Bituminous Materials

Bituminous Materials

Bitumen is a viscous liquid or semi-solid form of petroleum that is black and sticky. It is used primarily in road construction as a binder for aggregates.

Asphalt Cement (AC)

Asphalt cement is refined bitumen produced by fractional distillation of crude oil.

• Viscosity: Resistance to flow. Temperature dependent.
• Penetration Grade: Based on penetration test at 25°C.
• Viscosity Grade: Based on viscosity at 60°C.
• Performance Grade (PG): Based on rheological properties over a range of temperatures (Superpave).

Cutbacks and Emulsions

• Cutback Asphalt: Asphalt cement dissolved in a solvent (gasoline, kerosene, diesel).
  • Rapid Curing (RC): Gasoline.
  • Medium Curing (MC): Kerosene.
  • Slow Curing (SC): Diesel.
• Asphalt Emulsion: Asphalt cement dispersed in water with an emulsifying agent.
  • Anionic (negative charge).
  • Cationic (positive charge).

Marshall Mix Design Method (ASTM D6926)

The objective is to select the asphalt binder content that satisfies stability and flow requirements.

Common Tests

• Penetration Test (ASTM D5): Hardness/Consistency.
• Viscosity Test (ASTM D2170/D2171): Flow characteristics.
• Ductility Test (ASTM D113): Ability to stretch.
• Flash Point Test (ASTM D92): Safety temperature limit.
• Softening Point Test (Ring and Ball - ASTM D36): Temperature at which bitumen softens.