Defining Cold Weather Concrete

  • Daily Temp below 40F for more than 3 consecutive days
  • Average Daily Temperature- Average temperature over a 24-hour period
  • When air temperature has fallen to, or is expected to fall below 40F during the protection period
  • Protection Period is defined as the time recommended to prevent concrete from being adversely affected by exposure to cold weather during construction

Prevent damage to Concrete due to freezing at early ages

  • Assure that concrete develops the required strength for safe form removal
  • Early freezing can result in the loss of up to 50% of the intended strength
  • Must reach 500 psi in order to prevent damage from freezing
  • Pore water starts to freeze at 30 degrees
  • Water in the pores of the aggregate
  • At 25-27F degrees, enough pore water will freeze that hydration will stop
  • Hydration is the chemical reaction of cement with water which causes the hardening process to take effect
  • Below 27F degrees, the formation of ice may be detrimental to the long term integrity of the concrete

Cold Weather Protection Plan

  • 40F and rising temperatures
  • Temperature must be reached by 12:00 p.m.
  • If temperatures are expected to fall below 40F after the pour, insulated concrete curing blankets are required during the Protection Period
  • 33F to 39F temperatures
  • Temperature must be reached by 12:00 p.m.
  • 2% Calcium and/or other Curing Additives are required
  • Accelerates hydration process by chemical reaction
  • Reduce curing time
  • At 50 degrees, concrete with 2% calcium will cure at the same rate as plain concrete does at 70 degrees.
  • Increases workability
  • Concrete can be poured at a lower slump which results in less water in the mix which means less hydration needed to reach strength.
  • Concerns to using Additives
  • Can cause curing to happen too fast, causing cracking and loss of strength.
  • Who pays and situations (It depends: Who is driving the pour?)
  • Check with Thermometer to monitor concrete temperature
  • Clear a 3” area in all directions
  • Place Thermometer and pack concrete around it to stop ambient temp form altering the reading. Must remain in the concrete at least 2 min. and not more than 5 min.
  • Should remain above 60F
  • Keep covered with insulated concrete curing blankets during the Protection Period
  • Recommendation for pouring during these temperatures
  • Covering subgrade prior to pouring concrete
  • Maintain subgrade temperature
  • Pour Flatwork and/or Footings instead of a Slab
  • 32F OR BELOW DO NOT POUR