COLD WEATHER CONCRETE POURS

When one of the following conditions exists for more than three consecutive days: the average daily temperature is less than 40¾F from midnight to midnight, or the average temperature is less than 50¾F for more than half of any 24 hour period

Notes:

  • Low temperatures slow down curing time which results in lower compressive strength early in the curing process.
  • The colder it gets the longer it takes to cure.
  • The CRCA staff has observed contractors over the last several years continuing to do site preparations and concrete pours in considerably less than ideal weather conditions, such as freezing temperatures and snow. The CRCA staff realizes in today’s economy this is a necessity. It is not our intention to prohibit work in these unfavorable conditions, however many contractors are not taking some basic precautions to protect the concrete from freezing.
  • Resources for these guidelines have been taken from The American Concrete Institute, Concrete Foundation Association, local concrete suppliers and Accu-Weather.

Good Practices:

  • Avoid adding water to concrete on the job to make it “flow better”. The more water you add to concrete the more likely it is to freeze. Generally speaking, for every gallon of water per yard added to concrete at the site, you lose at least 200psi of strength.
  • When ordering concrete from your supplier, tell them to add pozzolith or pozzutec product, or a similar non-chloride additive. Chloride additives have a corrosive effect on re-bar.

Requirements:

  • Do not pour concrete on frozen ground or have ice in forms or on re-bar.
  • Poured concrete foundations have a minimum compressive strength of 3,000lbs. at 28 days and must be air entrained between 5% and 7% by volume when poured in cold weather.
  • When pouring concrete for footers and poured foundations, from November 15 to March 15, you are required to have blankets on site at the time of the inspection in order to cover the concrete.
  • The forms may be removed, but poured foundations must remain covered, and no foundation coatings may be applied, for at least one week after pouring the walls.
  • Slips from the concrete supplier must be provided at the foundation inspection in order to verify strength, if air-entrained, date poured and additives.