Cutback bitumen is used in spray sealing applications where traditional bitumen is too viscous to apply directly or where surface preparation is critical. It is most commonly applied in three ways:

🔹 Priming (Prime Seal)

Used to penetrate and waterproof unsealed granular pavements before sealing. A low-viscosity cutback (like AMC00 or AMC1) is sprayed to create a bond between the basecourse and the future seal layer. It prepares the surface by stabilising dust, reducing absorption, and ensuring better adhesion of subsequent bitumen.

🔹 Primer Sealing (Primer Seal)

A one-pass treatment that combines a cutback bitumen (usually AMC2 to AMC4) with a single application of aggregate. It acts as a temporary wearing surface, typically on light-traffic roads or as an interim seal before a final seal is applied. Primer seals are often used in remote areas or staged construction.

🔹 Spray Sealing with Cutter (Light Cutback Addition)

In cooler temperatures or when working with aged surfaces, a small proportion of cutter (kerosene or light oil) may be added to standard bitumen to improve sprayability and adhesion. This reduces the binder’s initial viscosity and ensures better wetting and stone retention under marginal conditions.