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.