Bitumen

A solid material or viscous liquid that is dark brown or black in colour, and provides adhesive properties.

Bitumen essentially consists of hydrocarbons, derived from petroleum. Cut-back bitumen is bitumen whose viscosity has been reduced by the addition of a suitable volatile dilutant or flux. Normal grades used - 50, 100, 200 secs. Straight run bitumen is obtained after the final stage of distillation of crude oil of a suitable type. Normal grades used - 50 pen (hard) to 300 pen (soft).