How Long Before You Can Walk and Drive on New Concrete

Walk on it after about 24 to 48 hours. Keep vehicles off for at least seven days. Wait a month before anything heavy. Concrete keeps gaining strength for weeks after it stops looking wet, and most of the damage I get called back to look at happens in that first week.

This is the question I get on every job, usually about ten minutes after we've put the finish on. So here it is properly.

Curing is not drying

This is the bit almost nobody is told, and it changes how you treat a new slab.

Concrete doesn't harden by drying out. It hardens by a chemical reaction between the cement and the water, and that reaction needs the water to stay in there. If a slab dries out too fast in the first few days, the reaction stops early and you end up with a weaker, dustier surface that is more likely to craze and crack.

So on a hot or windy day, keeping the surface damp is genuinely helping it. It feels backwards. It isn't.

A Gippsland winter pour takes longer

Cold slows the reaction down. A slab poured in July in Sale will not be at the same strength on day seven as the same slab poured in January. If we pour in the cold months I'll tell you on the day whether to stretch the timings, and it's usually worth adding a few days before you drive on it.

Frost on a fresh pour is the one to actually worry about, which is why we watch the forecast and sometimes move a date rather than push through.

What actually damages a young slab

It's rarely the weight. It's these:

• Turning the steering wheel while the car is stationary. That grinds the surface and it will leave scuff marks you can't get out. Roll forward as you turn instead
• Parking a loaded trailer on it, especially with the jockey wheel down. All that weight goes through one small point
• Driving on the edges. Edges and corners are the weakest part of any slab and the first thing to break away
• A skip bin or a delivery truck in week one. This is the most common one, and it usually happens because nobody thought to mention the new concrete to the driver
• Pressure washing it too early. Give it a month before it sees a pressure washer
• Salt or de-icer. Not much of a Gippsland problem, but worth knowing if you buy anything for a frosty morning

If you've got a build going on, tell the other trades. A new driveway and a bricky's truck in the same week is a conversation I've had more than once.

What you can do to help it

• In hot weather, keep it damp for the first few days. A light spray morning and evening is plenty
• Leave any curing compound or cover we've put on alone until we say otherwise
• Stay off the edges for the first week even on foot
• Don't cover it with anything that traps and stains, like a tarp with dirt under it

When to seal it

Not straight away. A slab wants time before it takes a sealer, generally around a month, and on some finishes longer. Sealing too early traps moisture and can leave the surface cloudy.

Whether you seal at all depends on the finish. Exposed aggregate and decorative work usually benefit. A plain broom finish driveway often doesn't need it. I'll tell you which one you've got and roughly when to look at it again.

Hairline cracks in the first few weeks

Some fine cracking is normal and is not a fault. Concrete shrinks slightly as it cures, which is exactly why we put control joints in: they give it a planned place to crack rather than a random one. If a crack follows a joint, that's the joint doing its job.

If you see something that worries you, ring me and send a photo. I'd rather look at it than have you wondering. There's more on this in our piece on whether your concrete will crack.

Any doubt, just ask

You'll have my number for the whole job and after it. If you're not sure whether something is safe to put on your new slab yet, ring me on +61 400 345 453 before you do it rather than after.