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The NZTA T24:2025, Determination of the Plateau Dry Density for Pavement Layers, was developed through a four-year collaboration between NZTA, contractors and IANZ-accredited laboratories.

The T24 Test is designed to determine the maximum in-field dry density for granular pavement layers, ensuring that compaction meets or exceeds laboratory Maximum Dry Density (MDD-Lab) standards and involves a collaborative approach, where contractors oversee construction while accredited labs conduct the sampling and testing.

The process includes defined compaction stages, primary, secondary, and final, each carefully measured through vigorous testing and validation. Test validity is established through visual inspections and density checks, with the final results signed off by the relevant authority. The test procedure was refined based on real-world results and comprehensive consultation, culminating in final approval and publication in August 2025. The test’s implementation and monitoring are embedded in the long-term IDM contract.

NZTA would like to thank the contributors, which included Higgins, Downer, Fulton Hogan, Hiways, WSP laboratories, NPTG and CETANZ who played pivotal roles in drafting documents, managing feedback, and guiding the approval process.

While the development of this test has been robustly developed, ongoing stakeholder engagement and regular specification reviews are planned to ensure continued relevance and effectiveness. NZTA therefore requests that any comments or suggestions for improvement be forwarded to pavements@nzta.govt.nz

Short URL to this page:
www.nzta.govt.nz/plateau-density-test