Concrete Curing Blankets: When to Use Them

Concrete Curing Blankets: When and How to Use Them

Curing blankets are mandatory when temperatures drop below 40°F at night. They trap heat from the concrete's hydration reaction, keeping it warm enough to cure properly. Without them, concrete freezes and is permanently damaged. This guide covers exactly when and how to use curing blankets.

When Curing Blankets Are Mandatory

Curing blankets are required when:

Temperature Drops Below 40°F at Night

This is the critical threshold. Below 40°F, concrete loses heat faster than the hydration reaction generates it, causing the temperature to drop toward freezing.

Concrete Temperature Would Drop Below Freezing

Even if air temperature is above freezing, concrete can still freeze if it's losing heat faster than it's generating it.

Any Time Freezing is Possible

If there's any chance concrete could freeze, use blankets. Freezing during curing is permanent damage—prevention is the only solution.

How Curing Blankets Work

Understanding the mechanism helps you use them correctly.

The Heat Source: Hydration Reaction

Concrete generates heat as it cures. The chemical reaction between cement and water (hydration) is exothermic—it produces heat. This heat helps keep concrete warm during curing.

How Blankets Help

Curing blankets:

Trap heat: Insulation prevents heat from escaping
Maintain temperature: Keep concrete warm enough to continue curing
Prevent freezing: Ensure temperature stays above 32°F

The Science

Without blankets, heat escapes to the cold air. Concrete temperature drops. If it drops below freezing, hydration stops and concrete is damaged. Blankets create an insulating barrier that traps heat, keeping concrete warm enough to cure.

How to Use Curing Blankets

Proper application ensures effective protection.

Step 1: Choose the Right Blanket

Insulated curing blankets: Specifically designed for concrete (best option)
Thickness: Typically 1-2 inches of insulation
Coverage: Large enough to cover entire concrete plus edges

Step 2: Apply Immediately After Finishing

Timing: Cover as soon as finishing is complete
Don't wait: Heat starts escaping immediately
Before temperature drops: Get blankets on before nightfall

Step 3: Cover Completely

Full coverage: Cover entire concrete surface
Overlap edges: Extend 6-12 inches beyond concrete edges
Multiple layers: In extreme cold, use multiple layers

Step 4: Secure Blankets

Weight edges: Use sandbags, bricks, or stakes
Prevent gaps: Ensure blankets stay in contact with concrete
Check regularly: Ensure blankets stay in place

Step 5: Monitor Temperature

Check concrete temperature: Use temperature probe if possible
Ensure above 50°F: Concrete needs to stay warm for proper curing
Never below 32°F: Freezing must be prevented

Step 6: Keep Covered Duration

Minimum: 3-7 days
Longer in extreme cold: May need 7-14 days
Until concrete gains strength: Don't remove too early

Temperature Requirements

Concrete must maintain:

Minimum: 50°F for proper hydration
Never below: 32°F (freezing point)
Ideal: 70-80°F for fastest, best curing

When to Use Multiple Layers

In very cold conditions, use multiple layers:

Extreme cold: Below 20°F air temperature
High wind: Increases heat loss
Large surface area: More surface area = more heat loss

Warning Signs

Signs that blankets aren't working:

Frost on blanket or concrete: Immediate action needed
Cold concrete: Temperature dropping
Concrete not setting: May indicate freezing

What Happens Without Blankets

If concrete freezes during curing:

Hydration stops: Chemical reaction cannot occur in frozen concrete
Permanent damage: Concrete will never reach full strength
Surface scaling: Top layer can pop off
Internal damage: Expansion from freezing creates cracks

There's no fixing frozen concrete. Prevention is the only solution.

The Bottom Line

Curing blankets are mandatory when temperatures drop below 40°F at night. They trap heat from the concrete's hydration reaction, keeping it warm enough to cure. Apply immediately after finishing, cover completely, secure edges, and keep covered 3-7 days minimum. Monitor temperature to ensure it stays above 50°F (never below 32°F). Without blankets in cold weather, concrete freezes and is permanently damaged.

Don't skip blankets in cold weather—the cost of replacement is far greater than the cost of proper protection.

Need to pour in cold weather? Contact Local Concrete Contractor. We have the experience and equipment to ensure proper protection and successful cold-weather concrete placement.