Bitumen Cutback
Cutback bitumen products are preparations of standard grade bitumen and a solvent (usually kerosene) used to reduce the viscosity of the bitumen. Cutbacks are typically used in sprayed sealing applications and deferred set or cold mixtures.
Application
Priming & Tack Coating
The process of priming involves applying a low viscosity binder to a prepared but usually unbound aggregate base. It is intended to be absorbed by the top layers of the base and provide a surface more easily ‘wetted’ by a subsequent bituminous covering.
Cutback bitumen suitable for priming is also used for tack coats, which are applied to an underlying surface to help with the adhesion of subsequent asphalt layer. Better performance at low temperatures. Greater resistance to aging. Improvement in storage stability.
Primer Sealing
Where temperatures are too cold for an effective priming operation, or where traffic is likely to upset a primed surface before the final seal can be sprayed, a primer seal can be used to give adequate protection of the pavement for periods of up to 6 to 12 months. Cutback bitumens suitable for primer sealing can also be used in the manufacture of premix asphalt, which is used in patch repairs.
Sprayed Sealing
Cutback bitumen is used extensively in sprayed sealing applications, particularly in colder weather where they provide improved initial stone retention due to their lower viscosity. Typically, a single application of the appropriate cutback bitumen is sprayed onto the primed pavement onto which aggregate is laid.
