Cold Weather Concreting: Tips for Achieving a Successful, High-Quality Placement
While most of society “hunkers down” when winter weather begins, for players in the construction industry, the project must go on. There are no snow days or slowing down of schedules when the days get shorter and colder—which creates challenges for even the most experienced of contractors.
Placing and curing concrete during the winter months—even those considered relatively “mild” for winter—presents obstacles that need to be overcome at the jobsite. As ambient temperatures plummet, concrete temperatures fall as well, resulting in a slower rate of cement hydration, set times, and strength development. Dealing with frozen subgrades, preventing early-age freezing, ensuring concrete develops the desired strength, and avoiding cracks or other surface defects are just some of the potential problems that need to be considered in upfront planning.
According to the American Concrete Institute (ACI 306), cold weather exists when the air temperature has fallen to or is expected to fall below 40 °F during the protection period. Effective protection allows the concrete to gain strength at a normal rate and prevents the concrete from early-age damage by freezing. For most concrete maintained at 50 °F, the protection period lasts until the concrete reaches a saturation level below 92% and attains a minimum strength of 500 psi, which is about 48 hours after placement.
When working in severe cold temperatures during winter season, producers and contractors can mitigate risks and obtain a high-quality finished product by making modifications to their concrete mix designs and implementing a variety of preventive measures and best practices.