Concrete MPa Grades Australia: 20 MPa, 25 MPa, 32 MPa, 40 MPa

What Is MPa in Concrete?

MPa stands for megapascals. In concrete, it measures compressive strength after 28 days. N20, N25, N32, and N40 are Australian normal-class grade names for 20, 25, 32, and 40 MPa concrete.

The letter and number answer different questions. In N32, the N is the normal-class label and 32 is the characteristic compressive strength: 32 MPa at 28 days. MPa is not a rival to the grade number; the MPa value is built into the grade name.

Strength and product type are still separate. N20 is normal-class 20 MPa concrete. BF20 or core-fill concrete can also be 20 MPa, but it is a flowable small-aggregate product for filling block cores rather than a standard N20 path or blinding mix.

Quick Reference: Australian Concrete Grades

The table below covers every standard grade you'll encounter on a residential or light commercial project in Sydney. Prices are delivered rates for March 2026. see Sydney delivery pricing for a breakdown of delivery fees and surcharges, or check national price guidance.

Source: Australian Standards AS 1379 and Cement Concrete & Aggregates Australia (CCAA).

Not Sure Which Grade? Use the Selector

Quick Answers: Driveway, Slab, Footings, Pool and Paths

If you already know the project type, use this as the starting point before checking engineering drawings or council requirements. The final order still needs the specified grade, slump, volume, and delivery access.

When to Use Each Grade

20 MPa (N20): Paths, Blinding, Light-Duty Slabs

20 MPa (N20) is the entry-level structural grade and the cheapest option at $320–340/m³ in Sydney. It's suitable for garden paths, concrete blinding under footings, and light-duty areas that won't carry vehicle loads.

Don't use 20 MPa where vehicles will drive. The lower compressive strength makes it prone to surface spalling and cracking under repeated car or ute loads. The saving over 25 MPa usually is not worth it for a driveway that needs to last 20+ years. See the full N20 concrete guide for suitable jobs, price, and ordering.

25 MPa (N25): Driveways, Residential Slabs, Garage Floors

25 MPa (N25) is the workhorse of residential concrete in Australia. According to CCAA data, 25 MPa concrete accounts for over 60% of residential ready-mix orders in Sydney. It provides the right balance of strength, durability, and cost for most suburban projects.

Use 25 MPa for: standard driveways, residential house slabs, garage floors, pergola footings, and most flat concrete work that will carry passenger vehicles. Most concreting contractors default to 25 MPa for residential work unless there's a specific reason to go higher or lower. The N25 concrete guide covers driveway and slab guidance, price, and live availability.

32 MPa (N32): Structural Slabs, Exposed Footings, Pools

32 MPa (N32) is required by AS 3600 for exposed footings and is the standard spec for structural slabs in Sydney residential construction. At $370–400/m³, it costs more than 25 MPa, with the exact uplift depending on plant, volume, delivery date, and postcode.

Use 32 MPa for: exposed footings (where ground movement or moisture is a factor), pool surrounds and structural pool walls, retaining walls, suspended slabs, and any slab that a structural engineer has specified in writing. When in doubt between 25 MPa and 32 MPa, the cost difference is often small enough that 32 MPa is worth the upgrade. The N32 concrete guide covers structural slab and footing use, exposure classes, and price.

40 MPa (N40): Commercial, Multi-Storey, High-Performance

40 MPa (N40) is a high-performance grade used in commercial and multi-storey residential construction. At $400–440/m³, it's rarely specified for standard residential projects. If your engineer has specified 40 MPa, you'll typically be working with a commercial concrete supplier who can confirm the mix design. The N40 concrete guide covers high-load structural use and price.

S-Class: Engineer-Specified for Structural Requirements

S-class (special class) concrete falls outside the standard N-grade system. It's used for bridges, industrial foundations, and structures with specific chemical resistance or load requirements. Always requires a structural engineer's specification. Price on application. Expect $350+/m³.

Australian Standards Reference

The two standards that govern concrete grades in Australia are:

• AS 1379: Specification and Supply of Concrete: Defines normal-class (N-grade) concrete. The grade number is the characteristic compressive strength in MPa at 28 days.
• AS 3600: Concrete Structures: Specifies minimum grade requirements for different structural applications. Requires 32 MPa (N32) for exposed footings and most structural elements.

The Building Code of Australia (BCA/NCC) requires a minimum of 20 MPa for residential concrete slabs. Most structural engineers in Sydney specify 25 MPa (N25) or higher for anything beyond blinding and paths, citing improved long-term durability in the coastal and sub-coastal climate.

When a concrete supplier asks for your "spec", they're asking for the grade, slump (workability), and sometimes the maximum aggregate size. For standard residential work, specifying "25 MPa (N25), 80mm slump" is sufficient.

Why Water Addition Destroys Your Concrete Grade

Adding water on-site is the fastest way to downgrade your concrete. The chart below shows the effect of water content on 28-day compressive strength — the same data that governs your N-grade specification.

Grade vs Price: Is Upgrading Worth It?

The decision rule is simple: if the driveway has heavy loads, exposure, or engineer risk, choose the higher MPa grade. For most Sydney residential projects under 6m³, the grade upgrade pays for itself in reduced maintenance and longer service life.

Need to calculate exactly how much concrete you need first? Use the MixHub calculator to get volume, grade recommendation, and a Sydney price estimate in one step.