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Henry Newman
Water resource engineer
Asked a question last year

What is difference between Asphalt and Bitumen?

What is difference between Asphalt and Bitumen?

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Flenn Hale
Construction Manager
What is difference between Asphalt and Bitumen?

In simple words, bitumen is a liquid that binds together asphalt.

Asphalt-It is a mixture prepared by adding aggregates(sand, gravel, slag, crushed rocks) with appropriate binders like bitumen. Then it is laid down on-site to a decided level or thickness by a paving machine.

Bitumen- This is the heavy semi-solid hydrocarbon produced by the distillation of crude oil.

Nothing. They mean the same thing from a civil engineering perspective, strictly speaking.

But, sometimes people say they're different because they misunderstand asphalt concrete or Hot mix asphalt (HMA) as asphalt, which is wrong.

Also, from a petroleum engineer's point of view, they are actually different. Bitumen is the naturally occurring material found as a residue in crude oil distillation, and asphalt is the same thing manufactured in a plant.

What is difference between Asphalt and Bitumen?

Bitumen is a residue of crude oil distillation occurs naturally. It is a semisolid hydrocarbon which is heavy in mass.

Asphalt is produced in the plant by mixing of fine sand, coarse sand, bitumen, gravel, and slag.

These are two materials used to construct a bituminous pavement in road construction. Where bituminous is a binding material for asphalt.

In bituminous pavement, bitumen spread over the pavement and then covered with fine aggregates.

Currently, rigid concrete pavements should be preferred over bituminous pavement due to its high durability and high strength.

  1. Tar And Bitumen
  • Tar: No longer used for road construction because of its *Carcinogenic Effect and high temperature susceptibility. Presently, roads are mostly constructed using Bitumen.
  • Reason For Confusion Between Tar and Bitumen: Both have black color and both have very good Waterproofing and adhesion property.
  • Production Method:
    • Tar→ From Destructive Distillation (Burning in Specific Condition of Temperature, Without Presence of Oxygen) of Bituminous Coal
    • Bitumen→ Obtained From Refining Process (Fractional Distillation) of Crude Oil (A Petroleum Product)

* For Manufacturing of Tar, Coal is Burnt Without Presence of Oxygen. This induces formation of specific molecules called Polyclic Aromatic Hydrocarbons [PAH] which are carcinogenic.

(PAH represent 20–30% Composition of Tar. That’s the Reason the Use of Tar is Banned in Most Countries.)

[PAH is also present in Bitumen. But only approximately 0.01%. So, it is not carcinogenic]

2. Bitumen and Asphalt:

  • In India and Europe, Asphalt = Aggregates + Bitumen i.e. Paving Material
  • In America, Asphalt = Bitumen (Black Viscous Liquid)

Bitumen is actually the liquid binder that holds asphalt together. A bitumen sealed road has a layer of bitumen sprayed and then covered with an aggregate. This is then repeated to give a two-coat seal. Asphalt is produced in a plant that heats, dries and mixes aggregate, bitumen and sand into a composite mix.