Crumb Rubber Spray Seals

A spray seal is a widely used road surfacing technique in Australia, involving the application of a thin layer of bituminous binder onto a prepared pavement surface, followed by the spreading of aggregate. This method creates a waterproof, skid-resistant surface suitable for various traffic conditions.

Incorporating crumb rubber from end-of-life tyres into the binder enhances the flexibility and durability of spray seals. Crumb Rubber Modified Binders (CRMB) have been utilised in Australia for several decades to improve the performance of sprayed seals. The Austroads National Specification for Crumb Rubber Binders in Asphalt and Seals (AP-T359-21) provides guidance on the use of CRMB in sprayed sealing applications. 

Key Benefits of CRMB in Spray Seals:

• Enhanced Flexibility: Improves resistance to cracking under thermal stress and heavy traffic loads.
• Increased Durability: Extends the lifespan of the seal, reducing maintenance requirements.
• Environmental Sustainability: Utilises recycled tyre rubber, supporting circular economy initiatives.
• Improved Performance: Offers better adhesion and cohesion properties, leading to a more robust seal.

Application Process:

1. Surface Preparation: The existing pavement is cleaned and prepared to ensure proper adhesion.
2. Binder Application: A hot mixture of bitumen and crumb rubber is sprayed onto the surface using specialized equipment.
3. Aggregate Spreading: A layer of aggregate (typically 7mm, 10mm, or 14mm in size) is spread over the binder.
4. Compaction: The aggregate is embedded into the binder using rollers, creating a uniform and skid-resistant surface.

Specifications and Guidelines:

For detailed information on the use of crumb rubber in spray seals, refer to the following resources:

• Austroads National Specification for Crumb Rubber Binders in Asphalt and Seals (AP-T359-21): Provides comprehensive guidelines on the formulation and application of CRMB in spray seals.
• Guide to Pavement Technology Part 4K: Selection and Design of Sprayed Seals: Offers insights into the design and selection process for sprayed seals, including considerations for modified binders.