Cold weather concreting presents some special problems, especially if temperatures are below freezing. Cold weather concreting practices should: prevent damage caused by freezing at early ages; protect concrete until it reaches necessary strength levels; allow concrete to cool gradually when protection is removed so that a rapid temperature drop doesn't cause it to crack. To prevent damage caused by early freezing, the amount of water in the concrete must be reduced before the concrete is exposed to cold weather. When structures will be fully loaded soon after placing in cold weather, the concrete should be protected until the required strength is achieved.
When cold weather is expected, thorough and careful planning is needed to avoid problems: 1) select a concrete mix suitable for cold weather; 2) specify the minimum allowable concrete temperature as mixed, based upon air temperature and thickness of sections to be placed; 3) determine the types of protection that are likely to be required: insulating blankets, insulated wall forms, enclosures and/or heaters.
DELIVERY, PLACING AND FINISHING
Delays in delivery or delays at the jobsite can cause concrete temperatures to drop below the specified minimum temperatures. The producer and contractor should coordinate operations to minimize waiting time.
CURING AND PROTECTION
Avoid water curing. It produces icing problems and increases the likelihood of concrete freezing in a saturated condition when the protection is removed.