When is it safe to walk on fresh concrete?

Usually after a day or two, depending on the conditions and the mix. Stay off the edges a little longer, since they gain strength last and chip most easily. If the pour wrapped up late in the afternoon, or a solid shower passed over while it was going off, allow the longer end of that range. We'll give you timings for your specific slab, so there's no guesswork.

When can I park on my new driveway?

Around a week for an ordinary car, as long as the slab was cured properly through those early days. It's tempting to jump in sooner, but a three- or four-day-old driveway is nowhere near its full strength, and tyres can scuff the surface or set off cracks that stay for good. For anything heavier, such as a caravan, a laden ute, a trailer or a delivery truck, hold off until it's closer to 28 days.

Why should new concrete be kept wet?

Concrete hardens through hydration, a chemical reaction between cement and water, rather than by drying. When the surface loses moisture too soon, the reaction stalls and the top layer never develops its full strength. So for the first several days we cover fresh slabs, mist them or apply a spray-on curing compound. Rapid drying, say on a hot, breezy summer afternoon or when a gusty southerly buster blows through, is also behind plastic shrinkage cracking and surface crazing.

How much does local weather affect curing?

A fair bit, and it varies through the year. Summer heat accelerates hydration, so the concrete stiffens sooner and the finishers have less time to work it, while a hot, windy day can dry the top before it has cured. For that reason we often pour early on summer mornings and may use a set retarder, an evaporation retarder sprayed on the surface and curing applied as soon as finishing is done. Chilly winter mornings work the other way: setting slows, finishing drags out and strength builds gradually, so we may tweak the mix and allow extra time before vehicles go on. Rain can turn up in any month here, and a heavy fall on unset concrete can wreck the finish, so we schedule pours around the forecast and keep covers ready.

Has concrete finished curing after 28 days?

Twenty-eight days is the accepted point at which concrete should hit its specified strength, and it's the figure engineers and the Australian Standards use. Strictly speaking, hydration continues at a diminishing pace for months or years, so the slab keeps gaining a little strength. For all practical purposes, though, after four weeks it's ready for whatever loads it was designed to take.

Concrete Curing Times: When Can You Use New Concrete?

The Short Version

Rough timings: walk on it after 24 to 48 hours, drive on it after about 7 days, and expect design strength at roughly 28 days.

Concrete doesn't get hard by drying out. Its strength comes from cement reacting chemically with water, so a slab that dries too soon finishes up weaker.

The weather can speed things up or slow them down. Locally, a hot, blustery summer's day can dry the top before it cures, a chilly winter morning delays the set, and a surprise downpour can scar a fresh finish.

What happens in the first few days counts most. Keep the new concrete moist, shaded and free of weight, because early treatment shapes how it performs for years.

Foot traffic after a day or two, cars after roughly a week and full strength at about four weeks. Those are the three usual milestones to keep in mind. Behind them sits a chemical process that's easy to disrupt while the concrete is young, and the harm is lasting, because a poorly cured slab never regains the strength it missed out on.

Locally, curing calls for more attention than those figures imply, since coastal weather can be tough on new concrete. Strong summer sun and wind can dry the surface prematurely, cold winter mornings drag everything out, and heavy rain can blow in from the sea or over the escarpment with little notice. Any of these can ruin a fresh slab, and jackhammering out a failed pour to start over is a costly lesson.

Typical curing times

Treat these as a rule of thumb, not a promise. They're based on a standard mix and proper curing, and in this climate proper curing is what keeps them accurate.

Stage	Timing	Safe to use for
Initial set	4 to 8 hours	Nothing at all. Keep right off it.
Foot traffic	24 to 48 hours	Gentle walking, well away from the edges.
Light use	3 to 4 days	Light objects only, with nothing dragged over it.
Vehicles	About 7 days	An ordinary car on the driveway.
Full design strength	Around 28 days	Trailers, heavier vehicles and normal use without special care.

At each stage, the edges and corners trail behind the centre of the slab. Being thinner, they shed heat and moisture quicker and are prone to chipping, so allow them a bit of extra time.

