Temperature, humidity, and wind oh my!
In Kansas, we never know what we’re going to get (even in the same day!) Some days are ideal for pouring concrete and others—not so much. We typically have freezing days through April, so keep a close eye on those temps! Most weather conditions can be overcome with some prep (mentioned below) and a few precautions. If you’re brave enough to tackle this as a DIY project, check out these tips from Jeff so you are more than well prepared!
Freezing weather – To pour or not to pour?
The fact is, you’ve got to watch yourself on newly-poured concrete. A fresh pour should never be allowed to freeze within the first 24 hours. The freezing of the cement before it reaches a 500-pound strength per square inch, can cause irreparable damage. However, if the concrete sets properly in the first 24 hours, it is safe from freezing damage. So, if there’s even the slightest chance of the temps dropping below 32 degrees in the next day or so, just wait…you’ll be glad you did. Be patient and do it right!
Well, it’s not going to freeze. What about cold weather in general?
Ideally, concrete work should be done when the temperature is over 40 degrees. In the industry, “cold-weather concreting” is when, within 3 consecutive days, the average daily temperature is below 40 degrees and stays below 50 degrees for more than one-half of any 24-hour period. Cooler temperatures are great for strength but, in cold weather, the time it takes for the concrete to set up and add the finishing touches can vary depending on the type of concrete, the size of the pour, and use of the space.
Other precautions to protect a cold weather project:
- Windbreaks protect the concrete as well as the crew from cold winds that’s led to dropped temps and evaporation. Six feet is a sufficient height but can vary based on conditions
- Heated Enclosures are very effective for protection during cold-weather concreting but tend to be a very pricey option. Prefabricated enclosures can be purchased, and can be constructed out of wood, canvas tarps or polyethylene.
- Heaters can vary from direct/indirect fired, and hydronic systems, are also very useful during cold-weather concreting. Workers need to be extra cautious when using heaters in enclosed work areas to avoid carbon monoxide overexposure.
- Polyethylene Sheets or insulating blankets may be only required precautions in some instances, because cement produces heat on its own.
Moisture is very important in the curing process–so low humidity and heaters within enclosures may be a concern. We advise you to leave forms in place for as long as possible for even distribution of heat. Exhausting steam into an enclosure (which provides heat and moisture) is great for curing.
Once the concrete has set but not completely cured, it’s important to prevent sudden cooling, as thermal cracking may occur. Gradually remove the heat source and allow enclosure to stay in place to ensure proper cooling. Large structures may require one day to several weeks of gradual cooling to avoid cracking.
Don’t let the colder weather slow down your home projects!
Just make sure you are well prepared or select a trusted contractor so that your project looks good as new for many years to come.