Although concrete needs heat to set properly, you can still pour new concrete during winter in a northern climate by completing the right preparations and using concrete heating equipment. When you are pouring concrete this winter, here are some tips to help you complete the job successfully and avoid freeze damage.
Heat the Concrete Mix
When you are planning to pour concrete while the air temperature is predicted to be below 40 degrees F or below, you should consider using concrete cold weather guidelines to help protect your new concrete from the frost. The American Concrete Institution recommends to use cold-weather concreting guidelines specifically when more than three successive days will have an average daily temperature below 40 degrees F, and the temperature is going to stay below 50 degrees F for longer than 12 hours during any 24-hour period of these three days.
It is important to follow these guidelines when pouring concrete. When concrete cures, the water combines with the cement to create a chemical reaction in the mixture, causing the concrete to cure into a hard material. If the water in the concrete freezes, it cannot create the necessary chemical reaction and your concrete will flake and crumble.
The first step you can take with a cold-weather concrete job is to make sure your concrete mixture arrives heated from the mixing plant. This can help prevent your concrete from cooling too fast when it is poured. Most concrete mixing plant crews will take the outside temperature into consideration when preparing your concrete mixture, but it is always a good idea to double check with them.
Prepare the Area
The ground you are preparing to pour your concrete over in winter may be frozen. Cold ground can cool your concrete too quickly, causing your concrete to stop its curing process. So, along with setting your forms and spreading your base soil, you need to make sure to thaw and heat the ground where your concrete will be poured. The best way to do this is by using a hydronic heater, which pumps a heated liquid through loops of hoses set over the site on 12- or 24-inch centers. Then, spread a vapor barrier over the hoses to keep the moisture from escaping and drying out the area. Cover the vapor barrier with a concrete insulating blanket. The warmer the ground is, the warmer the concrete will remain so it can cure faster.
You can use a portable hydronic heater to thaw several feet into the ground. Most hydronic heaters will thaw the ground at a rate of one foot per day for the first three days, then one-half foot per day from day four and after. Plan to set up your hydronic heater several days before you will pour the concrete to allow enough time for the thawing process.
A hydronic heating system works more efficiently than an air heater, where only 15 percent of its heat penetrates into the ground and the rest escapes upward. Ninety-three percent of the heat from a hydronic heating system reaches and heats the ground.
Protect the Curing Concrete
Remove the insulating blanket, vapor barrier, and hydronic heating hoses to pour the concrete. Then, as soon as the concrete is poured and smoothed, replace the vapor barrier, followed by the heating hoses placed at 24-inch intervals, covered with the insulation blanket. These layers will keep your concrete warm during the curing process to prevent freezing.
Freezing during the concrete's curing process can reduce its strength by up to 50 percent. During the first 24 hours after the concrete is poured, it needs to reach a strength of at least 500 pounds per square inch before it will be safe from freeze damage.
Use these tips to help you successfully pour concrete in cold weather conditions. For more information, contact a company that specializes in truck mounted tank heaters to see what kind of supplies they can help you with.