ICFs and Cold Weather Concrete Part III
December 10th, 2009 | From the Field, Lets Get Technical!
So far we have discussed the basics of using insulating concrete forms in cold weather, as well as broke down the main reactions and ideal temperatures for concrete to cure properly. Now we’ll go over how the insulating properties effect the minimum temperature concrete can be placed at. Also we’ll summarize some tips to result in strong concrete during cold weather.
Insulating Concrete Forms in sub-freezing temperatures
In order to keep the concrete at the desired temperature for the protection period, the concrete must be covered or insulated. This is where ICF construction in cold climates becomes an obvious benefit. The R-value of one panel of Reward iForm EPS is R-10. Assuming a cement content of 500 pounds per cubic yard and a wall thickness of 6 inches and interpolating from the graph below for R-10, the minimum ambient temperature for placing concrete would be around 10º F.
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Thermal resistance (R) of insulation required to maintain the concrete surface temperature of walls and slabs aboveground at 50º F or above for 3 days. Concrete temperature as placed 50º F. Maximum wind velocity: 15 mph.
Thermal resistance (R) of insulation required to maintain the concrete surface temperature of walls and slabs aboveground at 50º F or above for 3 days. Concrete temperature as placed 50º F. Maximum wind velocity: 15 mph.
Insulating Concrete Forms
Using ICF construction in cold weather means that vulnerable corners and edges are consistently covered and protected. Forms are left in place to keep moisture and heat contained for an extended period of time, improving the curing condition of the concrete. Additionally, the consistent insulation from ICFs allows for even heat distribution.
Not only is it important to insulate the top of the Reward ICF wall after concrete placement in cold weather, there are three other areas to be concerned with. These include footings, bulkheads and embedment steel. Placing concrete on top of a cold footing and around cold steel embedments can affect the concrete temperatures in those local areas. Precautions should be considered or taken for these areas. Bulkheads, much like the top of the ICF wall must be insulated as well.
Tips for strong concrete
• Keep forms covered before concrete placement if any precipitation is expected. This will prevent snow and ice from forming inside the cavity of the ICFs.
• Cover the top course after concrete placement in order to contain the heat produced and to insulate the top of the concrete wall. Rigid or batt insulation blankets of R-10 or greater work well for both covering the forms before concrete placement and for insulating the top of the wall after concrete placement.
• Work closely with a local ready mix supplier to determine concrete mix requirements for the specific project and climate.
• Do not rush a concrete pour late in the day or if bad weather is approaching. This can lead to problems.
CMU vs. ICFs during Cold Weather
Next week we will highlight a specific ICF school job we were at about a week ago, where they used CMU for a portion of the building and ICFs for the other. The pictures will tell the story.
insulating concrete forms
