Curing concrete
How Long Does Concrete Take to Cure?
You can walk on new concrete after about 24 hours and park a car on it after about 7 days, when it has roughly 70% of its strength. It reaches design strength at 28 days. Keep it wet or sealed for the first 7 days, and expect every step to take longer below 50°F (10°C).
New concrete gets hard in a day, carries a car in a week and hits the strength it was designed for at 28 days. Those three numbers hold for a normal mix in mild weather. Cold, heat, wind and skipped curing all move them, so the timeline below comes with the conditions that change it.
How long does concrete take to cure, day by day?
Plan on 24 hours before you walk on it, 7 days before a car, and 28 days before heavy trucks. Every number in this table links to the source that gives it. They assume a normal residential mix placed at 50°F (10°C) or warmer and kept moist.
| When | What you can do | Source |
|---|---|---|
| First minutes | Start curing right after placement and finishing | IRMCA homeowner guide |
| 24 hours | Light foot traffic | ConcreteNetwork walk-on guide |
| 48 hours | Heavier foot traffic | ConcreteNetwork walk-on guide |
| 3 days | Bikes, scooters, skateboards | ConcreteNetwork driveway guide |
| 7 days | End of the minimum curing period; passenger cars, at about 70% strength | IRMCA, ConcreteNetwork driveway guide |
| 28 days | Design strength test age; RVs and large trucks | NPCA on the 28-day test, ConcreteNetwork driveway guide |
| About 1 month | Air dried enough to seal | IRMCA |
| First winter | No deicing chemicals; use sand for traction | IRMCA |
| Years | Strength keeps creeping up while moisture remains | American Cement Association |
For the same milestones broken out by air temperature, see the concrete curing time chart.
What is the difference between curing, drying and setting?
Setting is the concrete going from plastic to hard, which happens in hours. Curing is keeping water and warmth in the slab so the cement keeps reacting and gaining strength. Drying is water leaving the slab, and it works against curing in the first week.
The American Concrete Institute puts it plainly in ACI 308R-16: the curing period “begins at placing and continues until the desired concrete properties have developed.” A slab that looks dry and feels hard on day two is set, not cured.
Drying out early costs real strength. The National Ready Mixed Concrete Association says concrete in a dry environment can lose as much as 50 percent of its potential strength compared with moist-cured concrete. The surface suffers most: more dusting, crazing and wear.
How long do you keep concrete wet?
Keep new concrete wet or sealed for at least 7 days. The Indiana Ready Mixed Concrete Association says curing “should commence within minutes after placement and extend a minimum of 7 days.” NRMCA gives 3 to 7 days as typical, so 7 is the safe homeowner number.
It has to stay wet the whole time. NRMCA says alternate wetting and drying is not an acceptable curing practice. The ACI 308R guide notes that early hydration can stall once the air around the paste drops to 90 percent relative humidity or less, so a slab that dries between hosings stops gaining strength each time.
What counts as curing?
Any method that holds the water in or keeps adding it for the full period. The IRMCA homeowner guide lists four:
- Spray-on curing compound, applied once the water sheen is gone
- Polyethylene sheeting laid flat on the slab
- A 7-day continuous water cure (sprinkler or soaker hose)
- Wet burlap covered with polyethylene
Curing compound is the easiest for a homeowner because it works once and needs no babysitting. Timing matters: spray too soon and you trap bleed water, too late and the surface has already dried. See when to apply curing compound for the cue to watch for, and the concrete curing methods compared for pros and cons of each.
When can I drive on new concrete?
Park a passenger car on a new driveway after about 7 days. By then a normal mix has about 70% of its potential strength. Keep RVs, large pickups with trailers, moving vans and garbage trucks off for at least 28 days.
The Virginia Ready Mixed Concrete Association is more cautious and says heavy trucks should stay off a new driveway for at least 6 months.
The National Precast Concrete Association puts the 7-day figure a bit higher, at about 75% of 28-day strength, and notes a typical spec calls for 4,000 to 5,000 psi (28 to 34 MPa) at 28 days. Either way, the edges are the weak point in week one. ConcreteNetwork advises staying off the edges when you first drive on it.