Curing and drying are different things

Concrete doesn't harden through drying. It hardens through hydration, where cement and water react to form the crystal structure that gives the slab its strength, and the reaction only carries on while water is available. When sun and wind draw moisture out too quickly, a slab can appear done yet be weaker, because hydration near the surface stopped prematurely. That's the reason we cover new concrete, keep it moist or spray on a curing membrane, and it's why a scorching, windy afternoon is far harsher on a pour than a still, early morning.

The payoff from proper curing

How a slab is cured has a major influence on its final strength, wear resistance and resistance to cracking. Concrete that's cured well copes with traffic, weather and spills for years, whereas poorly cured concrete dusts, crazes and begins to flake. Curing also sets the timetable for using it:

Walking: 24 to 48 hours, keeping off the edges for a little longer.
Cars: roughly 7 days.
Trailers and heavier vehicles: closer to 28 days.
Outdoor furniture on a new patio: wait several days, and watch out for thin-legged pieces that focus their weight on small points.

A three- or four-day-old slab is still well short of full strength, so putting load on it early risks marks or cracks that are there for good.

How local weather affects curing

Temperature governs the speed of hydration, and its influence is larger than most people assume. For our crew, that means early starts to get ahead of the heat, sheltering the slab from sun and wind, allowing for slower progress in winter, and keeping bookings flexible in case a heavy downpour lands on pour day. We'd sooner plan for that at the outset than commit to a date the weather won't cooperate with.

Mild and still: hydration progresses evenly. A gentle autumn or spring morning is about as good as it gets, though we still keep an eye on the sun as it climbs.
Hot, sunny and blustery: moisture leaves the surface quickly and crazing can result. The slab needs covering or constant moist curing, particularly under harsh summer sun or a dry westerly.
Chilly winter mornings: hydration slows down, setting takes longer and early strength comes on gradually. We may alter the mix, cover the slab overnight and allow more time before it takes a load.
Downpours and East Coast Lows: heavy rain on concrete that hasn't set can strip the finish and weaken the top layer. We time pours around the forecast and have covers ready.

Does slab thickness change curing?

To a degree. Thicker concrete retains moisture for longer, while thin edges and toppings lose it fast on hot, breezy days and are more prone to shrinkage cracking and crazing. The timings above remain a reasonable guide. What matters more is the weather, the concrete delivered and how well the surface is sheltered during the first 48 hours, since that window largely determines how the slab turns out. Our concrete slabs page covers thickness and site preparation in more depth.

Looking after fresh concrete

Caring for a new slab mainly comes down to holding moisture in and keeping loads off while it strengthens.

Hold the moisture in: plastic sheeting, regular misting or a curing membrane for roughly the first week.
Keep loads off: stay off the edges and avoid anything that concentrates heavy weight on one small area.
Shelter it: from direct sun, drying wind and heavy rain over the first day.
Rain before the set: this can pit the finish and leave a soft top layer. Once the surface has set, rain does no harm and can even assist curing.
No hosing: spraying a brand-new slab washes off surface paste and weakens the finish.
Hold off on sealing: moisture trapped under sealer turns it cloudy, and the only remedy is stripping and redoing it.

When to seal new concrete

Usually no earlier than about 28 days, and only when the surface is clean and thoroughly dry. Apply concrete sealer too soon and moisture gets locked in, producing a hazy finish that must be stripped and reapplied. Here that may mean holding out for a settled dry patch rather than sealing the day the slab turns four weeks old, because a humid, drizzly week, or a slab still damp from an East Coast Low, is the wrong moment to seal even fully cured concrete.

Questions about your pour?

Twenty-eight days is the benchmark engineers and the Australian Standards rely on, as that's when the slab ought to reach its specified strength. Hydration keeps creeping along for months and years after that. For day-to-day purposes, though, treat four weeks as the point where the slab can handle everything it was designed for. Get in touch and we'll set out timings that suit your project and the time of year you're pouring.