The Constructor

Cold Weather Concreting: Guidance, and Strategies

Cold Weather Concreting

Reading time: 1 minute

Cold weather concreting is the process of placement, finishing, curing, and protection of concrete during cold weather, as per ACI 306.1. The cold weather occurs when the average outdoor temperature is below 4.4C (40F) for more than three successive days. If the temperature of fresh concrete is 12.7C (55F) or greater, and if the concrete is maintained at this temperature, then winter concreting should be free from problems.

Approximate set time for concrete at 21C (70F) is six hours. Set time jumps to just over 14 hours if the concrete temperature drops to 4.4C (40F). If it drops below this point and the concrete freezes early in the process, loss of strength, up to 50 percent, increased permeability and a lower resistance to weather may result.

The key is to start with warm concrete and keep it warm. The internal heat of the concrete mix may be raised by heating the materials, using extra or special cements, or by the addition of accelerators. The environment may be also altered by using enclosures and moist heat, applying insulating blankets, polystyrene sheets, or hay, and leaving the forms in place.

Guidance and Strategies for Cold Concreting

1. Preparations

2. Concrete Pouring

Table 1 Minimum Concrete Temperature Immediately After Pouring and during the protection period

Least dimension of section, cm (in) Minimum temperature of concrete as placed and maintained during the protection period, C (F)
Less than 30.5 (12) 12.7 (55)
30.5 (12) to less than 91 (36) 10 (50)
91 (36) to less than 193 (76) 7.2 (45)
Greater than 193 (76) 4.4 (40)
Fig. 1: Concrete Pouring in Cold Weather

3. Concrete Protection

Fig. 2: Concrete Protection in Cold Weather

4. Concrete Curing

  1. Cure concrete to prevent the loss of moisture.
  2. When heated enclosures are used, provide extra moisture by sprinkling or use steam for heating. Vent salamanders and other fuel-burning heaters. Concrete should be allowed to cool slowly to prevent thermal cracking.
  3. Leave the forms in place if the job schedules permit.
  4. Reshoring is necessary until concrete reaches required design strength.
  5. If the concrete is to cure below 15.5 (60F), water reducers or retarders may prolong the set. Concrete placed in late fall or winter should not be exposed to salts applied as deicers or salts which drip from parked vehicles.
Fig. 3: Concrete Curing in Cold Weather
Exit mobile version