Despite below-freezing temperatures, winter construction is possible and can be high quality when the correct precautions are taken. While there are inevitable schedule delays due to high winds, snow, and extremely cold temperatures, winter construction is feasible. We’ve outlined the risks associated with this type of work, as well as the appropriate precautionary measures that must be taken to ensure a quality repair.
If there is a probability of the air temperature falling below 5°C within 24 hours of concrete placement, special precautions are required to ensure the concrete achieves the strength and durability characteristics it was designed for. Irreparable loss of up to 50% of design strength can occur if concrete freezes before sufficient strength are developed to resist the expansive force of ice formation. To protect the concrete during the crucial early stages of curing, consider the following:
1. The reinforcement, forms, and substrate should be free from dirt and ice, and above 10°C prior to placing the concrete.
2. The temperature of the concrete at the time of placement should be between 20°C and 25°C, which can be achieved by heating the aggregates, water, or both. Concrete plants should use these methods during cold weather.
3. Depending on the weather conditions, curing concrete may require protection from wind, an enclosure, or supplementary heat. Insulating blankets can be used to maintain temperature and humidity during the curing period during moderately cold weather. Supplementary heat can be applied with the use of an indirect heater to prevent carbonation (associated with steel corrosion and concrete shrinkage).
We often hear that there are two seasons in Canada: winter and construction season. We now know that the construction season can be extended year-round provided there are proper precautions taken. Proper quality control and third-party review are critical to protecting your investment on any construction project, and even more so if you are considering winter construction. By keeping a close eye on the forecast and taking proper precautions, winter construction can produce high-quality, long-lasting repairs.
Check back for Surviving the Cold – Winter Construction: EIFS!
Shawna Smigelski, B.Sc.(Eng.), P.Eng.