AS 1379: specification and supply of concrete
AS 1379 is the standard for ordering and supplying concrete: normal-class grades N20 to N50, slump, aggregate, and what the delivery docket must show.
Ask Chalkline about this →AS 1379 is the Australian Standard that governs how concrete is specified, ordered, batched, supplied, sampled, and accepted from a premix supplier. The current edition is AS 1379-2007, Specification and supply of concrete (verified 2026-05-25). It is the standard the delivery docket on every concrete truck is written against, and it is called up by AS 3600 (concrete structures) and the NCC for structural concrete.
It draws the line between what the supplier is responsible for (the concrete as delivered) and what the builder and placer are responsible for (placing, compacting, finishing, and curing it on site).
Two categories: Normal class and Special class
AS 1379 splits concrete into two categories:
- Normal class (N): standard, off-the-shelf grades produced to set strength designations. Most residential slabs and footings are normal-class.
- Special class (S): anything specified to performance requirements beyond the normal range, exposure-classified concrete, high early strength, low-shrinkage, or strengths above N50. The engineer nominates special-class when the job needs it.
Normal-class strength grades
Normal-class grades run N20, N25, N32, N40, and N50. The number is the characteristic compressive strength in MPa at 28 days (so N32 is 32 MPa). For more on what the grade means, see concrete grade.
| Grade | Characteristic strength (28 days) | Typical residential use |
|---|---|---|
| N20 | 20 MPa | Non-structural, blinding, fill |
| N25 | 25 MPa | Footings, some slabs |
| N32 | 32 MPa | The common slab and footing grade |
| N40 | 40 MPa | Higher-load or exposure work |
| N50 | 50 MPa | Special applications |
The engineer’s specification sets the grade. Do not substitute down to save money; the grade is a structural decision.
Specifying normal-class concrete: the four things
When you order normal-class concrete, AS 1379 requires four things to be nominated:
- Strength grade (N20 to N50).
- Slump at the point of acceptance, in 10mm steps from 20mm to 120mm (a measure of workability, not water content to be topped up on site).
- Maximum nominal aggregate size, 10mm, 14mm, or 20mm.
- Intended method of placement (pump, chute, wheelbarrow, etc.), so the mix suits how it is going in.
Get any of these wrong on the order and the concrete that turns up may be unworkable or non-compliant for the job.
The delivery docket
Every load arrives with a delivery docket written against AS 1379. It records the supplier, the batch plant, the date and time batched, the specified grade, slump, maximum aggregate size, and the volume. The docket is your proof of what was actually supplied.
Check the docket against the engineer’s specification before the truck discharges. Confirm the grade, slump, and aggregate match the spec, and note the batch time, because the clock on placing and finishing starts then. A docket that does not match the spec is your one chance to reject the load before it is on the ground.
Sampling and acceptance
AS 1379 sets out how compliance is assessed, by sampling fresh concrete (slump and test cylinders) and testing the cylinders for compressive strength at 28 days. On larger or engineered jobs the engineer may require sampling to one of the standard’s assessment methods. The slump test at the point of acceptance is the quick on-site check; the cylinder results are the formal record.
For a builder
- The docket is the contract. Read it before discharge; match grade, slump, and aggregate to the spec, and keep it. It is your evidence if strength is later questioned.
- Do not add water on site. Adding water to restore slump increases the water-cement ratio and drops strength, putting the load outside what AS 1379 certified. If it is too stiff, that is a supply or timing issue, not a hose issue.
- Watch the clock. Time from batching is on the docket; placing and finishing have to happen inside the workable window, especially in heat.
- Grade is the engineer’s call. N32 is the common residential grade, but use what the structural drawings specify.
Also known as: AS 1379-2007, AS 1379 concrete standard.
Related
See also
Last updated: 2026-05-25. Verified: 2026-05-25. Quarterly review for currency.