Concrete Curing Blankets: Cold Weather and Moisture
Concrete curing blankets come in two main types: insulated blankets that trap the heat concrete produces so it can cure in cold weather, and absorbent wet curing blankets that hold water against the surface in warm weather. Insulated blankets are standard for winter pours, often left in place for several days until the concrete reaches enough strength to resist freezing. Contractors rent or own them; homeowners can rent them from equipment yards for small jobs.
Concrete calculator →Two kinds of blankets
| Type | Construction | Use |
|---|---|---|
| Insulated | Closed-cell foam or batting in a vinyl or poly shell | Cold weather heat retention |
| Wet curing | Absorbent fabric, often with a plastic backing | Moisture retention in mild or hot weather |
| Heated | Electric heating elements | Extreme cold, frozen ground thawing |
Why concrete needs protection in cold
Concrete gains strength slowly below about 50°F and can be damaged if it freezes before reaching roughly 500 psi. Hydration produces heat, and insulated blankets keep that heat in. See pouring concrete in cold weather.
How to use insulated blankets
- Have blankets on site before the pour.
- Thaw the ground first if frozen; never pour on frozen subgrade. Blankets or heaters can thaw it ahead of time.
- Place blankets after finishing as soon as the surface can be covered without marking.
- Overlap seams and weight the edges so wind cannot lift them.
- Extend past edges of the slab, where heat loss is highest.
- Leave in place typically 3 to 7 days, depending on temperatures and mix.
How long to leave them on
Depends on air temperature, slab thickness, and mix. Thin slabs lose heat faster. High early mixes gain strength faster. A common practice is to keep blankets on until the concrete has had several days above freezing internally. Remove them gradually to avoid thermal shock from a sudden temperature drop.
Combining with other cold weather steps
- Hot water and heated aggregates at the plant.
- Accelerators. See calcium chloride in concrete and non-chloride options.
- High early strength mixes. See high early strength concrete.
- Windbreaks and enclosures for vertical work.
Wet curing blankets
In warm weather, absorbent blankets keep water against the surface with less frequent rewetting than burlap. See wet curing concrete.
Buying or renting
Rental yards often stock insulated blankets in sizes like 6 x 25 feet. For a single small slab, renting is usually cheaper. Straw and plastic are an old-school alternative but are less consistent.
Bottom line
Insulated curing blankets keep concrete warm enough to gain strength in cold weather; wet curing blankets keep it moist in heat. For winter pours, cover promptly after finishing, overlap edges, leave blankets on several days, and remove them gradually.
Questions people ask
How long do you leave curing blankets on concrete?
Often 3 to 7 days in cold weather, depending on temperature and mix.
Can I pour concrete in freezing weather with blankets?
With proper planning, yes, but never on frozen ground. Thaw the subgrade first.
Do curing blankets keep concrete from freezing?
Insulated blankets retain the heat concrete generates, helping prevent early freezing.
Can I use straw instead of curing blankets?
Straw covered with plastic is an old method, but insulated blankets are more reliable.
Where can I rent concrete curing blankets?
Equipment rental yards and some concrete supply houses rent them.
Related guides
- Pouring Concrete in Cold Weather: Rules and Tips
- Wet Curing Concrete: Methods, Timing, and How Long
- High Early Strength Concrete: When Speed Matters
- Calcium Chloride in Concrete: Accelerator Pros and Cons
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