfur to lower the pH.
into articles (for example, adhesive bonding of seams) which
The soil pH may be taken by dispersing 1 weight part soil in 20
may promote microbiological susceptibility during the service
parts of water, shaking or stirring, then allowing the mix to
life of the material.
settle for 1 h. The pH is measured with indicator paper,
1.4 The values given in parentheses are provided for infor-
electrodes, or by titration.
mation purposes only.
3.5 Moisture—The soil shall be maintained at between 20
and 30 % moisture, based on the dry weight of the soil. (The
2. Significance and Use
percent moisture is calculated by weighing approximately 50
2.1 These results may be used to compare the susceptibility
mL of a representative portion and taking the portion to
of materials when exposed to this test procedure.
constant weight by placing the soil in an oven at a temperature
2.2 Microbiological susceptibility may be reflected by a
of 101 to 106°C.) Water lost during use as a result of
number of changes including staining, weight loss, or reduction
evaporation shall be replaced without deforming the soil bed. If
in tensile or flexural strength.
the surrounding atmosphere is maintained at 85 to 95 %
relative humidity, this loss is negligible, however, the moisture
level should be periodically measured.
This practice is under the jurisdiction of Committee G-3 on Weathering and
Durability and is the direct responsibility of Subcommittee G03.04 on Biological
Deterioration.
Current edition approved Nov. 10, 1998. Published April 1999. Originally
published as G 160–98.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
G 160
4. Apparatus 9. Calculation and Interpretation of Results
4.1 Soil Container— The container shall be any material of
9.1 Visual—At the end of the exposure period, the speci-
suitable mechanical strength and chemical/microbial resistance
mens shall be removed from the soil bed and conditioned
and, if porous, shall be lined with impermeable material. It
according to methods appropriate to the material being tested.
shall be of any size that is convenient to handle and having a
For visual evaluation, the material is rinsed under a stream of
depth of at least 12.7 cm (5 in.).
tap water while gently rubbing between fingers to remove soil
4.2 External Environment—An apparatus capable of main-
and air-drying at 20°C (68°F) for minimum amount of time.
taining a temperature of 30 6 2°C (86 6 3.6°F) and a relative
Alternatively, the material may be gently vacuumed or very
h
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