Below about 40 F (4 C) hydration slows sharply, and concrete that freezes before reaching roughly 500 psi can lose much of its eventual strength. Cold weather plans call for heated water and aggregate, accelerators, insulated blankets, heated enclosures and temperature monitoring, and they forbid placing on frozen subgrade. Unvented heaters inside enclosures can carbonate the fresh surface and cause dusting.
Cold weather concreting rules from tonight, so blankets on the footings and every heater in the tent vented outside.
Fresh concrete needs to stay above freezing until it reaches about 500 psi, which usually takes one to two days under blankets.
Also heard as
- winter concreting
- cold weather protection
- winter protection
Related terms
Accelerator
An admixture that speeds up setting and early strength gain, mostly used in cold weather.
Curing
Keeping fresh concrete moist and warm enough, for long enough, that the cement keeps hydrating.
Dusting
A soft, powdery concrete surface that rubs off under traffic or a scraped fingernail.
Maturity method
Estimating in-place concrete strength from its temperature history, recorded by sensors cast into the pour.
Type III cement
High-early-strength portland cement, ground finer so concrete gains strength in days instead of weeks.