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#22-01 New asphaltic surfacing material and density testing specifications

Published: | Category: Technical advice note | Audiences: Road controlling authorities, Road traffic engineers & consultants, Roading contractors

This note is to advise that there are two new specifications added to the roading toolbox.  The M32 asphalt specification sets out requirements for EME 2 High Modulus Asphalt, and the T23 density test method specification sets out a methodology for determining the density of pavement layers that can be used alongside existing methods. 

Publication details

  • Author:
  • Published: 1 March 2022
  • Reference: 22-01
  • Contact: pavements@nzta.govt.nz

Purpose

This note is to advise that there are two new specifications added to the roading toolbox. The M32 asphalt specification sets out requirements for EME 2 High Modulus Asphalt, and the T23 density test method specification sets out a methodology for determining the density of pavement layers that can be used alongside existing methods. The new specifications may be used as appropriate from the date of this notice.

General information

M32 Asphalt Specification

This materials specification provides a standard approach to the provision of EME 2 High Modulus Asphalt in New Zealand. This product was developed in France and is now used in many parts of the world, including Australian jurisdictions. It offers a good option for pavement designers for severe applications where high temperatures, long loading times and many loading cycles are experienced and more conventional materials may experience reduced lives.

This new M32 specification has been developed by a cross-industry working group to provide a basis for the use of EME 2 High Modulus Asphalt in heavy duty pavements. EME 2 has been shown to provide very good deformation resistance while maintaining a long fatigue life in pavements.

T23 Density Test Method

The new T23 density test method provides a procedure for determining the density of modified, bound and unbound granular pavements by using a nuclear densometer in direct transmission mode. This mode allows determination of the average density at various depths and, by calculation, estimating the density of surface and sub-surface layers. The test method provides a means for determining the vertical uniformity of compaction and hence density in the pavement layer.

This test method is particularly applicable to modified pavements that have been laid in one layer and in-situ stabilised in accordance with NZTA B05 specification.

Reason for the change

M32 Asphalt Specification

EME 2 has been used in projects in New Zealand prior to the development of M32 but the absence of a technical specification has hindered its appropriate use. Publication of M32 will allow the appropriate use of EME 2 High Modulus Asphalt for State Highway, and other applications such as local authority roads and heavy-duty industrial pavements.

T23 Density Test Method

The new density test method is not intended as a replacement for routine density testing using the method of NZS 4407 Test 4.3 (i.e. nuclear density meter in backscatter mode) but should be used in parallel to test 4.3 to investigate the vertical uniformity of pavement layers. The aim of this test is to measure the uniformity of layer compaction and ensure that construction does not leave weak areas in the pavement that can lead to early failure.

Communication plan

Technical specifications such as these are only useful if they can be introduced as possible tools as widely as can be achieved. To that end, our communications will mostly be focussed externally. Advice of these changes will be promulgated by:

  • this note advising the release of the two specifications
  • via appropriate industry organisations
  • direct access via the website and intranet
  • delivery of presentations at appropriate fora later in the year.

Implementation

The main aim of implementation is make people in the industry aware that there are two new tools available for their use. There is no intent to push any barrows as it is realised that their use may involve extra costs. Therefore the main aspect of the implementation of these specifications is as a communications exercise so that potential users can make their own choices.

The purpose is one of awareness so that the specifications can be accessed and users can make their own assessment.

Document review

A review of the effectiveness of the changes will be undertaken in June 2023.

Publication details

Author: Waka Kotahi NZ Transport Agency
Published: February 2022
Version: 1
Location:
M32 High modulus asphalt (EME 2)

T23 Estimation of the density of compacted aggregate layers by direct transmission

Further information

If you have any questions or feedback, please contact the Principal Surfacings Engineer at pavements@nzta.govt.nz

 

Signed:


Greg Haldane
Chair, Ratification Group

Vanessa Browne
Delegated Approver