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Optimising Pavement Structure with Recycled Materials

Understanding Pavement Structure and Materials

Pavement structures and the materials used can vary significantly based on subgrade strength and construction approach. Some projects opt for full-depth asphalt directly on the compacted subgrade, while others employ an aggregate base beneath the asphalt layers. Below, we provide illustrative minimum pavement designs, specifying the compacted layer thicknesses.

Full-Depth Asphalt Pavement (Table 1)

Optimising Pavement Structure with Recycled Materials

Asphalt with Aggregate Sub-Base Pavement (Table 2)

Optimising Pavement Structure with Recycled Materials

Notes on Material Specifications

  • Surface (SM-9.5): This specifies the asphalt mix type. For detailed specifications, refer to NZTA M10.
  • Base (IM-19.0 or BM-25.0): This indicates the asphalt mix type, with detailed specifications available in NZTA M10.
  • Aggregate Base (21B): Basecourse materials must comply with NZS 4407:2015, such as AP40 or AP65, ensuring proper compaction.
  • Subgrade Conditions: Use Dynamic Cone Penetrometer Bearing Ratio (DCBR) values to determine subgrade strength.

Material Specifications

  1. Asphalt Binders: Specified by NZTA M10 Part 2, including grades like medium, hard, and very hard paving grades.
  2. Aggregate Base Materials: Must comply with NZS 4407:2015 (e.g., AP40, AP65).

Consultation and Compliance

  • Consult with local pavement engineers, contractors, or NZTA representatives to ensure compliance with regional or project-specific requirements.
  • Refer to NZTA guidelines and standards for construction practices, compaction requirements, and material properties.

References

  • NZTA M10: Specifications for Asphalt Materials and Mix Designs.
  • NZS 4407:2015: Specifications for Aggregate Basecourse Materials.

Related Links

Schematic Elevation View of Pavement System

Recycled aggregate blends for backfilling deep trenches in trafficable areas offers a schematic elevation view of pavement systems over various materials:

Optimising Pavement Structure with Recycled Materials
  1. Surrounding Natural Subgrade:
    • Depicts the typical pavement structure over the natural subgrade, highlighting standard construction practices and material considerations.
  2. Conventional Backfill for Trafficable Areas:
    • Shows a conventional pavement structure over a trench backfilled with standard materials, serving as a baseline for comparison.
  3. Proposed Recycled Material Blends for Trafficable Areas:
    • Introduces innovative blends of recycled materials designed for trafficable areas, aiming to enhance sustainability while meeting or exceeding performance requirements.

Key Considerations for Recycled Concrete Aggregate (RCA) in Pavement Construction

CBR Requirements

Understanding CBR (California Bearing Ratio) values is crucial. While natural subgrades typically require a minimum CBR of 3, materials used for trench backfilling in trafficable areas often necessitate higher CBR values, such as 20, to ensure adequate strength and durability under traffic loads.

Material Feasibility

Evaluate the feasibility of using recycled material blends based on CBR testing and compliance with local standards (e.g., NZTA specifications).

Performance Benefits

Consider the potential benefits of using recycled materials, such as reduced environmental impact and resource conservation, alongside meeting or exceeding performance criteria.

Application in New Zealand

Compliance and Standards

Refer to local guidelines and standards, such as NZTA M10 and NZS 4407:2015, for specific requirements on material properties, mix designs, and construction practices involving RCA.

Consultation and Testing

Consult with local pavement engineers and conduct rigorous testing, including CBR testing, to ensure that recycled material blends meet regulatory and performance expectations for trafficable areas.

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