Primer: Tips for Placing concrete in the Cold Temps

Brief 

Richard Hubbard III from Master Builders Solutions offers tips for placing concrete in colder weather. “Concrete temperature at the time of mixing is influenced by temperature, specific heat and quantity of its ingredients,” Hubbard writes.

Insight

Cold weather is rapidly approaching but, as a contractor, you may have project obligations to fulfill, regardless of the weather. In fact, you may be ordering, placing, and curing concrete in cold weather—an ambient environment that can have an unfavorable effect on the set time, strength development and overall durability of the concrete—if precautions are not employed.

Do you know what to do to ensure that concrete placed in this environment develops the correct strength and durability? The correct selection and use of concrete admixtures along with other steps can be an effective means in which to protect the quality and durability of the concrete. Follow these tips for a successful project in cold weather.

Before we continue, let’s talk about what constitutes “cold weather.” According to the American Concrete Institute (ACI) Committee 306, cold weather is defined “as a period when for more than three consecutive days the average daily air temperature is less than 40º F (5º C) and the air temperature is not greater than 50º F (10º C) for more than one-half of any 24-hour period.”

The average daily air temperature is the average of the highest and the lowest temperatures occurring during the period from midnight to midnight.

The setting time of concrete increases approximately one-third for each 10º F (5º C) reduction in temperature. Low temperatures slow down the hydration process and significantly retard concrete setting time, which results in reduced compressive strength at early ages, however, increased strength at later ages (see Figure 1).

Low temperatures can have a beneficial impact on the hardened concrete properties as recognized by ACI Committee 306 and in ACI 306R, “Cold Weather Concreting”, “one should take advantage of the opportunities provided by cold weather to place low-temperature concrete.

Concrete placed at low temperatures [40-55º F (5-13º C)], is protected against freezing and receives long-time curing develops a higher ultimate strength and greater durability. It is less prone to thermal cracking than comparable concrete place at higher temperatures.”