Over the past decade in New Zealand there has been no calcined bauxite specification, leading to variable performance of calcined bauxite surfacings and in some cases very poor value for money.
Calcined bauxite is a specialised road surfacing that provides higher skid resistance than offered by a natural aggregate, such as greywacke or basalt. The benefits of having a specification and therefore a standard approach are certainty of documentation for contractors and improved performance for clients. This in turn should lead to longer life of calcined bauxite surfacings and better value for money.
Until now calcined bauxite has often required repair or replacement within two years. However, a properly installed calcined bauxite surfacing should achieve at least a six- to eight-year life.
The new specification provides realistic performance targets, which if achieved within the two-year Defects Liability Period, should ensure the expected life.
Calcined bauxite installation prices remain high at $40 to $60/m2 (especially when compared with other surface treatments at between $7.50 and $25.00/m2). With the current NZTA skid resistance policy, calcined bauxite will continue to only be required on a small percentage of the network. Calcined bauxite is usually used on approaches to critical intersections or very high stress curves with higher crash rates. Nevertheless, the cost difference still makes it essential that it is done correctly.
Trial and consultation
‘Pilot specification’ means that the P25 Specification can be used in trials. Feedback from these trials will be incorporated into a revised P25 next year. The period of P25 trial and consultation is from February 2012 to April 2013. You can submit comments and feedback at any time during this period using the feedback form below, or directly to the following email address firstname.lastname@example.org.
Pilot specification and notes
- Feedback form (Word, 188 KB)
- P25 Pilot Specification for Calcined Bauxite – Questions and Answers (PDF, 52 KB, 2 pages)