Those numbers assume the slab stayed above 50°F (10°C). A driveway poured in cold weather gains strength slower and needs a longer wait. Ask your contractor, who knows the mix and the overnight lows.
What does ACI 308 require for curing time?
For contractors, the spec answer is 7 days or 70%. The FHWA summary of ACI 308.1 says “the default curing time is 7 days if the temperature is greater 10 °C,” and curing “may be terminated early if strength is at least 70 percent of f’c.”
That 70% has to be shown by strength testing, not assumed.
The same FHWA appendix notes the older ACI 308 guide split curing length by cement: 3 days for Type III, 7 days for Type I and 14 days for Type II. That guide gave no number for mixes with fly ash or slag, so get the curing period for those from the spec or the supplier.
Project specs override all of this. If the spec says 10 days wet cure, it is 10 days.
How does temperature change concrete curing time?
Warm concrete gains strength faster, cold concrete slower, and below freezing it can be ruined. NRMCA says placed concrete should be kept above 50°F (10°C). Below that, every milestone in the table moves later.
Cold weather
Protect the slab from freezing until it reaches at least 500 psi (3.5 MPa), using insulated blankets. NRMCA also says not to let it cool faster than 5°F (3°C) per hour for the first 24 hours. In freezing weather, use curing methods that hold moisture in rather than wet curing. More detail is in cold weather concrete curing.
Hot weather
Heat speeds early strength gain, but NRMCA warns that higher early curing temperatures lead to lower ultimate strength. Hot, dry and windy conditions also pull water out of the surface fast, which is when plastic shrinkage cracks show up. Cure early and keep it wet.
Rain
Rain on concrete that has not set can wash out the cement paste and pit the surface. Have plastic sheeting on site before the truck shows up. Once the surface is hard and the curing method is in place, light rain does no harm and actually helps a water cure.
Does concrete ever stop curing?
Not entirely. The American Cement Association says most of the hydration and strength gain take place within the first month, “but hydration continues at a slower rate for many years.” It slows to almost nothing once the slab dries out.
That is why 28 days is a test age, not a finish line. Engineers design and test to 28-day strength because it is a fair point to compare mixes. NPCA notes that after 28 days, strength will remain stable or even increase over time.
If you drove on it early or it froze
Most early traffic does no harm you can see. Check the edges and corners for cracks or crumbling where tires ran, and stay off it until day 7. A hairline crack is cosmetic in most cases. A broken corner or a sunken edge needs your contractor back out.
If the slab froze in the first day or two, look for a soft, flaking or scaling surface in the next few weeks. Freezing in that window can leave a weak, scaling surface, because the slab had not yet reached the 500 psi NRMCA uses as the protection threshold. Get the contractor to look before you seal it.
What should you ask your concrete contractor?
Ask before the pour, while you can still change the plan. These five questions cover the timeline:
- What curing method will you use, and who keeps it in place for 7 days?
- Does the mix have fly ash, slag or accelerators that change the timeline?
- What are the overnight lows for the next week, and do you have blankets?
- When can I park a car on it, and when can a delivery truck pull in?
- When can I seal it, and what sealer works over your curing compound?
Frequently asked questions
How long should concrete cure before putting weight on it?
Light foot traffic after about 24 hours, heavier foot traffic after 48 hours, bikes and skateboards after 3 days, cars after about 7 days, and RVs or large trucks after at least 28 days. Cold weather stretches every one of those.
When can I drive on new concrete?
A passenger car can usually go on a new driveway about 7 days after the pour, when the slab has about 70% of its strength. Stay off the edges at first, and keep RVs, moving vans and other heavy vehicles off for at least 28 days. One state ready mix association says 6 months for heavy trucks.
How long do you keep concrete wet?
At least 7 days. Start within minutes after placement and keep the surface continuously wet, or seal the water in with plastic sheeting or a curing compound. Letting it dry out between waterings does not count as curing.
Does concrete ever stop curing?
Not completely. Most of the strength gain happens in the first month, but cement keeps hydrating at a slower rate for years as long as there is moisture in the concrete. The 28-day number is a test age, not an end point.
Does concrete cure faster in hot weather?
It gains early strength faster, but hot curing can lower its later strength, and hot, dry, windy days pull water out of the surface. In summer, keep it wet or covered and do not cut the curing period short.