How Long Does Concrete Take to Cure? Setting, Moist Curing and the 28-Day Mark

How long concrete takes to cure depends on which stage you mean: it sets within hours, should be kept moist for at least 7 days, and its strength is judged at 28 days. Curing is the part you control: keeping the new slab wet and warm enough that the cement keeps reacting with water and gaining strength.

Setting, drying and curing are different things

Setting is the mix stiffening from a plastic mass into a solid. Ohio DOT’s 2013 specification for structural concrete, quoted throughout this guide, notes that initial set is generally within 6 hours of batching. Once it’s set you can’t rework it, but it’s far from full strength.

Curing is what happens next. The American Concrete Institute defines it as keeping moisture and temperature in the concrete so the cement keeps hydrating. Strength gain needs relative humidity above 80 percent inside the concrete and temperatures above 50°F.

Drying is the opposite of what young concrete needs. ACI says there’s no measure of curing itself, only of results like in-place strength, and that poor early curing frequently causes plastic shrinkage cracking and a weak, badly cracked surface.

Concrete curing timeline

When	What’s happening	What to do
First hours	The mix stiffens and reaches initial set	Finish it, then start curing as soon as the surface can take it
Days 1 and 2	Hardening; Ohio DOT allows at least 36 hours, or until strength tests reach 85 percent of the design strength, before work goes on over new concrete	Keep it wet or covered; keep loads off
Days 1 to 7	Hydration builds strength while moisture and warmth hold	Keep it wet, under plastic or under curing compound
Day 7	End of the wet cure in Ohio DOT’s spec	Coverings can come off in mild weather
Day 28	The age at which concrete strength is specified	This is the strength the mix was ordered for
After that	Strength can keep rising while it stays moist and above 50°F	Seal only once it’s cured and dry

Foot traffic, cars and trucks each have their own wait; our guide to how long before you can drive on new concrete covers those.

The 28-day mark is a testing convention. The IRC’s minimum strength table for foundations, porches, steps and garage slabs gives every value at 28 days. For what a finished slab can carry, see our article on how much weight a concrete driveway can hold.

Related: how thick a concrete driveway should be to carry cars and trucks

How long to keep concrete wet

Plan on 7 days. Ohio DOT’s water-curing method keeps two layers of wet burlap on new concrete for at least 7 days, and requires exposed faces to be cured if forms come off before then.

Stretch it when it’s cool. ACI says that between 40 and 60°F, moist curing should be prolonged, and below 40°F hydration is greatly retarded. A slab poured in a mild week of late fall gains very little on nights that drop near freezing.

For mixes with a water-cementitious ratio below 0.40, ACI says water is needed during curing. Above that, holding in the water already in the mix may be enough, which is why plastic and curing compound work.

How to cure concrete

ACI lists the standard curing methods. They fall into two groups: ones that add water, and ones that seal water in.

Method	How it works	Where it fits
Wet burlap or cotton mats	Laid on and kept soaked	Slabs, steps, small pads
Continuous sprinkling or soaker hose	Keeps the surface wet	Flatwork when someone can tend it
Ponding	Water held on the slab by a small dike	Level slabs
Plastic sheeting	Traps the mix water; lap seams and weigh the edges	Slabs and walks
Liquid curing compound	Sprayed film that seals water in	Large or broom-finished slabs
Leaving forms in place	Protects edges and sides from drying	Footings, steps, slab edges

Wet methods only work if they stay wet. Burlap that dries out in the afternoon sun stops doing its job, so check it morning and evening.

Using a curing compound

Curing compound is the easiest method to keep up, because once it’s on, there’s little to tend. Ohio DOT’s membrane-curing method shows how it’s done right:

• Apply it immediately after the free water on the surface disappears.
• Put it on at no less than 1 gallon per 200 square feet, as a continuous film.
• Reapply anywhere the film gets damaged.

Ohio DOT also requires the membrane to be removed where waterproofing goes on later. If you plan to seal, stain or coat the slab, check that the compound you use won’t get in the way.

