GLOSSARY
Air blowing: The manufacturing
process in which air is blown through an asphalt flux to make oxidized
roofing asphalts. An exothermic oxidation reaction occurs, yielding
an asphalt that is harder, more viscous, less volatile, and less temperature-susceptible
than the asphalt flux used as the feedstock to the process.
Asphalt (CAS number 8052–42–4):
A dark brown to black, cement-like semisolid or solid that is the
product of the nondestructive distillation of crude oil in petroleum
refining. Depending on the crude oil used as a feedstock, the distillation
residuum may be further processed, typically by air-blowing (sometimes
with a catalyst) or solvent precipitation to meet performance specifications
for individual applications [AI 1990b]. Asphalt is a mixture of
paraffinic and aromatic hydrocarbons and heterocyclic compounds
containing sulfur, nitrogen, and oxygen [Sax and Lewis 1987].
Asphalt, cutback:
An asphalt liquefied by the addition of diluents (typically petroleum
solvents) [AI 1990b; Roberts et al. 1996; Speight 1992].
Asphalt flux:
The residuum (heated sufficiently to flow) that results from the
atmospheric and vacuum distillation processes used by petroleum
refineries and independent asphalt manufacturers. Asphalt flux is
used in the manufacture of some asphalt roofing materials such as
saturant asphalts and some modified bitumen products. Asphalt flux
is also used as a feedstock in the air-blowing process used to make
oxidized roofing asphalt.
Asphalt fumes: The
cloud of small particles created by condensation from the gaseous
state after volatilization of asphalt [NIOSH 1977].
Asphalt, oxidized-blown or air-refined
(CAS number 64742–93–4): Asphalt treated
by blowing air through it at elevated temperatures to produce physical
properties required for the industrial use of the final product.
Oxidized asphalts are used in roofing operations, pipe coating,
undersealing for Portland cement concrete pavements, hydraulic applications,
membrane envelopes, some paving-grade mixes [AI 1990b], and the
manufacture of paints [Speight 1992].
Asphalt, roofing:
Asphalt that is refined or processed to meet specifications for
roofing.
Built-up roofing (BUR):
A system of asphalt-impregnated felt plies sealed and surfaced with
hot mopping-grade asphalt. BUR is primarily used in low-slope commercial
roofing. The felt plies can be organic (e.g., cellulose), fibrous
screen or mat, or polyester fabric
Coating-grade asphalt:
An air-blown or oxidized asphalt used to manufacture roofing materials
used in a variety of roofing systems such as asphalt shingles, polymer-modified
bitumen roofing, reinforcing and underlayment felts, and roll roofing
products.
Fire point: The lowest
temperature at which a substance can give off vapors fast enough
to support continuous combustion. The fire point is often 5EF (2.8EC)
above the flash point [NSC 1996].
Flammable or explosive limits:
Lower flammable or explosive limit (LEL): The minimum airborne concentration
of a flammable substance needed to propagate a flame after contact
with an ignition source (i.e., the concentration below which the
mixture is too lean to propagate a flame) [NSC 1996].
Upper flammable or explosive limit
(UEL): The maximum airborne concentration of a flammable
substance that will permit propagation of a flame on contact with
an ignition source (i.e., the concentration above which the mixture
is too rich to propagate a flame) [NSC 1996].
Flash point: The
lowest temperature at which a substance can give off enough vapors
to form an ignitable mixture with air and produce a flame if an
ignition source is also present [NSC 1996].
Flood coat: The surfacing
layer of asphalt into which surfacing aggregate is embedded on an
aggregate-surfaced built-up roof. A flood coat is generally thicker
and heavier than a glaze coat and is applied at approximately 45
to 60 lb/100 ft2 (2 to 3 kg/m2).
Modified bitumen system: A
roofing system based on membranes manufactured by impregnating or
coating one or more fabric plies with a straight run or oxidized
asphalt modified using a polymer, usually atactic polypropylene
(APP) or styrene-butadiene-styrene (SBS). Modified bitumen systems
may be torch-applied or installed by adhesion in hot asphalt or
a cold-applied, solvent-based asphalt adhesive (cutback asphalt).
Modified bitumen systems are used on low-slope (primarily commercial
or industrial) roofs.
Mopping-grade asphalt:
An oxidized asphalt used principally in the construction
of built-up roofing and some modified bitumen systems; mopping-grade
asphalts are produced in four grades (Types I through IV), according
to the steepness of the roof.
Saturant asphalt:
A nonoxidized or oxidized asphalt, typically an AC-10 or AC-20 grade
material, used to manufacture saturated organic felt plies used
in the construction of built-up roofing systems, organic felt shingles,
and other roofing materials such as roll roofing.
Straight-run asphalt: The
residuum of atmospheric and vacuum distillation processes used by
petroleum refineries and independent asphalt manufacturers. This
asphalt is used in the manufacture of some asphalt roofing materials
(e.g., saturant asphalts and some modified bitumen products); it
is also used as a feedstock in the air-blowing process used to make
oxidized roofing asphalt. |
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