TO USE OR NOT TO USE AIR-ENTRAINED CONCRETE Often the heat from hydration along with covering the concrete with curing or insulating blankets is enough to cure the concrete and keep it from freezing. Heat of hydration is very important when pouring concrete in the winter. The amount of heat generated is affected by: The heat generated from this process is called heat of hydration. Once the dry ingredients (cement, sand, aggregate) are mixed with water a chemical process takes place between the cement and water where they form a paste. Low temperatures greatly slow the rate at which hydration of cement occurs which ultimately slows the hardening and strength gain of the concrete.Air-entrained concrete is less susceptible to early freezing than non-air-entrained concrete.Fresh concrete that freezes will not be as weather resistant or water-tight as concrete that hasn't been frozen.Concrete that goes through just one freeze cycle before reaching 500 psi may be restored to nearly normal strength if proper insulating/curing is done.Significant overall reductions in strength gain, up to 50%, can occur if concrete is frozen before it reaches 500 psi.At 40 degrees F concrete could take up to 3 days to reach 500 psi.At normal temperatures (70 degrees F) concrete usually reaches 500 psi in the first 24 hours.Freshly mixed concrete must be protected against freezing until it reaches a compressive strength of 500 psi.Concrete gains very little early strength at low temperatures.Fresh or Plastic concrete will freeze if the temperature falls below 25 degrees F (-4C).If the air temperatures are in the 30's F or below and the ready-mix company isn't using warm/hot water to batch the concrete, I would seriously think twice about pouring concrete that day.ĭid you know this about cold weather concrete?
PSI DROP COLD WEATHER CALCULATOR PORTABLE
I'm speaking from my own experience, actually checking the temperature of concrete mixtures when the concrete truck shows up on my job-site.įorms, rebar, and embedded bond-outs should all be clear of snow and ice before pouring or you'll have voids in those places.Īfter the concrete is placed, building enclosures, portable heaters, and insulated blankets should be ready to maintain the concrete temperature. Generally speaking, water temps between 120 - 140 degrees F will give you a concrete temperature around 60 - 70 degrees after it's mixed in the concrete truck. In cold weather, especially temperatures below freezing, the concrete mix should be batched with warm or hot water. NEVER pour on frozen ground, Never! Sorry, just wanted to make that clear. I've had concrete floors where the entire surface has peeled off (top 1/8") because the general contractor refused to protect and insulate the concrete after we troweled it and the temperature dropped into the 20's overnight. Protect the sub-grade and the concrete from freezing The air temperatures for the next four days were all below freezing but the slab temperature under the blankets four days after the pour was 70 degrees F. We covered the slab below with insulating blankets, a layer of hay, and a tarp over everything after we were done troweling. Let me teach you the right way to pour concrete in cold weather. One thing I know for sure, if you let newly poured concrete freeze, you will have issues with the surface scaling, pop-outs, cracking, and overall weaker concrete. Having to make a living pouring concrete floors during Maine winters since the 1980's, I've learned a lot about what happens to fresh concrete if it's exposed to cold and freezing temperatures. So, if you're wondering if pouring concrete is possible in cold weather- the answer is YES. Being from Maine, our cold weather concreting season is from late October until sometime in March. I experience brutally cold weather for about 5 out of 12 months a year here. Hello everyone, my name is Mike Day and I am the owner of Day's Concrete Floors, located in Maine. What happens to concrete when temperatures are below freezing?
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