ASTM D8008-20

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Designation: D8008 − 15 D8008 − 20
Standard Practice for
Representative Field Sampling of Traffic Paints
This standard is issued under the fixed designation D8008; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers procedures for obtaining representative field samples of mixed or unmixed waterborne, solventborne,
or other liquid traffic paints paints, including two component reactive materials from drums, totes, or machine striping tanks. Traffic
paint samples are often taken from storage containers in the field by paint suppliers or government agencies for laboratory testing
to determine product quality and/or for approvals prior to striping. It is important that the samples taken are “representative” (have
a composition reflecting the overall composition in the container). Although traffic paints can remain homogeneous for weeks or
months, some will stratify over time and become non-homogeneous. Obtaining a representative sample can be challenging
particularly in a field environment. The desired method for obtaining a liquid sample is to thoroughly mix the sample until
homogeneous and then sample the mixture from the top. If complete mixing can’t be verified then an alternative practice is to
obtain a sample using a liquid tube sampling device. These devices have the ability to capture a top-to-bottom core of paint from
the container. Inner or outer rod tube samplers are recommended for sample extraction. The inner rod tube sampler is the preferred
sampler.
1.2 The practice selected for representative sampling should have written agreement between the parties providing the product
and those testing the product.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D562 Test Method for Consistency of Paints Measuring Krebs Unit (KU) Viscosity Using a Stormer-Type Viscometer
D1475 Test Method for Density of Liquid Coatings, Inks, and Related Products
D3925 Practice for Sampling Liquid Paints and Related Pigmented Coatings
D5495 Practice for Sampling With a Composite Liquid Waste Sampler (COLIWASA)
2.2 ISO Documents:
ISO 1513 Paints and varnishes — Examination and preparation of test samples
ISO 15528 Paints, varnishes, and raw materials for paints and varnishes — Sampling
3. Terminology
3.1 The following terms apply to this practice:
This practice is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.44 on Traffic Coatings.
Current edition approved July 1, 2015June 1, 2020. Published August 2015July 2020. Originally approved in 2015. Last previous edition approved in 2015 as D8008 – 15.
DOI: 10.1520/D8008-15.10.1520/D8008-20.
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D8008 − 20
3.1.1 COLIWASA (composite liquid waste sampler), n—a tube type device that is typically used as a zone sampler for many
types of liquids.
3.1.2 composite core sampler, n—a compartmented tube type sampler that is potentially capable of obtaining a representative
core sample.
3.1.3 core sample, n—a sample extracted from a container top-to-bottom with a tube type device.
3.1.4 liquid scoop, n—a type of liquid thief sampler with compartments and slide closure that potentially can be used to obtain
a representative core sample
3.1.5 liquid thief sampler, n—a tube or scoop device used to extract a liquid sample.
3.1.6 pigment settling/pigment sedimentation, n—increase in pigment concentration toward the bottom of a container over time
mainly due to the effects of gravity.
3.1.7 representative sample, n—a paint sample taken from a thoroughly mixed container, or a paint sample taken by suitable
means from a partially mixed or unmixed container that has a composite composition equivalent to that of a thoroughly mixed
container.
3.1.8 stratification, n—separation of a mixture of materials into layers based on density.
3.1.9 syneresis, n—a clear liquid separation at the top of a paint typically resulting from movement of lower density continuous
phase components upward in a paint.
3.1.10 uniform sample, n—see representative sample.
3.1.11 water float, n—small amount of water added to the top of a tote or drum of fast-dry waterborne traffic paint to prevent
skinning.
3.1.12 zone sampler, n—a sampling device that samples from a selected location within a container; a zone sampler produces
a non-representative sample unless the container contents are homogeneous.
4. Summary of Practice
4.1 This practice provides methods for obtaining “representative” traffic paint samples from storage containers in the field.
