bitumen 1

Pavement Materials

Types of Materials

• Bitumen or Asphalt

• Aggregates

• Bituminous Mix or Asphalt Mix

Bitumen Vs Tar

• Bitumen

  • Petroleum product obtained by the distillation of petroleum crude (fractional distillation).

  • By-product of crude oil refinery.

• Tar

  • Produced from coal through destructive distillation (applying high pressure and temperature).

Types of Bitumen or Asphalt

• Asphalt Emulsion

• Asphalt Cutback

• Foamed Asphalt

Emulsified Asphalt

• Definition

  • A suspension of small asphalt cement globules in water assisted by an emulsifying agent (like soap).

• Function of Emulsifying Agent

  • Imparts an electrical charge to prevent globules from coalescing.

• Uses

  • Reduces asphalt viscosity for lower temperature applications (e.g., tack coats, fog seals, slurry seals, bituminous surface treatments, stabilization).

• Types

  • Anionic (negatively charged asphalt droplets).

  • Cationic (positively charged asphalt particles).

Bitumen Emulsion Components

• Main Components

  • Bitumen

  • Other Components (e.g., water, emulsifier)

• Process

  • Mixed using a colloid mill and heater.

Cutback Asphalt

• Definition

  • A combination of asphalt cement and petroleum solvent.

• Function

  • Reduces viscosity for lower temperature uses (similar to emulsions).

• Curing Process

  • The petroleum solvent evaporates after application, leaving behind asphalt cement residue.

Foamed Asphalt

• Formation

  • Created by combining hot asphalt binder with small amounts of cold water.

• Process

  • Cold water turns to steam upon contact with hot asphalt, forming bubbles.

• Characteristics

  • High volume foam with approximately 10 times more coating potential than liquid asphalt.

  • Thin-film state lasts only for a few minutes before reverting to original properties.

• Uses

  • Binder in soil or base course stabilization, full-depth asphalt reclamation.