Winter is approaching, and with it comes the need to adapt construction practices to colder conditions. This year, our region is expected to experience another mild winter, with below-average snowfall and above-average temperatures, according to meteorologists. Snowfall is estimated at around 14 to 20 inches in Philadelphia, with two major storms potentially dumping six or more inches of snow each time. Average winter temperatures are so far forecast between 28 and 45 degrees Fahrenheit, with January likely to be the coldest month.
Even in a relatively mild winter, placing concrete can be challenging when temperatures consistently drop to 40 degrees or below. Concrete sets slowly during cooler temperatures, and if freshly placed concrete freezes before reaching a minimum strength of 500 psi, it could lose up to half of its ultimate strength. However, with proper techniques and precautions, successful cold-weather concreting is achievable.
The goal is to keep concrete at a minimum temperature of 50 degrees Fahrenheit until it reaches 500 psi. At this point, it can handle the cold on its own. Here are eight effective strategies for concreting in cold weather:
1. Consult with your ready mixed producer
Your concrete supplier can adjust mix designs to meet cold-weather needs, such as increasing cement content, adding chemical admixtures to accelerate set time and using air-entrainment to reduce water bleeding and improve freeze-thaw durability. Additionally, aim to place concrete at the lowest practical slump to reduce water content and associated freezing risks.
2. Heat mix materials
Heating materials like water and aggregates (but not the cement itself) can help maintain mix temperatures. Your ready mixed producer often handles this preparation to ensure the concrete arrives warm for placement (see Tip 1).
3. Use concrete pumps
Concrete pumping techniques speed up the placement process and reduce the time during which concrete is exposed to potentially freezing air, helping to maintain its temperature and workability. (For those considering renting concrete pumping equipment, Madison offers rental services for your daily concrete needs!)
4. Cover concrete with insulating blankets or plastic sheeting
Use plastic sheets or insulating blankets during curing to trap heat and moisture within the concrete. This is especially important at edges and corners, where triple-layer protection may be necessary to avoid uneven cooling.
5. Employ windbreaks, tents & supplementary heat
When conditions are too severe, set up windbreaks or enclosures (tents) to shield concrete from cold blasts. Use these enclosures alongside heaters to keep surrounding surfaces and air warm. Ground heaters also may be needed to thaw frozen ground before pouring.
6. Apply cure-and-seal products
Spray concrete with solvent-based curing compounds or cure-and-seal chemicals to avoid freezing. These products enhance moisture retention while offering a shield against harsh temperatures.
7. Leave forms in place longer
To ensure even heat distribution and prevent drying of concrete, leave forms in place for as long as possible during curing. This practice can prevent rapid cooling and moisture loss, which could damage the concrete.
8. Remove heat gradually
Avoid cooling fresh concrete too quickly, which can result in cracking. Gradually reduce heat by loosening forms while concrete is still covered, tapering off artificial heat within enclosures or turning off the heat and allowing the enclosure to slowly equilibrate to ambient temperatures. Massive structures may require several days or even weeks of gradual cooling.
Stay Ahead of Winter
While concreting in cold weather can present challenges, these precautions make it possible to maintain strength and durability even in tougher conditions. Whether you're dealing with unexpected cold snaps or January's chilly lows, keeping concrete at optimal temperatures remains the priority.
Reach out to Madison Concrete for assistance or guidance on your next cold-weather project. With our expertise, we’ll help you ensure success no matter what winter brings this season.