Back in August the new M03 Sub-base (2025) specification and notes were introduced for public use, replacing the old Sub-base notes from 1986, explains Mike Chilton, the AQA Technical Adviser.
The new specification and notes were developed by a joint working group representing the NZTA, the quarrying industry, CCNZ, industry consultants and CETANZ (civil engineering testing professionals) over three years.
Four members of the AQA Technical Committee were involved in the development of the specification.
The 1986 Notes document resulted in many different sub-base specifications around the country, often in the same geographical area. This meant quarries were holding and testing similar, but different, materials in stockpiles, often using overly premium feedstock.
The new specification is intended to reduce the variation in sub-base aggregate and simplify stockpiling and production at the quarry, while maintaining a suitable standard for state highway use.
The 2025 specification continues with the idea of classes of aggregate, similar to the M04 2024 basecourse specification. Class 5 sub-base is intended for use under Classes 1 and 2 basecourse and Class 6 sub-base is for use under Classes 3 and 4 basecourse.
Something new with this specification is that a quarry may nominate its own particle size distribution (PSD) when this is combined with acceptable repeated load triaxial (RLT) testing and permeability. This gives quarries, which may not easily meet the PSD limits, the ability to produce suitable sub-base without unnecessary scalping/wastage.
Recycled crushed concrete is encouraged, with either a 40mm or 65mm top size acceptable as sub-base and limits placed on foreign materials.
A summary of the required aggregate testing is displayed in this table below.
Time for your production results
The NZPAM’s annual production survey for 2024 is now closed, but I encourage you to do a late response if you haven’t already done so.
As Infometrics economist Brad Olsen reminded our industry at the QuarryNZ conference this year, the failure of a high percentage of quarries to report production is counting against us. Fewer than 40 per cent of our 1000 commercial quarries have reported aggregate production in some recent years.
As Brad reminded us, without your input it’s really hard to make our case to government with data that can be out by tens of millions of tonnes.
So please, take a few minutes answering the survey; it could make your lives a whole lot easier. You have three options but NZPAM recommends the online response. https://www.nzpam.govt.nz/nz-industry/nz-minerals/minerals-statistics/annual-return-of-industrial-rocks-and-minerals-output-2024
If you need any help or advice in filling in your survey, you are welcome to contact me.
tech@aqa.org.nz
Why I look forward to greener generation