20 MPa concrete · N20 normal class
20 MPa Concrete: Uses, Specs & Ordering
20 MPa concrete describes strength first. N20 is normal-class 20 MPa concrete, while BF20 can also be 20 MPa but is a different block-fill product for core filling.
20 MPa concrete reaches a characteristic compressive strength of 20 MPa at 28 days. N20 is the normal-class version used for light-duty paths, blinding layers, garden edging, and non-structural pads. BF20/block fill can share the same strength number while using smaller aggregate and higher slump for block cores. Sydney 20 MPa material pricing is typically $320-340/m3 before delivery, short-load fees, pump hire, waiting time, and GST.
Reviewed by Ross Mildwater, Senior Advisor, Customer Operations at MixHub
Indicative material price
$320-340/m3
Sydney 2026 guide range. Delivery, short-load fees, pump hire, waiting time, and GST depend on postcode, date, volume, and access.
Common names
20 MPa (N20)
Suppliers, engineers, and plans may write this as 20 MPa, N20, or 20MPa. They all refer to the same normal-class concrete strength.
What does 20 MPa (N20) mean?
The letter and number answer different questions. In N20, N is the normal-class label and 20 is the characteristic compressive strength: 20 MPa at 28 days. The MPa value is built into the grade name, not competing with it.
Normal-class spec at a glance
| Compressive strength | 20 MPa at 28 days |
| Normal-class grade | N20 |
| Slump | Often 80-100 mm for standard supply; pump, block fill, or special-class mixes can differ. |
| Aggregate | Commonly 10, 14, or 20 mm depending on product, reinforcement, pumpability, and supplier range. |
| Standards context | AS 1379 supply/specification and AS 3600 design references where structural drawings nominate f'c. |
Strength is only one axis
A concrete order is better thought of as strength x class x slump x aggregate x product/application. The MPa number tells you strength. The prefix or product name tells you what kind of mix is being supplied.
Example order wording
N20 20 MPa normal-class concrete, 80 mm slump, 20 mm aggregate, delivered to site. For block cores, specify BF20/block fill or core fill with the supplier instead.
20 MPa vs N20 vs BF20
20 MPa on its own does not tell you the class or product. Strength, formal class, slump, aggregate, and application are separate axes. That is why N20 and BF20 can both be 20 MPa while being different mixes for different jobs.
| Label | Meaning | Example |
|---|---|---|
| 20 MPa | Strength axis only: characteristic compressive strength after 28 days. | A drawing or supplier quote may say 20 MPa before naming the class or product. |
| N20 | Normal-class 20 MPa concrete. N is the AS 1379 normal-class label. | General paths, blinding, garden edging, and light-duty pads where normal-class concrete is suitable. |
| S-class 20 MPa | Special-class concrete at 20 MPa where specific performance requirements are nominated. | A project-specific mix requiring durability, chloride resistance, early strength, shrinkage, or other performance controls. |
| BF20 / block fill | Commercial product/application label for block or core fill at 20 MPa, not an AS 1379 formal class. | Small-aggregate, high-slump flowable concrete pumped into hollow block cores. |
Where to use 20 MPa (N20) concrete
Use 20 MPa normal-class concrete for low-load work only. If the job needs flow into block cores, ask for block fill/core fill rather than assuming a standard N20 mix will work.
Garden paths
N20 can suit foot-traffic paths where vehicle loads and structural requirements are not involved.
Blinding layers
Use N20 for low-strength blinding or working layers when the drawings allow a normal-class 20 MPa mix.
Small pads
Light utility pads and mower strips may suit N20 when durability demands are low.
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Grade decisions: use, avoid, upgrade, or downgrade
Always follow the engineer's specification, approved drawings, council requirements, or builder direction where they nominate a concrete grade, slump, exposure class, reinforcement, or aggregate size.
When not to use 20 MPa (N20)
- Driveways, garage slabs, shared accessways, or vehicle traffic where N25 is usually the practical minimum.
- Engineer-specified slabs, footings, suspended slabs, pools, or retaining-wall work.
- Exposed or wet structural elements where durability and exposure class requirements can exceed 20 MPa.
| Decision | Recommendation | Why |
|---|---|---|
| Use N20 | Paths, garden edging, blinding layers, and small non-structural pads. | It keeps material cost down where loads and durability requirements are modest. |
| Upgrade to N25 | Driveways, garage slabs, paths that need extra durability, and most residential slabs. | The small price uplift usually buys a more durable mix for common residential work. |
| Upgrade to N32+ | Footings, pools, exposed structural work, heavy vehicles, or engineer-specified pours. | Higher load and exposure risk should follow the engineering specification, not a light-duty default. |
Plan the grade, volume, and delivery method together
N20 concrete FAQs
Is N20 concrete the same as 20 MPa?
Can I use N20 concrete for a driveway?
How much does N20 concrete cost?
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