What is Bitumen (Asphalt) Cutback Bitumen?
Bitumen is ‘cutback’ by adding controlled amounts of petroleum distillates such as kerosene. This is we do to reduce the viscosity of the bitumen temporarily. So it can penetrate pavements more effectively or to allow spraying at temperatures that are too cold for successful spraying sealing with neat bitumen. The materials we use to cutback bitumen will evaporate after application to leave the remaining material similar in hardness to the original bitumen.
Applications of Cutback Bitumen in Bituminous (asphalt) Pavement Construction and Maintenance:
Prime and Tack Coating
The process of priming involves applying a low viscosity binder that we prepare but usually unbound aggregate base. It is we intend that the top layers of the base to absorb . And provide a surface more easily ‘wetted’ by a subsequent bituminous covering. The primer will be able to carry traffic for a short time (although this practice is uncommon) and help control dust. Generally, we apply primers at rates between 0.5 and 1.4 L/m2. Cutback bitumens suitable for priming are also we use for tack coats, which we apply to an underlying surface to help with the adhesion of subsequent asphalt layer. A typical application rate is between 0.2 and 0.4 L/m2.
Where temperatures are too cool 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 pre-mix asphalt, which is used in patch repairs.
Cutback bitumens we use extensively in sprayed sealing applications. Particularly in cooler weather where they provide improved initial stone retention due to their lower viscosity. Typically, a single application of the appropriate cutback bitumen we spray onto the primed pavement. Onto which aggregate we laid.