4.2 Traffıc Paint—Traffic paints are essentially pigment dispersions consisting of a continuous phase, a polymeric binder, finely
ground pigments (typically white or yellow), and various additives in small amounts such as a pigment dispersant, thickener,
defoamer, and biocide. The continuous phase in a typical waterborne traffic paint is water with smaller amounts of methanol and/or
coalescing solvent, and the binder is a synthetic latex. The continuous phase for solventborne traffic paint is one or more organic
solvents, and the binder is typically an alkyd resin. In this document, traffic paint can also reference two component pavement
marking materials such as epoxy, modified epoxy, and polyurea which require the mixing of a pigmented resin portion with a
non-pigmented catalyst portion at closely controlled, specified proportions immediately prior to application onto the pavement.
4.3 Traffıc Paint Containers—The paint containers most often sampled in the field are drums, totes, or striping machine tanks.
Common traffic paint tote sizes are 250 gal (946 L), 275 gal (1040 L), or 330 gal (1249 L), and they are typically of plastic (poly)
or stainless steel construction. The heights of standard containers are: 55 gal drums, 34 inin. (86 cm); 250 gal totes, 40 in. (102
cm); 275 gal totes, 46 in. (117 cm); and 330 gal totes, 54 in. (137 cm). Striping tank containers vary in size. Tube type sampling
devices should be long enough to reach the bottom of the container being sampled.
4.4 Field Sampling—Government agencies such as Departments of Transportation (DOTs) often conduct field sampling of
traffic paints from containers for laboratory testing to determine the paint’s conformity to specifications and for approval before
application to a roadway. Suppliers also sometimes sample field containers if there is an issue reported or a quality check is needed.
The sample size typically required for laboratory testing is on the order of about 1 qt to 1 gal (1 to 4 L).
4.5 Change in Paint Composition over Time—Like most other types of liquid paints, traffic paints are very uniform when first
made in production and also initially in the storage containers when shipped out into the field for striping. The paints can be very
stable and homogeneous for weeks or months. However, depending on a paint formulation’s inherent stability, the paint’s viscosity,
its storage environment (internal and external), and time in storage, traffic paint in a container may change composition from top
to bottom over time. The change in paint uniformity within a container is often simply due to the effect of gravity resulting in the
gradual downward settling or sedimentation of the more dense pigments and/or migration of lower density continuous or disperse
phase components upward toward the surface. Pigment settling is minimized in the production of traffic paint with a sufficient grind
(reduction of pigment particle size), proper stabilization (with optimized dispersants and surfactants) and also by increasing the
viscosity of the paint to within specification with a thickener. An eventual non-homogeneous composition of paint within a
container is often a vertical gradient distribution of pigment with a corresponding gradient change in solids content (lower at the
top and higher at bottom of the container). Over time, this can produce soft settling at the bottom of the container, or in more
extreme cases, hard settling (compaction) may occur. Sometimes the continuous phase components (solvents or water) being of
lower density can migrate upward toward the surface of the container eventually resulting in a clear liquid separation at the top
(syneresis). Another contributor to non-uniformity of waterborne traffic paint in a container is the common practice of adding a
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small “water float” on top of the paint after filling to prevent skinning. Paint in containers exposed to extreme heat, to long periods
of elevated temperature, or to one or more freeze-thaw cycles may have accelerated compositional changes. Obtaining
representative samples from non-homogeneous paint containers are addressed in this practice.
4.6 Sampling Methods—Practice D3925 addresses procedures for the mixing of liquid paints of any type and in most any size
container to obtain representative samples for testing. In that method, thorough mixing of the paint is verified when densities match
for zone samples taken from the top and bottom of the container. With the availability of appropriate mixing equipment and a
suitable power source, the procedures in Practice D3925 can be used for sampling traffic paint in the field. Since sample uniformity
is assured when thorough mixing is achieved, this is a preferred option. However, mixing is often not practical or even possible
in a field environment, and complete mixing may not be verifiable. In this situation, an alternative preferred practice is to obtain
a representative sample using a liquid thief device that has the ability to capture a top-to-bottom core of paint that is representative
when homogenized. The core sample would include any water float but would typically not include any hard sediment if present.
