Concrete Curing Time Chart

These charts give the numbers in one place: how many days concrete takes to gain strength at two temperatures, how long each cement type should be cured, and when you can walk, drive and seal. For the plain-language timeline and what to do day by day, see how long concrete takes to cure.

How many days does concrete take to reach strength at each temperature?

At 70°F (21°C), Type I concrete reaches 85% of its standard 28-day strength in about 16 days. At 50°F (10°C) it takes about 21. The chart below is ACI 306R’s table of how long to protect concrete to reach each strength level, as reproduced by the Federal Highway Administration.

The percentages compare against “standard-cured” 28-day strength, meaning cylinders kept moist at lab temperature. The Type III cell at 70°F and 65% is left blank because FHWA flags the printed value as an error. Type III is the high early strength cement; Type II is the moderate heat cement that gains strength more slowly.

How long should each cement type be cured?

High early strength (Type III) concrete needs about 3 days of curing, ordinary Type I needs 7, and Type II needs 14. The older ACI 308 guide (1992), as summarized by FHWA, gives those three and skips Types IV and V, pozzolans and slag. The Army Corps guide spec in the same FHWA appendix covers blended mixes.

Current spec work follows ACI 308.1: 7 days with the concrete above 50°F (10°C), or until tests show 70% of specified strength. For pavements, the FHWA appendix lists ACI’s version at 7 days above 41°F (5°C) or 70% strength.

When can you walk, drive and seal new concrete?

Walk on it at 24 to 48 hours, drive a car on it at 7 days, and seal it at about 30 days. Those are general guidance from state concrete associations for normal conditions, around 70°F, so add time in cold weather.

The heavy truck figure varies most between sources. Virginia’s association says at least 6 months for a residential driveway, while some contractor guides say 28 days. If a loaded truck has to cross a new slab sooner, ask your ready mix supplier what strength the mix will have by then.

How does temperature change concrete curing time?

Colder concrete gains strength more slowly, and the effect is large. NRMCA’s cold weather guide says “a drop of 20°F [10°C] in concrete temperature will approximately double the setting time.” The Michigan association adds that hydration slows sharply below 50°F (10°C) and “below 40 degrees, it can stop almost entirely.”

Hot is not better. NRMCA’s hot weather guide says concrete cured at high temperatures early “will not be as strong at later ages” as the same mix cured around 70°F (20°C). In summer, cure it wet or sealed for at least 3 days and follow the hot weather curing steps.

Does a frozen or cold slab ever catch up?

A slab that stayed cold but never froze keeps gaining strength once it warms, just later. A slab that froze while fresh is different: NRMCA says “the potential strength of frozen concrete can be reduced by more than 50%.” It also says to protect concrete from freeze and thaw cycles until it reaches 3,500 psi (24 MPa).

The NRMCA curing guide asks for placed concrete to be kept above 50°F (10°C) during curing. For blankets, heaters and the rest, see cold weather concrete curing.

If you need the slab sooner than the chart allows

If the schedule is tight, change the mix before the pour, not the curing after it. NRMCA’s cold weather guide lists high early strength Type III cement, extra cement and accelerating admixtures as ways to speed strength gain, plus keeping the concrete warm with insulating blankets or heated enclosures.

Two limits apply. Accelerators do not stop concrete from freezing. Calcium chloride, the common accelerator, is capped at 2% by weight of cement. And no shortcut replaces the curing itself: keep the slab wet or sealed through the days in the cement type table above.

For a one page printout of these numbers, use the concrete curing cheat sheet.