You don’t need to wait for summer to start that concrete project
Whether it’s a new foundation, driveway, planned project, or emergency repairs, sometimes you need to learn to work with concrete in the cold. The good news is that pouring concrete in cold weather is not off the table, and there’s no need to wait for warmer temperatures to do concrete work as long as you know how. Follow these 10 tips before you start that concrete project in the wintertime.
According to the American Concrete Institute, an international authority on concrete best practices, special techniques are required when pouring concrete in cold weather, specifically temperatures below 50 degrees Fahrenheit. But there is an upside. When done correctly, concrete poured in cool weather can be stronger than concrete poured in hot weather because of the slower curing time.
So, yes, you can pour concrete in the winter. In fact, with the right materials and information, you can get the job done any time of the year. Read on to learn how.
Keep the weather in mind when pouring concrete. If it's too hot or cold outside, it can make the process more difficult. Try to pour concrete in 50 to 60 degree weather.
Pouring concrete in cold weather is possible and sometimes even preferred. But wait for warmer weather if temperatures have been or are expected to be too cold, especially if you’re pouring concrete in the rain. Aim for temperatures above 40 degrees Fahrenheit, and never pour concrete below 20 degrees Fahrenheit unless you’re an expert with experience in cold-weather concrete work. It can be nearly impossible to keep materials warm enough for proper curing in extreme cold. If the liquid concrete freezes before it cures, you risk permanently damaging and weakening the installation.
People always come first. When working in cold weather, it’s imperative to take care of yourself and the crews pouring the concrete. Try these tips:
Use warm clothes, heaters, warming stations, and regular breaks.
Know the signs of frostbite and hypothermia, and have a plan for staying and getting warm.
If you’re hiring a concrete contractor near you to do the work, ask about their cold-weather contingency plans for employees and the job. Hiring the best concrete contractor can take a little research, but it's worth the work in the end.
Understand that cold temperatures can mean longer cure times, which can mean longer timelines for job completion, higher labor costs, and increased concrete slab cost.
Never pour concrete on frozen ground, ice, or snow. Instead, assess air and ground temperatures and warm the ground by covering it with blankets or black plastic for a few days before the concrete work begins. If conditions are expected to be windy or evolving, consider constructing windbreaks to protect the site from wind and temperature changes. Very cold conditions may require protective enclosures and heaters. And remember to warm tools and forms. Cold forms and tools can cool the concrete too quickly, so store them inside or warm them before use.
It’s very important to use concrete that’s compatible with cool-weather pouring. You’ll want to choose a strong type of concrete that has a compressive strength rating of 4,000 pounds per square inch or 27 megapascals. You can also look for air-entrained concrete that allows water into tiny voids, which relieves pressure during freezing and expansion.
If you’re hiring a concrete contractor, verify that they’re using concrete recommended for cold weather, and have them put the specifics in writing in your contract.
Curing times are longer when pouring concrete in cold weather, but the faster the concrete sets, the less likely it is to fail due to cold weather damage. To make concrete cure faster in cold weather, experts recommend using accelerants, also called accelerating chemical admixtures, and water reducers.
You can also adjust the concrete mixture to better perform in cold temperatures. Adding more cement can bring the mix to optimal hydration levels and add more heat to the curing process, which can make curing go faster and result in stronger concrete that resists cracking, chipping, and concrete spalling.
Preheating the water and aggregate mix to between 140 and 180 degrees Fahrenheit is a smart way to get the right pouring temperature. Transporting ready-mixed concrete in warmed trucks and keeping concrete that’s mixed on-site in a warm location are also smart moves. Then, pour it as soon as you can so it’s as warm as possible when placed, and be ready to keep it warm while it sets.
During curing, use an infrared temperature gun to monitor temperatures. Concrete should ideally stay above 50 degrees Fahrenheit and shouldn’t fall below 40 degrees Fahrenheit during curing, and it should never be allowed to freeze during the first 24 hours after pouring.
If you’re pouring in an enclosed area, use heaters or insulating blankets to keep the concrete warm as it dries. It’s smart to keep a log of air and concrete temperatures during cooling so you can anticipate trends. Even if you don’t think you’ll need them, have blankets, lights, and heating options ready in case the temperature drops too fast.
Don’t rush the curing process. All the bleed water should evaporate before the finishing process begins. Because cold-weather curing takes longer, the bleed process will begin later and take longer than usual, and more water may bleed from the concrete. This process takes even longer when pouring concrete in the rain, so give it all the time it needs based on conditions.
Keep concrete forming equipment in place as long as possible when pouring concrete in cold weather. Forms help retain heat and prevent the concrete from drying too fast. In very cool conditions, consider using heated forms or pumping steam in the pour area. Because concrete poured and set in cold weather cures more slowly than concrete poured in warm weather, plan to give it several days to weeks for gradual curing, depending on the temperature and size of the job, to prevent cracking or other common issues such as concrete popouts.
Once the concrete has cured completely, apply a sealant to keep water from seeping back in. If you’re in an extremely cold area, choose a breathable sealant so water can evaporate from the concrete slab. The cost to seal concrete and recommended sealants depend on the job.
Lauren Bongard contributed to this piece.
