It’s not every day that you see work crews pouring concrete during the winter. The cold temperatures pose plenty of unique challenges for a successful pour, which is why it’s usually best to wait for warmer weather. However, there are times when you can’t afford to wait, as doing so could cost you both time and money.
To ensure that you get the same quality results as you’d expect in warmer weather, it’s important to not only understand these challenges but also how to overcome them. The following offers a few pointers you can use for a successful pour.
Challenges to Expect
Cold temperatures can drastically slow down the curing process. Below 50 degrees Fahrenheit, the curing process slows to a crawl, resulting in significantly longer set times. Below 40 degrees, the hydration reactions in concrete cease, preventing the concrete from gaining strength.
Another problem with pouring concrete in cold weather is that it can freeze before it has a chance to cure properly. This can result in the underlying matrix being broken up, which in turn makes the concrete much weaker than before.
Precautions to Take
Before you get started on your wintertime concrete pour, it’s a good idea to consider the following precautions:
- Never pour concrete on frozen or snow-covered ground. The frozen ground can settle once it thaws, putting the concrete at risk of developing stress cracks. In addition, contact with the frozen ground slows down the curing process, leaving the underlying concrete weakened.
- Request your ready mix producer to use air entrained concrete. This concrete contains numerous air pockets that allow water to safely expand as it freezes without adding stress to the concrete.
- Consider having the ready mix producer add extra cement to the concrete mix for a hotter exothermic reaction.
- Use concrete accelerators such as calcium chloride to speed up the hydration reaction and keep set times on schedule.
What to Avoid
During the winter, certain additives and materials can make an otherwise successful wintertime pour into a miserable experience. Take fly ash and slag cement, for instance. Although there’s nothing wrong with using these materials during warmer weather, cold outdoor temperatures can cripple their ability to set properly, resulting in lower internal temperatures and slower setting times.
The same goes for water reducers. Helpful for preventing slump loss in warmer temperatures, these chemicals can also slow down the set time when used in cold weather.
Talk to a concrete supplier like Island Ready-Mix Concrete for more information.