What are the cited sources of asphalt?

• A. Coal tar and creosote
• B. Natural asphalt deposits and petroleum asphalts
• C. Synthetic polymers
• D. Plant resins and varnishes

Answer: (B)

Asphalt binder for paving mainly comes from two sources: natural asphalt deposits and petroleum asphalts. Natural asphalt occurs as viscous bitumen in deposits or seeps around the world and can be processed into a usable binder. Petroleum asphalts come from refining crude oil; the heavy fractions recovered after distillation are processed (sometimes oxidized or blown) to form the asphalt used in pavements. The other options aren’t typical sources for road asphalt—coal tar and creosote come from coal processing and aren’t standard asphalt binders; synthetic polymers are added to modify asphalt, not serve as the primary source; plant resins and varnishes are unrelated.