ICFs and Cold Weather Concrete Series
December 3rd, 2009 | From the Field, Lets Get Technical!
Since we are heading into the winter months now, we receive stories and pictures from guys in the field on how wonderful it is to build with ICFs during the winter months. If certain precautions are taken when building with insulating concrete forms (ICFs), concrete can be placed properly throughout the winter months even in cold climates.
ACI 306 is the standard used for placing concrete in cold weather. ACI 306 defines cold weather as a period when for more than 3 successive days the mean daily temperature drops below 40º Fahrenheit (F). Normal concreting can resume once the ambient temperature is above 50º F for more than half a day. Fresh concrete that begins to freeze can reduce the strength gain and its durability.
The next few posts in this series will look a cold weather concreting form a technical standpoint, showing pictures and proejct examples in the field, and will highlight the extra steps needed to do CMU construction during cold weather.
Cold Weather Concreting
The concrete mixture and its temperature must be adapted to the construction procedure during cold weather. This means making preparations to protect the concrete’s temperature from the cold air. The insulating concrete forms, reinforcing steel and concrete embedments must be clear of snow and ice when the concrete is placed.
Concrete strength gain is a function of the temperature at which it cures. Typical concrete compressive strengths are based upon the concrete curing at an ideal temperature of 72º F the entire 28 days. Temperatures higher than 72º F will shorten the curing time and temperatures lower than 72º F will increase the curing time. Concrete gains very little strength at low temperatures.
The concrete must be protected against freezing effects until the degree of saturation of the concrete has been sufficiently reduced by the process of hydration. This time corresponds to the time that it takes the concrete to attain a compressive strength of 500 psi. During normal temperatures, this time is usually within the first 24 hours of concrete placement. Significant strength loss of up to 50% can occur if concrete is frozen shortly after placement or before it reaches a strength of 500 psi.
Yes that it snow, not a white sand beach. This is an Air Force Base Reward did a few years ago in Alaska.
For Tuesday we will talk about the chemical reactions and properties of concrete that play a role curing concrete in cold weather.
