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Cover of Guide to Pavement Technology Part 4A: Granular Base and Subbase Materials
Guide to Pavement Technology Part 4A: Granular Base and Subbase Materials
  • Publication no: AGPT04A-26
  • ISBN: 978-1-923617-76-6
  • Published: 8 September 2026
  • Edition: 2.0

Austroads’ Guide to Pavement Technology Part 4A: Granular Base and Subbase Materials contains advice on the selection, testing and specification of crushed rock and naturally occurring granular materials for use in pavement base and subbase construction.

Edition 2.0 includes:

  • improved clarity and formatting
  • additional text related to recycled materials
  • editorial updates throughout the Guide.

Superseded editions:

Edition 1.2 published May 2024

Edition 1.1 published August 2018

Edition 1.0 published September 2008

  • 1. Introduction
    • 1.1 Scope
  • 2. Role and Function of Granular Materials in a Pavement
    • 2.1 Function of a road pavement
    • 2.2 Requirements of a pavement material
    • 2.3 Function of granular base and subbase materials
    • 2.4 Operating environment
  • 3. Behaviour of Granular Pavement Materials in Service
    • 3.1 Introduction
    • 3.2 Shear strength
      • 3.2.1 Particle shape and surface texture
      • 3.2.2 Fines content and plasticity
      • 3.2.3 Particle size distribution
      • 3.2.4 Density and moisture content
    • 3.3 Modulus
      • 3.3.1 Particle size and shape
      • 3.3.2 Particle roughness and shape
      • 3.3.3 Fines content and plasticity
      • 3.3.4 Particle size distribution
      • 3.3.5 Density and moisture content
    • 3.4 Permanent deformation
      • 3.4.1 Particle shape
      • 3.4.2 Particle size distribution
      • 3.4.3 Fines content
      • 3.4.4 Density and moisture content
    • 3.5 Durability
      • 3.6 Permeability
      • 3.6.1 Particle size distribution
      • 3.6.2 Fines content and plasticity
      • 3.6.3 Density and moisture content
    • 3.7 Compaction (density and moisture)
      • 3.7.1 Particle size distribution
      • 3.7.2 Maximum size
      • 3.7.3 Particle shape
      • 3.7.4 Fines content
  • 4. Production of Granular Materials
    • 4.1 Methods of granular material production
      • 4.1.1 Crushing plant operations
      • 4.1.2 Use of additives in production
    • 4.2 Production of naturally occurring granular materials
      • 4.2.1 General
      • 4.2.2 Methods of production
      • 4.2.3 Material assessment
    • 4.3 Production of crushed rock
      • 4.3.1 Methods of production
    • 4.4 Use of recycled materials
  • 5. Properties of Crushed Rock Requiring Specification
    • 5.1 Specification principles
    • 5.2 Specification types
    • 5.3 Source rock
    • 5.4 Key product requirements
      • 5.4.1 Introduction
      • 5.4.2 Maximum size
      • 5.4.3 Particle size distribution
      • 5.4.4 Particle shape
      • 5.4.5 Nature of fines
      • 5.4.6 Illustrative test limits for crushed rock
  • 6. Properties of Naturally Occurring Granular Materials Requiring Specification
    • 6.1 Use of natural occurring materials in granular pavements
    • 6.2 Particle size distribution
    • 6.3 Clay and silt content
    • 6.4 Particle shape and texture
    • 6.5 Maximum particle size
    • 6.6 Particle strength and durability
    • 6.7 Compacted density and moisture content
    • 6.8 Illustrative test limits for natural gravels
  • 7. Assessment and Testing of Granular Materials
    • 7.1 Overview of assessment methods
    • 7.2 Source rock tests for crushed rock
    • 7.3 Product tests
      • 7.3.1 Particle size distribution
      • 7.3.2 Particle shape
      • 7.3.3 Particle density and absorption
      • 7.3.4 Consistency limits
      • 7.3.5 Soil fines
      • 7.3.6 Contaminants
      • 7.3.7 Assessment of granular base and subbase materials containing recycled materials
      • 7.3.8 Unsound stone content
      • 7.3.9 California Bearing Ratio
      • 7.3.10 Repeated load triaxial test
      • 7.3.11 Wheel-tracking test
      • 7.3.12 Permeability
  • References
  • Appendix A Illustrative Test Limits for Crushed Rock
    • A.1 Quality System
    • A.2 Test methods
    • A.3 Materials
    • A.4 Source rock specifications
      • A.4.1 Coarse aggregate fraction (portion retained on a 4.75 mm AS sieve)
      • A.4.2 Wet strength and wet/dry strength variation
      • A.4.3 Los Angeles value and unsound and marginal stone content
      • A.4.4 Los Angeles value and sodium sulphate soundness loss
      • A.4.5 Fine fraction (portion passing a 4.75 mm AS sieve)
    • A.5 Product specifications
      • A.5.1 Sulphide mineralisation
      • A.5.2 Grading of crushed rock base and subbase
    • A.6 Moisture content
    • A.7 Stockpiling prior to delivery
    • A.8 Handling of materials
  • Appendix B Illustrative Test Limits for Natural Gravels
    • B.1 Particle size distribution
      • B.1.1 Gravel and soft rock
      • B.1.2 Sand-clays
    • B.2 Plastic limit
    • B.3 Liquid limit
    • B.4 Plasticity index
      • B.4.1 Gravel and soft rock
      • B.4.2 Sand-clays
      • B.4.3 Weighed plasticity index
    • B.5 Linear shrinkage
    • B.6 Maximum dry compressive strength
    • B.7 Miniature abrasion loss test
    • B.8 Ball mill value
    • B.9 Texas triaxial test
    • B.10 California Bearing Ratio test
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