ISO 15528 provides general procedures and various types of devices for sampling liquids and solids. However, many of the
sampling devices described in ISO 15528 are zone samplers and therefore not capable of capturing a representative paint sample.
This practice describes the particular issues involved with the field sampling of traffic paint and best practices for obtaining
representative samples from mixed or unmixed containers.
5. Significance of Practice
5.1 For quality assessment and/or approval for use of traffic paint stored in the field, it is often necessary to obtain a
representative sample for testing. Correct sampling of traffic paint is a skilled operation, and if not properly conducted with the
right equipment and procedures, a sample may inadvertently fail one or more specification tests when evaluated by a testing
laboratory. Among the test results that could be affected are solids content, resin content, TiO content, heat-age stability,
freeze-thaw stability, and dry time. Any of these could inadvertently result in non-approval or penalties.
6. Apparatus and Procedures
6.1 Sampling from Thoroughly Mixing Containers:
6.1.1 Thorough Mixing with Verification—A most preferred practice for obtaining a representative sample from a container is
thorough mixing of the container contents prior to sampling. Practice D5495 provides guidelines for types of mixers, sample
removal, and verification for thorough mixing. Some types of mixers that can be used are impellers, drum rollers, and drum
shakers, or the practice of “boxing” where fluid is pumped back and forth between containers for mixing. With Practice D5495,
complete mixing is indicated when a sample pulled from the top of a container has a density very close to a sample pulled from
the bottom of the container within 0.5 lb/gal (60 g/L). Density is typically determined using a weight/gal cup in accordance with
Test Method D1475. If available, efficient mixing can be accomplished using a high speed portable drum or tote mixer. The mixer
should have sufficient power, large impeller blades, and shaft long enough to reach the bottom of the container and ideally into
the corners of the container. A small blade mixer or under-powered mixer may not produce enough mixing action to efficiently turn
over the contents of the container. The mixer can be driven by air, electricity, or hydraulics but should be appropriate for efficiently
moving viscous fluids (traffic paints) of moderately high viscosity. Traffic paint viscosity is commonly measured with a Stormer
Type viscometer using Practice D562, and a typical viscosity range is 75 to 95 Krebs Units (KU). Over time, the viscosity of traffic
paint can increase or decrease during storage, and the viscosity near top of the container may be different (usually lower) than that
near the bottom.
6.1.2 Samplers for Thoroughly Mixed Containers—If there is assurance (by density comparison or other means) that a
container’s contents have been thoroughly mixed, a representative sample can be removed using a wide variety of sampling devices
from most any location within the container. One such device is a zone sampler. The zone sampler takes a sample from a single
location within a container. The recommended sampling location for zone sampling of a thoroughly mixed container is near the
horizontal/vertical center of the container. As noted in 6.1.1, zone samples taken from top and bottom will confirm homogeneity
with a density match. Some common examples of zone samplers are bottle or can samplers, dip samplers, or bottom zone samplers
as shown in ISO 15528 sections 5.1.4 and 5.15. Various tube type samplers such as a COLIWASA can also be used as zone
samplers.
6.1.3 Sampling from an Outlet Valve—If there is an outlet valve at the bottom of the container (some totes and tanks), a
thoroughly mixed container can be sampled through this port. When sampling from an outlet valve, some paint, about 5 gal (about
20 L) should first be drained from the container into a clean bucket before getting the final sample for testing. The usual sample
size for testing is approximately 1 qt to 1 gal (1 to 4 L). Any drained material in the bucket not used for testing can be returned
to the top of the container.
6.2 Sampling from Unmixed Containers or when Mixing might be Incomplete:
6.2.1 Often it is not possible to conduct mixing of field drums, totes, or striping tanks before obtaining a sample for testing. In
those instances, a tube or closed scoop sampling device that has the ability to capture a representative
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