Published: 7 October 2021 | Category: Technical advice note | Audiences: Road traffic engineers & consultants, Roading contractors
Waka Kotahi NZ Transport Agency wishes to advise that Specification P23: 2005 performance-based specification for hotmix asphalt wearing course surfacing, and its accompanying Notes, have been withdrawn and must no longer be used in new Waka Kotahi contracts. This change will be active from the date of publication of this notice.
Waka Kotahi NZ Transport Agency wishes to advise that Specification P23: 2005 Performance-Based Specification for Hotmix Asphalt Wearing Course Surfacing, and its accompanying Notes, have been withdrawn and must no longer be used in new Waka Kotahi contracts. This change will be active from the date of publication of this notice.
P23 specification was developed in 2005 to encourage innovation in thin asphalt wearing courses. It was developed in the context of empirical method specifications for dense asphalts (M10: 2002), open-graded porous asphalts (P11: 2003) and stone mastic asphalt (BCA 9808). P23 was intended only for use with “the permission of the manager of Transit’s Engineering Policy Section as it is still under development” (P23 Notes). It has had no further development since 2005.
Since 2005 advances in asphalt technologies and the availability of sophisticated performance-related design and testing services in New Zealand laboratories have resulted in upgrades to NZTA asphalt material specifications (M10: 2020, M27: 2020, P11: 2007). These upgrades have superseded P23 and it is now appropriate for P23 to be withdrawn.
The withdrawal of P23 has been unanimously endorsed by the National Surfacings Technical Group (04 May 21). The standard approach in future contracts will be managed under the appropriate NZTA asphalt surfacing specification; M10 for dense asphalts, M27 for stone mastic asphalt or P11 for open-graded asphalts.
However, Waka Kotahi does not want to rule out instances where an innovative or proprietary asphalt surfacing is proposed as an appropriate solution by a contractor or other industry representative. Advice and guidance from the Waka Kotahi Principal Surfacings Engineer should be sought. If necessary, this may be approved by the Lead Advisor Pavements as a departure from the contract specification.
If you have any questions or feedback, please contact the Lead Adviser Pavements, Adam Leslie at pavements@nzta.govt.nz
Signed:
Greg Haldane
Chair, Ratification Group
Vanessa Browne
Delegated Approver
