Oct 14, 2019 | Concrete Tips

How to Protect Late Season Concrete Pours

Arnold Ready Mix worker smoothing out concrete

Concrete can be poured even in cold Missouri weather, but the process for late season concrete pours differs from concrete 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 it is a late season concrete pour in cold weather, it needs to be protected from freezing right after being poured. The concrete also needs to be strong enough to remove the forms at the right time without using excessive heat to help it develop the needed strength. So, proper curing conditions must be used to prevent cracking and maintain the serviceability of the needed structure for late season concrete pours across Missouri.

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 set. 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, 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 the concrete’s cold weather protection measurement and design are.
  3. Temperature chart: A temperature chart of the concrete and exterior temperatures should also 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 of cold weather concrete.
  • Cold-weather concrete needs to have a low slump with a minimum water-to-cement ratio to reduce the setting time and decrease water bleeding.
  • Heated enclosures or blankets should be used to maintain the concrete temperature above 50 degrees for three to seven days. Concrete curing blankets can also be used to maintain 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 a heated mix of concrete. Having the extra cement if the mix isn’t heated will help 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 using insulated blankets or enclosures that are heated, maintain the concrete at a temperature above 40 degrees Fahrenheit for at least four 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 is possible if the procedures are followed properly.

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