How long does concrete take to dry?

Rapid Set hardens in about 15 minutes at 20°C (68°F) and, by the usual rule of thumb, about 8 minutes at 30°C (86°F), but every concrete keeps curing for days: Cement Australia says keep it damp for 7 days.

1. What are you doing?

2. Shape

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3. Your job

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4. Sizes

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Width (m)

Depth (mm)

Sloped (deeper at one end)

Product

Extra allowed (%)

Allmat concrete calculator

What we'd use

Concrete Mix 20kg: 104 bags

Allow an equivalent brand to specification

You need 0.95 m³ of concrete

0.9 m³ plus extra for spillage and uneven ground (5% on the slab or pad).

Or order a ready-mix truck: ask for about 1 m³.

Details: other bag sizes, water, weight, getting it home

About 104 x 20kg or 84 x 25kg bags of concrete, our estimate from bag weight.

Concrete Mix 20kg (104 × 20 kg): Water: about 182 L. Weight: 2,080kg. Mixer loads at 2 bags a load: 52.

That adds 10% and rounds up to the next step a supplier sells.

Cement Australia's guide: under 0.1 m³ use bags, 0.1 to 0.5 m³ mix your own, over 0.5 m³ ready-mix. Up to about 1 m³ we still show the bags; past that, and for a house slab or a driveway beyond a small patch, it is a truck pour.

Getting it home

Total weight: 2,080kg. About 3 ute loads at 1,000kg each, our estimate.

The load alone is over 750kg, the limit for an unbraked trailer, and the trailer's own weight counts too.

Click and collect or delivered across Adelaide.

How we worked it out

Slab or pad: 0.9 m³ plus 5% = 0.95 m³, ordered as ready-mix.

Cement Australia: about 110 x 20kg bags make 1 m³ (their FAQ, calculator and the PROSTRENGTH Rapid Set data sheet). Rapid Set Concrete publishes no per-m³ figure, so it uses the same 110.

Trade Mortar: about 20 house bricks or 10 masonry blocks per 20kg bag at a 10mm joint (Cement Australia).

Estimates only. Check sizes and quantities against your plans, and with your engineer or builder, before you order.

Pour-day check

Type in the weather for the day you plan to pour. Temperature never changes how much you need; it changes the timing.

Air temp (°C)

Wind (km/h)

Humidity (%)

Concrete Mix 20kg: 20°C is within the maker's range (5°C to 35°C).
Ready-mix (house slab or driveway): AS 1379 requires the concrete to arrive between 5°C and 35°C; outside that, talk to the plant (CCAA).
Keep it damp for 7 days (Cement Australia).

Set, dry and cure are three different things

Concrete sets when it stops being workable, which takes minutes for rapid set products and hours for a standard mix. It feels dry on top within a day. It cures, gaining strength, for weeks, and the first week matters most.

Cement Australia's times for Concrete Mix: formwork can come off after 24 hours, keep off it for at least 3 days, and avoid heavy loads for at least 7 days.

How temperature changes concrete curing time

Warmth speeds concrete up and cold slows it down. A rule of thumb is that set time halves for every 10°C warmer and doubles for every 10°C colder.

Minutes for rapid set concrete to harden, by air temperature (guidance)
Product	10°C	15°C	20°C	25°C	30°C	35°C
Rapid Set Concrete	30	21	15	11	8	5
PROSTRENGTH Rapid Set	60	42	30	21	15	11

Starting from Cement Australia's stated times (about 15 and 30 minutes), halving for each 10°C warmer and doubling for each 10°C colder: a rule of thumb, not a maker's figure. "Not advised" is outside the maker's temperature range.

Pouring concrete in cold weather, heat or rain

Cold: Cement Australia gives 5°C (41°F) as the lowest temperature for Concrete Mix and 10°C (50°F) for Rapid Set. Below that, wait for a warmer day.
Heat: Cement Australia says not to mix or place concrete above 35°C (95°F), so postpone to a cooler day. On warm days within that limit, work early and keep the surface damp.
Rain (general practice, not a maker's figure): cover fresh concrete, because rain on a surface that is not finished can weaken it.

Questions

Cement Australia says to keep off Concrete Mix for at least 3 days. PROSTRENGTH Extra Strength can usually be walked on the next day.

As general practice, wait for a dry day, and keep a cover handy in case a shower comes. Rain on fresh concrete weakens the surface.

Keep it damp for 7 days, which is when most of the strength develops. It keeps gaining strength for weeks after that.

Yes. As a rough guide, set time doubles for every 10°C colder, and under 5°C fresh concrete needs protecting.

Goes with this job

Disclaimer

This calculator gives estimates from the sizes you enter, using manufacturers' published figures and standard geometry. It is not engineering or design advice. Footing, slab and beam sizes must come from your plans or engineer. Allow for site conditions, spillage and uneven ground. Check quantities with your supplier before ordering. Allmat accepts no responsibility for decisions made using these estimates.

Sources

Last checked 5 October 2026.

Cite this page

Allmat, "How long does concrete take to dry?", https://allmat.com.au/concrete-calculator/drying-time, checked 5 October 2026.