Cold Weather Concreting
Placing concrete for foundation walls during the winter months in Buffalo, New York is certainly challenging, however, it is not impossible. Through proper coordination and communication between Damiani Concrete Company Inc. and our redi-mix supplier, very favorable results can be obtained even during “severe” weather conditions. There are many factors to be considered when determining what mix design to use during cold weather conditions, as well as, what field practices should be followed to ensure a successful pour. Damiani Concrete Company Inc. has been pouring foundations for over forty-three years in the Buffalo, NY area in summer and winter alike and has gained a thorough understanding of the cold weather concreting practices that are required to place concrete during the winter months.
Certainly, there are weather conditions that we experience here in Buffalo that make concrete placement both risky and extremely expensive. if it is not safe to pour, don’t pour!
Here are our practices
The two biggest factors to consider in cold weather conditions are ambient (outside) air temperature and the time of placement of the concrete. Ambient air temperature is the single biggest factor to consider when pouring during the winter months. Furthermore, it is the low temperature for any given day that is the determining factor in our decision to pour or not to pour. We do not like to see low temperatures below 15°F. Concrete test cylinders cured in cold weather laboratories under these conditions indicate that strength gain is severely limited at or below this temperature. The time of day that a concrete placement is made is also very important during the winter months. Concrete should be placed as early in the day as possible to benefit from rising ambient air temperatures and any potential solar gain that can be realized. It is through careful consideration of these two factors that Damiani Concrete Company Inc. formulates the mix design we will use, as well as, what protection practices will be required.
Mix designs vary for any given set of weather conditions. During the hot summer months, retarders are added to the concrete to slow down the curing rate of the concrete. During the winter months, accelerators are added to the concrete to speed up the curing rate of the concrete. Acceleration of the curing rate of concrete can be achieved in many different ways. The addition of calcium chloride, water reducing agents, increased cement quantities, higher quality cement or the use of non-chloride accelerators will all increase the curing rate of concrete. Additionally, all the materials that are used to make concrete are heated during the winter months.
One of the main ingredients of any concrete mix design is water since it is necessary to hydrate the cement particles, which in turn promotes strength development. While it is necessary to the mix design at prescribed levels, any additional water added on the site can be detrimental to the performance of the mix design. It’s simple, the more water that is added to the concrete over and above the specified levels the more likely it is to freeze and impede strength development. For this reason, Damiani Concrete Company Inc. adds no water to the mix on site. Instead, we add superplasticizer to the concrete to increase allowable slumps and enhance early strength development without increasing the likelihood of freezing. You could call it our “secret ingredient.”
Finally, once the mix design is chosen and the concrete is placed, the last step to insuring a successful pour is protecting the concrete. As was mentioned earlier, the materials used to manufacture concrete are heated during the winter months. Concrete temperatures at the time of placement are usually between 60° – 70°F. Additionally, as the concrete is curing, a hydration reaction is occurring which generates heat internally. Through the use of insulating straw and thermal blankets, as well as, formed air spaces we are able to maintain the internal temperatures of the concrete at levels that allow it to continue to gain strength. Protection is not always required, however, it is always better to be safe than sorry! Weather forecasts are not always correct as we in Buffalo know all too well.