Priming and Tack Coating

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Bitumen is ‘cutback’ by adding controlled amounts of petroleum distillates such as kerosene.

This is done 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 sprayed sealing with neat bitumen. The materials used to cutback bitumen will evaporate after application to leave the remaining material similar in hardness to the original bitumen.

Application

Priming and 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. The primer will be able to carry traffic for a short time (although this practice is uncommon) and help control dust. Generally, primers are applied at rates between 0.5 and 1.4 L/m2. Cutback bitumens suitable for priming are also used for tack coats, which are applied 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. 

Application Puma Cutback Products Australian Standard Guide Pavement Surface Type Suitability
Priming & Tack Coating Puma Bitumen AMC00 AMC00 Low Porosity Surfaces
Puma Bitumen AMC0 AMC0 Medium Porosity Surfaces
Puma Bitumen AMC1 AMC1 High Porosity Surfaces
Primer Sealing & Pre-mixing Puma Bitumen AMC2 AMC2 Low Porosity Surfaces
Puma Bitumen AMC3 AMC3 Medium Porosity Surfaces
Puma Bitumen AMC4 AMC4 High Porosity Surfaces
Puma Bitumen AMC5 AMC5  
Sealing Puma Bitumen AMC6 AMC6  
Puma Bitumen AMC7 AMC7  

Primer Sealing 

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.

Sprayed Sealing 

Cutback bitumens are used 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 is sprayed onto the primed pavement onto which aggregate is spread.

Specifications

Puma Bitumen cutbacks are manufactured to comply with the requirements of Australian Standard AS 2157 Cutback bitumen.