Concrete · Emergency

Concrete emergencies

Genuine concrete emergencies are few: a trip hazard or displaced slab on a walkway, a slab settling near a foundation or over a suspected washout, and a fresh pour facing freezing temperatures before it has gained strength. Cracks, scaling and discoloration are not emergencies — document them and address them on a normal timeline.

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During a pour, the time-critical failures are weather and timing. NRMCA says fresh concrete must be protected from freezing until it reaches at least 500 psi, using insulating materials, and must not cool faster than 5°F per hour for the first 24 hours. If a hard freeze is coming and nobody has blankets on your slab, that is a same-night phone call.

The other clock is jointing. Conventional sawcuts should be run within 4 to 12 hours of finishing; if the crew has gone home and 24 hours have passed with no cuts on a large slab, the slab may crack where it chooses. Call, in writing, and note the time.

Rain on a fresh, unfinished surface is a real problem — it adds water to the top layer and weakens it. Rain on a slab that is already finished and covered is usually survivable. NRMCA's related point: alternate wetting and drying is not an acceptable curing practice.

After the fact, the safety emergencies are displacement — a slab section sitting higher than its neighbor on a path people use — and settlement near a foundation, which may indicate soil loss from a leak or drainage failure. Both mean stop using the area and get eyes on the cause, not the surface.

How to choose

Freeze warning on a fresh pour: act tonight: Ask specifically about insulating blankets and protection until the slab reaches 500 psi. This cannot be fixed the next morning.
No joints cut after 12+ hours: call and document: NRMCA's window for conventional saw cutting is 4 to 12 hours after finishing. Missing it invites random cracking.
Barricade any trip hazard immediately: A displaced walkway slab is a liability issue before it's a repair issue. Cone it or tape it the same day.
Settlement near the house means look for water: Soil doesn't vanish on its own. Check downspouts, grading, and irrigation lines before paying for slab lifting.
Rain during finishing: get photos: Whether water was worked into the surface determines who owns a scaled slab in two years.
Cracks are not emergencies: Most early random cracks don't affect structural integrity per NRMCA. Photograph, date, and address them calmly.

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FAQ

Concrete emergency — common questions

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It's going to freeze tonight and the concrete was poured today. What now?

Contact the contractor immediately. NRMCA requires protecting concrete from freezing until it reaches at least 500 psi using insulating materials, and not allowing it to cool faster than 5°F per hour during the first 24 hours. Curing methods that retain moisture rather than add water should be used when freezing is expected.

It rained on my new concrete. Is it ruined?

Not necessarily. The damaging case is rain landing on an unfinished surface, adding water to the top layer. If it was already finished and covered, it is often fine. Photograph the state of the slab and the time, and ask what protection was in place.

A section of my walkway has lifted. Do I have to fix it now?

Treat it as a safety issue first — mark or barricade it. Displacement means movement under the slab, so the fix should start with finding out why, not just grinding the lip.

The crew left without cutting joints. Does that matter?

Yes. NRMCA specifies conventional saw-cut joints within 4 to 12 hours after finishing, or early-entry cuts 1 to 4 hours out, and notes that if delayed too long, uncontrolled cracking may occur. Raise it immediately and in writing.

Sources

Where these figures come from

NRMCA CIP 11 — Curing In-Place Concrete · retrieved 2026-07-25
NRMCA CIP 6 — Joints in Concrete Slabs on Grade · retrieved 2026-07-25
NRMCA CIP 4 — Cracking Concrete Surfaces · retrieved 2026-07-25