Cold Weather Concreting Tips and Precautions to Follow

Cold weather concreting can be a challenging task. Concrete is considered cold when it is exposed to an average daily temperature of less than 5°C or when the air temperature is not greater than 10 degrees for more than half a day, according to ACI 306. In this article, we will provide tips and precautions for pouring concrete in cold weather conditions.

Fig.1. Cold Weather Concreting; Image Courtesy: Herbert Construction

Tips for Pouring Concrete in Cold Weather

When pouring concrete in cold weather, special care must be taken to avoid freezing just after the concreting. Here are some steps to follow:

1. Plan ahead: Define the strategies required for cold weather concreting, including materials, formwork, testing, and other requirements.
2. Schedule and determine the cold weather protection measurement of the concrete mix.
3. Prepare a well-defined temperature record chart that specifies both the concrete temperature and exterior temperature.
4. Do not pour concrete on the ground that is frozen with snow or ice. Heaters can be employed to thaw the ground base before pouring the concrete.
5. Protect the concrete for specific temperatures based on the strength requirements.
6. Ensure that the heat enclosures used for placing the concrete in cold weather are windproof and weatherproof. If the concreting employs combustion heaters, prevent carbonation by venting the process.
7. Design the cold weather concrete mix with a sufficient amount of air-entrained voids to resist the freezing and thawing effects.
8. Use a lower slump value and lower water-cement ratio for the cold weather concrete mix to decrease bleeding and setting time.
9. Use curing blankets to help prevent freezing and maintain the curing temperature.
10. Use insulation blankets to maintain the concrete temperature above 5°C for three to seven days.
11. Do not finish the concrete surface when there is bleeding water above the surface.
12. Do not let the temperature of the concrete fall below 5°C within 24 hours.
13. Start sealing the fresh concrete when the setting process has started.
14. If the batching plant and the final concreting destination are far, special care must be taken to reduce setting issues.
15. Note that around 50% of the potential 28-day strength is reduced when the fresh concrete freezes.

Guidance on Cold Concreting

Aspect	Guideline
Temperature	Air and concrete temperature should be greater than or equal to 5°C at the time of placement and maintained above 0°C for 3 days after placement
Concrete mix design	Increased air content and use of set accelerators, fly ash, slag, or other cementitious materials may be required
Formwork and rebar	May need to be heated or insulated to prevent freezing and promote proper curing
Placement and finishing	Concrete should be placed and finished as quickly as possible to minimize the effects of cold weather
Curing	Proper curing is essential to ensure adequate strength gain and prevent freezing; curing blankets or other insulating materials may be required
Protection	Concrete should be protected from freezing for at least 3 days after placement

Cold Weather Concrete Checklist

1. Check the weather forecast and plan accordingly
2. Ensure that all equipment is in good working condition
3. Use of appropriate mix design with set accelerators and/or other cementitious materials
4. Heat or insulate formwork and rebar to prevent freezing
5. Ensure that the ground is not frozen before pouring concrete
6. Use heaters to thaw the ground if necessary
7. Protect freshly poured concrete from freezing with curing blankets or other insulating materials
8. Maintain proper curing temperatures for at least 3 days after placement
9. Monitor concrete temperatures and adjust protection as needed
10. Check concrete strength gain and make any necessary adjustments

Maintain Concrete Temperatures During Cold Weather

It is recommended in ACI 306 to keep the concrete warm (temperature greater than 5°C) for the first two days (strength development period). When the concrete is placed at a temperature below 5°C (a temperature not less than the freezing point), it takes longer to attain strength.

To maintain concrete temperatures during cold weather, use frost blankets and insulated blankets to protect the concrete. Beams, columns, and walls can be covered with insulated forms or temporary covers to perform curing.

Summary

Cold weather concreting requires special attention to prevent freezing and ensure the required strength is achieved. By following the tips and precautions mentioned in this article, you can successfully pour concrete in cold weather conditions. Remember to plan ahead, protect the concrete for specific temperatures, and maintain concrete temperatures during the curing process.

Also Read:

1. Top 15 Factors Affecting the Strength of Concrete
2. Stainless Steel Tying Wire In Construction