Watering new concrete

Watering is a curing method, not a finishing aid. Ohio DOT’s spec bars adding water to concrete between the truck and the curing step, so don’t sprinkle the surface to make it easier to trowel.

Once the slab is set and curing starts, the job is to keep it continuously wet or sealed. ACI’s guidance is simple: curing water replaces water the concrete loses. If plastic or compound keeps it from losing any, you don’t need to add more, unless the mix has a water-cementitious ratio below 0.40.

Curing in hot, cold and windy weather

Heat and wind. Hot, dry or windy days dry the surface quickly, so start curing right after finishing. ACI notes that higher temperatures give higher early strength but lower later strength.

Cool weather. Below 50°F, strength gain slows; below 40°F, hydration is greatly retarded. Extend the moist cure and keep the slab covered.

Freezing. ACI says fresh concrete must be protected from even one freeze until it reaches 500 psi, and until 3,500 psi if it will see freeze-thaw cycles while saturated. If you heat an enclosure around the pour, keep the concrete moist, because heated winter air dries it fast. Ohio DOT, for example, keeps the concrete above 32°F for 7 days in cool weather, or until a strength test passes, but never for less than 5 days.

When to strip forms and seal

Taking the forms off

Side forms on a slab can come off once the edges are hard enough not to chip or slump. If they come off early in the curing period, cure the exposed sides too: Ohio DOT requires faces stripped before 7 days to be drenched and covered with wet burlap, or coated with curing compound, depending on the curing method.

Forms that carry weight, like shoring under a landing or a suspended slab, are a different matter. Leave them until the person who designed the pour says it’s ready.

Sealing new concrete

Seal only after curing is complete and the surface has dried out. Ohio DOT applies its sealer after curing and once the deck is thoroughly dry. For a patio or driveway, follow the sealer’s label for how long to wait.

DIY or hire it out

Curing is the most forgiving part of a concrete job to do yourself: a roll of plastic, a sprayer of compound and a week of attention. The pour and finish are what decide whether a slab comes out right, and a missed curing week can undo good finishing.

Hire it out when the slab carries vehicles, the pour runs into cold weather, or you can’t place and finish it in one go. Our guide to how thick a concrete patio should be covers the slab itself, and our free patio planning kit helps you lay out size and materials before you call anyone.

Related: All our concrete guides in one place

Frequently Asked Questions

How long does concrete take to cure?

It sets within hours, should be kept moist for at least 7 days, and reaches the strength it was ordered for at 28 days. Cool weather slows all of it.

How long should I keep concrete wet?

At least 7 days, which is what Ohio DOT’s spec requires for wet burlap. Extend it when temperatures run between 40 and 60°F.

Does concrete keep getting stronger after 28 days?

It can, as long as it stays moist and above 50°F, the conditions ACI says continued strength gain needs. 28 days is the age strength is specified at, not when the reaction stops.

Should I use plastic or curing compound?

Either works. Plastic needs to stay lapped and weighed down for the full period; compound is one spray if it’s applied right after the surface water disappears at the labeled rate.

Can concrete cure in cold weather?

Yes, but slowly. Below 40°F hydration is greatly retarded, and fresh concrete has to be protected from freezing until it reaches at least 500 psi.

Sources: ACI Frequently Asked Questions: What is curing? (FAQ 789), American Concrete Institute; ACI FAQ 791: How do I know if curing is adequate?; ACI FAQ 793: Curing methods; ACI FAQ 794: Curing and temperature; ACI FAQ 795: Protecting fresh concrete from freezing; Ohio DOT 2013 Construction and Material Specifications, Item 511 Concrete for Structures (511.08, 511.12, 511.14, 511.19); 2021 International Residential Code, Chapter 4, Table R402.2, ICC

Written and reviewed by Thayne Muthler, owner of Muthler Landscaping & Construction. How we check facts: editorial policy.