By the ConConnect team · Updated August 2026 · Definitions per Cement Australia, Boral and AS 3972
Cement is an ingredient of concrete — the fine grey powder that binds everything together, making up just 10–15% of the mix by volume. Concrete is the finished material: cement plus sand, coarse aggregate and water. So the driveway is concrete, the truck is a concrete agitator, and the only thing that's actually cement is the bag of powder. Here's the whole family — and which bag to buy for your job.
They're all the same base chemistry — cement plus water — with different fillers for different jobs. What changes is the aggregate: coarse stone makes concrete structural, straight sand keeps mortar and render workable.
| Material | What's in it | What it's for |
|---|---|---|
| Cement | Fine grey powder — limestone and clay fired to clinker, ground with gypsum | The binder in everything below; never used alone structurally |
| Concrete | Cement + sand + coarse aggregate + water | Slabs, driveways, footings, posts — anything structural |
| Mortar | Cement + sand + lime (no coarse aggregate) | Bedding and jointing brickwork and blockwork |
| Render | Cement + lime + fine sand | Coating walls for finish and weather protection |
| Grout | Flowable cement-based mix | Filling gaps, voids and tile joints |
| Screed | Cement + sharp sand (roughly 1:3 to 1:5) | Levelling layer over a slab before tiles or timber |
Why can't you just build with cement? Because cement paste on its own shrinks as it dries, cracks, and wears quickly. The aggregate isn't filler — it's a rigid skeleton that restrains shrinkage and carries the load, which is why the mix ratio matters so much.
The bags sit side by side at the hardware store and cost within a couple of dollars of each other — buying the wrong one is the classic weekend mistake. Hardware store prices at the time of writing:
| Bag | Typical price |
|---|---|
| General purpose cement (20kg) | $8.82 |
| Pre-mixed concrete (20kg) | $8.69 |
| Mortar mix (20kg) | $10.59 |
Grab pre-mixed concrete bags — sand, cement and stone already blended, just add water. About 110 × 20kg bags make a cubic metre; work out how many you need. Rapid-set versions are for fence posts only — not load-bearing posts like pergolas.
Buy straight cement only if you're mixing it with sand and aggregate yourself — cheaper per m³ on bigger hand-mixed jobs, but you own the ratios. Past about half a cube, ordered ready-mix beats both options.
Mortar mix is the bag for brickwork, blockwork and paving joints — cement and sand with the right additives, no stone. Don't substitute concrete mix; the aggregate makes it unusable in a brick joint.
Australian bagged and bulk cement is made to AS 3972, and the letters on the bag mean something. Type GP (general purpose) is the default — Portland cement clinker ground with gypsum, allowed up to 7.5% limestone. Type GB (blended) swaps in fly ash or slag — slightly slower early strength, better long-term durability, and what "builders cement" bags usually are. Type GL carries 8–20% limestone for lower embodied carbon.
Special-purpose types exist for engineered work — HE (high early strength), LH (low heat), SR (sulfate resisting) and SL (shrinkage limited) — but for residential concrete you'll almost always be using GP or GB, and for ready-mix you specify strength in MPa and let the batch plant pick the cement. Once it's poured, the clock starts — here's how long concrete takes to cure.
Cement is an ingredient of concrete, not the same thing. Cement is the fine grey powder that binds; concrete is the finished building material — cement (10–15% by volume) mixed with sand, coarse aggregate and water. So a driveway, slab or footpath is concrete; the powder in the bag is cement.
For anything you build — slabs, paths, footings, fence posts — you want concrete. Cement on its own is only used as an ingredient: for mixing your own concrete, making mortar or render, or as a bonding agent in small repairs. For small DIY jobs, a bag of pre-mixed concrete is simpler than batching cement, sand and aggregate yourself.
Neither, strictly — they use mortar: cement mixed with sand and usually lime, with no coarse aggregate. Mortar stays workable and sticky so it beds and joints bricks and blocks, which is a different job to the structural strength concrete provides. A common Australian mortar mix is 1 part cement, 1 part lime, 6 parts sand.
No. Pure cement paste shrinks as it dries, cracks easily and wears poorly, which is why nothing structural is built from cement alone. The sand and coarse aggregate in concrete form a rigid skeleton that restrains shrinkage and carries load — the aggregate is structural, not filler.
It's a long-standing misnomer that stuck — people say 'cement driveway' or 'cement truck' when the material is concrete. The industry line is blunt: there's no such thing as a cement driveway or a cement mixer, because cement is only the powdered binder. The habit is common in Australia too; concreters will know what you mean, but the correct word is concrete.
Cement and sand without coarse aggregate isn't concrete — it's a sand-cement mix, which is what mortar and screeds are made from. It's right for bedding pavers, levelling floors and bricklaying, but it lacks the aggregate skeleton that gives concrete its strength, so don't use it for slabs, driveways or footings.
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