How to Protect Late Season Concrete Pours

Concrete can be poured even in cold Missouri weather, but the process is different than concrete being poured in warm weather. Now the American Concre...
Tuesday, 13 December 2016 00:17

Concrete can be poured even in cold Missouri weather, but the process is different than concrete being poured in warm weather. Now the American Concrete Institute under ACI 306 defines that concrete is exposed to cold weather under certain conditions. These conditions are when the daily average air temperature is less than 40 degrees Fahrenheit and within a 24-hour period the air temperature isn’t greater than 50 degrees Fahrenheit for more than one half of the time.

In addition, if concrete is being poured in cold weather, it needs to be protected from being frozen right after being poured. Too, the concrete needs to be strong enough to remove the forms at the right time without having to use excessive heat to help the concrete develop the strength that’s needed. So, proper curing conditions need to be used to prevent cracking and still have the serviceability of the needed structure.

Steps for pouring concrete in cold weather

There are certain steps that need to be followed so that concrete has the designed strength that’s required as well as avoiding other problems that can occur when concrete is setting. Below are these steps:

  1. Before pouring: Before the concrete is poured, the concrete purchaser should discuss with the concrete company what strategies will be used with the materials, the forms and how the concrete will be tested and any other requirements that are of concern.
  2. Ordering the concrete: When scheduling the concrete delivery, it should be determined what is the cold weather protection measurement and design of the concrete.
  3. Temperature chart: A temperature chart of the concrete temperature and the exterior temperature as well should be kept. An infrared thermometer can be used to check the concrete temperature.
  4. When not to pour: Concrete should never be poured over ground that’s frozen, has snow on it or is ice covered. If the ground is frozen, thaw it out with heaters.
  5. Determination: It should be determined whether the strength requirements and special considerations are being met by the contractor in a reasonable way all through the job. If needed, the concrete should be protected at the specific temperatures that are required.
  6. Heated enclosures: Windproof and weatherproof heated enclosures are the only type of enclosures that should be used when placing concrete in cold weather.

Other tips

Here are some other facts for concrete purchasers listed below for pouring concrete in cold weather:

  • If you’re using combustion heaters, be sure the heaters are vented to the outside to prevent carbon-monoxide poisoning,
  • The correct amount of air entrained voids should be used for the concrete to resist the thawing and freezing effects on cold weather concrete.
  • To reduce the setting time and decrease water bleeding, cold weather concrete needs to have a low slump with a minimum water to cement ratio.
  • To maintain concrete temperature at above 50 degrees for three to seven days, heated enclosures or heated blankets should be used. Also, concrete curing blankets can be used to keep an optimal curing temperature.
  • Finishing operations should not be started while there is bleed water present.
  • For each cubic yard of concrete, order an extra 100 pounds of cement; or order a heated mix of concrete. By having the extra cement if the mix isn’t heated, this will help to develop concrete strength early.
  • If your concrete becomes frozen within the first 24 hours, it can lose up to 50% of a 28-day strength potential.

After the use of insulated blankets or enclosures which are heated, maintain the concrete at a temperature of above 40 degrees Fahrenheit for at least 4 more days. How to do this can be found under ACI 306 guidelines.

  • The temperature of concrete, within 24 hours, can’t drop to lower than 40 degrees Fahrenheit. If it’s dropping lower and you have no other option, add a bag of cement mix.
  • Until the concrete has bled and the setting process has begun, don’t seal it.
  • Wind, rain and snow affect the temperature of poured concrete negatively.

Pouring concrete in Jefferson County Missouri during cold winters can be done if the procedures are followed properly.

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