With the construction industry operating year-round, concrete is poured and placed no matter the time of year. Although concrete can be placed in cold weather, certain precautions should be taken to ensure the job is handled properly. Take a look at the following five mistakes you want to avoid when pouring concrete in cold weather.
MISTAKE #1: PLACING ON FROZEN GROUND
If the ground is frozen or covered with ice or snow, you should not place your concrete. Frozen ground will settle as it thaws, which leaves your concrete susceptible to cracking. In addition, when wet concrete is placed on a cold surface, the concrete will set more slowly. This, too, can create cracking or scaling in the concrete.
Ozinga’s OzFlat-W, part of our OzFlat Series, is specially formulated for winter pours. This proprietary mix includes extra cement that provides a faster set time to help with early-age strength development and minimize issues related to overnight freezing temperatures.
MISTAKE #2: ALLOWING CONCRETE TO FREEZE
Plastic concrete freezes at about 25° F and doing so can reduce its final strength by more than 50%. Therefore, it is important to keep fresh concrete from freezing until it reaches a compressive strength of at least 500 PSI.
It is very important to protect the concrete and keep it as warm as possible (at least 50° F). This can be accomplished with insulating blankets or heaters.
A non-chloride or liquid chloride admixture can also help. Colder temps slow down concrete set times, but non-chloride admixtures can ensure your concrete sets at the normal rate. Liquid chloride is also an excellent accelerator for concrete, helping your flatwork set faster while improving workability and finishability.
Don’t use a liquid chloride accelerator if your flatwork will contain steel or another metal reinforcement, as liquid chloride can be corrosive to metals.
MISTAKE #3: IMPROPERLY USING HEATERS
In order to keep concrete at least 50° F, it’s a good idea to use heaters. However, if you use these heaters or heated enclosures incorrectly, you could cause a large amount of damage. For instance, if you’re using a fuel-fired heater, be sure that it is properly ventilated.
If not, the carbon dioxide given off in the exhaust can create a chemical reaction called carbonation, which can cause the surface of the concrete to become weak and dusty.
MISTAKE #4: MISJUDGING DAYLIGHT
During the winter months, daylight seems to leave as quickly as it appears. If you are running behind schedule, you could end up losing out on the daylight you need to complete the job. Always be sure to try and schedule your concrete pours during the day.
Not only does this give you an ample amount of light, but it also allows for a warmer temperature. If you will be forced to place concrete before the sun rises or after it sets, be sure you have plenty of lights and heaters on hand.
MISTAKE #5: SEALING WHEN IT’S TOO COLD
Most concrete contractors will either seal the concrete after the curing process or will recommend sealing to the customer. While sealing concrete offers plenty of benefits, it shouldn’t be done if the temperature is less than 50 degrees Fahrenheit. If you are placing concrete in cold weather, be sure to follow the manufacturer’s recommendations before sealing.
Ozinga has experience pouring concrete in different weather conditions. If you are interested in pouring when the temperature has dropped, talk to one of our concrete specialists first and ask about OzFlat-W for those colder weather flatwork pours.
