Asphalt refers to varieties of naturally occurring bitumen. Asphalt is also produced as a petroleum byproduct. Both substances are black and largely soluble in carbon disulfide. Asphalts are of variable consistency, ranging from a highly viscous fluid to a solid.
Asphalt is derived from petroleum in commercial quantities by removal of volatile components. It is an inexpensive construction material used primarily as a cementing and waterproofing agent.
Asphalt is composed of hydrocarbons and heterocyclic compounds containing N2, sulfur, O2; its components vary in molecular weight from about 400 to 5000. It is thermoplastic and viscoelastic; at high temperatures or over long loading times it behaves as a viscous fluid; at low temperatures or short loading times as an elastic body.
The three distinct types of asphalt made from petroleum residues and their uses are described in Table A.14.
|
Asphalt Type and % of Production |
Manufacturing Process |
Properties |
Uses |
|
Straight-run, 70-75% |
Distillation or solvent precipitation |
Nearly viscous flow |
Roads, airport runways, hydraulic works |
|
Air-blown, 25-30% |
Reacting with air at 204-316°C |
Resilient: viscosity less susceptible to temperature change than straight-run |
Roofing, pipe coating, paints, underbody coatings, paper laminates |
|
Cracked, less than 5% |
Heating to 427-538°C |
Nearly viscous flow; viscosity more susceptible to temperature change than that of straight-run asphalt |
Insulation board saturant, dust laying |
