Contents

Main Page
Manufacture of Asphalt Roofing Products
Occupational Exposure to Asphalt Fumes
Guidelines for Protecting Workers
References
Abbreviations
Glossary
Appendix

Glossary

Air-blowing: The manufacturing process used to make oxidized roofing asphalts in which air is blown through an asphalt flux. 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) The product of the nondestructive distillation of crude oil in petroleum refining; it is a dark brown to black, cement-like semisolid or solid. Depending on the crude oil used as a feed-stock, 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 of atmospheric and vacuum distillation processes used by petroleum refineries and independent asphalt manufacturers; used in the manufacture of some asphalt roofing materials (e.g., saturant asphalts, some modified bitumen products); 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].

Blowing still: A closed-process vessel fitted at its base with a sparger and used in the air-blowing process to make many types of roofing asphalt.

Built-up roofing (BUR): A system of asphalt-impregnated felt plies sealed and surfaced with hot mopping-grade asphalt; primarily used in low-slope commercial roofing. The felt plies can be organic (e.g., cellulose), fiberglass screen or mat, or polyester fabric.

Coating 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.

Modified bitumen: 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 BUR 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 BUR systems, organic felt shingles, and other roofing materials such as roll roofing.

Straight-run asphalt: The residuum of atmospheric and vacuum distillation processes used in petroleum refineries and by independent asphalt manufacturers. This asphalt is used in the manufacture of some asphalt roofing materials (e.g., saturant asphalts, some modified bitumen products); it is also used as a feedstock in the air-blowing process used to make oxidized roofing asphalt.