Cold Weather Concrete – Information and Best Practices
1/31/2023
 Cold Weather Objectives…
o Protect freshly placed concrete from early-age freezing – will expand
o Concrete strength development – must keep heat when curing
o Prevent thermal shock and cracking – must not shock concrete when removing heat
 What is the definition of cold weather? Several
o ACI 306R (before 2010) – Period when, for more than 3 consecutive days
 Average daily air temperature is less than 40℉, and…
 Air temperature is not greater than 50℉ for more than ½ of any 24- hr. period
o ACI 306R 2010 & 2016 – When air temperatures has fallen to, or is expected to fall
below, 40℉ during the protection period.
 Water in concrete does not freeze at 32℉; water in concrete freezes at 28℉
 As water freezes, it expands 9%
o Critical degree of saturation is 91.7%
o So, if the voids in the concrete are 91.7% filled with water and it freezes the voids are
100% filled with ice. If there is more water, the ice will damage the concrete.
 We must protect the concrete until the degree of saturation is 91.7%
 The degree of saturation will drop below 91.7% once the concrete reaches approximately 500
psi compressive strength
o At 50℉, most concrete will reach 500psi during the second day. Must protect fresh
concrete from freezing for at least two days to avoid expansive ice pressures. But as the
temperature drops, setting or hardening time is delayed.
 For every 10℉ drop, set time is extended by 1/3
 Cold weather extends the window of finishability for contractors.
o Contractor and field team to take this delay into consideration
 Request contract partner to provide a cold weather concreting plan to Haskell during the bid
process
 Use cold-weather concrete mix designs when placing concrete in cold conditions – reduces time
of protection, generates hydration heat for curing, offsets delayed finishing and strength gain
o Use Type III Cement
o Add additional Portland Cement
o Chemical Admixtures – accelerators
o Hot water
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Minimum Place and Mix Temperatures – do not exceed minimum placement
temperatures by more than 20℉
Section Size (minimum dimension)
Air Temperature
Less Than 12”
12” to 36”
36” to 72”
Minimum Placing and Curing Concrete
55℉
50℉
45℉
Minimum Concrete Mix Temperature
Above 30℉
60℉
55℉
50℉
0 to 30℉
65℉
60℉
55℉
Below 0℉
70℉
65℉
60℉
 Before concreting
o Surface Temperature
 Formwork (metal) – above 10℉
 Subgrade/base material in contact with slab on grade - 32℉
 The temperature difference of the subgrade and fresh concrete should
be no greater than 20℉
 Most embeds, including rebar, do not require heating unless air temperature is
less than 10℉
 Embeds with cross-sectional area larger than 4 square inches must have a
minimum temperature of 32℉
o The engineer should identify the minimum temperatures in the specifications
o Remove all snow, ice, and frost
o Do not place concrete on frozen subgrade
 Heating systems
o Glycol systems – to heat subgrade
o Blankets – to hold curing temperatures
 Must not damage finish
 Must be secured
o Heated enclosures
 Must not use direct fired heaters on new slab. CO2 emissions will cause weak
surface of slab
 Cold Weather Concrete Tips
o Know and understand specified cold weather concreting requirements
o Use cold weather mix design
o Plan ahead for protection
o Protect from early age freezing
o Protect corners, edges, and surfaces
o Anticipate delayed setting and finishing problems
o Do not expose new concrete to repeated freeze/thaw cycles until strength reaches
3,500psi
o Do not expose new concrete to deicing chemicals until 30-day air dried