Concrete Curing Temperature Makes a Difference

How Warm Does it Have To Be To Pour Concrete?

Whether the conditions are hot or freezing, the ideal concrete curing temperature should be maintained at about 55°F to achieve the optimum concrete strength.

Curing the Hoover Dam

At its completion in 1935, the Hoover Dam was the largest dam in the world and a marvel of labor and engineering.  The first pour began on June 6, 1933. Rather than being a single block of concrete, workers built the dam as a series of individual columns. The trapezoidal columns rose in five foot lifts. This method allowed the tremendous heat produced by the curing concrete to dissipate. If the dam were built in a single continuous pour, the concrete would have gotten so hot that it would have taken 125 years for the concrete to cool to ambient temperatures. The resulting stresses would have caused the dam to crack and crumble away.  

The heat and dryness of Nevada posed additional complex problems with the pour and concrete curing temperature.  When the concrete was first poured, river water circulated through cooling coils of 1″ thin-walled steel pipes. Once the concrete had received a first initial cooling, chilled water from a refrigeration plant on the lower cofferdam circulated through the coils to finish the cooling.

Concrete Curing is an Art

We live in a world where faster always seems better; however, concrete that cures too quickly or under hot concrete curing conditions can actually result in weak or unstable concrete.  If concrete is cured in cooler ambient  temperatures (32°F to 50°F) with moisture continually present, strength gain will be slow but the concrete will eventually reach a high strength. Concrete should not be allowed to get hotter than 90°F or to dry out during the curing period.

Best Concrete Curing Temperature

By “best” we mean “most thoroughly,” not the fastest.  High temperatures mean faster curing, but fast curing equates to weaker strength in the end.  The following study by Paul Klieger in the Portland Cement Association Research Bulletin 103 illustrates this concept.

concrete cure time chart with concrete curing temperature

Concrete Cure Time Chart with Temperature

At an age of 1 day the 120°F concrete was strongest and the 25°F concrete was weakest. By 7 days the high-temperature cured concretes had no more strength than the 73°F concrete or even less. By the age of 28 days the high-temperature concretes were weaker than the 73°F concrete. From 28 days to 1 year the 55°F concrete was considerably stronger than the 73°F concrete. All of this suggests that, provided there is continuous curing, concrete cured at about 55°F for the first 28 days ultimately reaches the highest strength (Concrete).

Hot Weather Concrete Temperature Limits

Hot weather concreting doesn’t simply involve temperature.  High ambient temperatures, winds, and relative humidity all play a role in “hot weather.”  Under hot heather conditions, the primary curing issue is having the top of the slab of concrete dry much faster than the bottom. As concrete dries it shrinks. This means that the top will be shrinking while the bottom is not. This creates internal problems with the concrete that will result in a damaged slab. The top and the bottom of the pour need to cure at the same rate (Placing).

Concrete Curing Temperature Solutions

Is it too HOT?

North Slope Chillers makes portable cooling equipment that will keep newly poured concrete safe from heat. Portable, insulated, and efficient, North Slope Chillers effectively regulates the temperature of concrete under both regular and hot conditions.

The Fluxwrap Circulation Blanket is combined with either a cooler or chiller to achieve optimum results. The Circulation Blanket draws heat to the blanket in order to cool the concrete.

  • Use Powerblanket’s patented heat-spreading technology in reverse–the cooling blanket draws heat away and lowers the temperature of the concrete.
  • Blanket cover and insulation are the same as the robust system used in Powerblanket heating products
  • Portable
  • Control the curing speed of newly poured concrete even in hot conditions

Is it too COLD?

Can you pour and cure concrete in the winter? Powerblanket concrete curing blankets provide a manageable way to cure concrete effectively and confidently in the cold weather months. Even in warm weather, Powerblanket curing blankets increase production by rapidly curing with consistent, even heat.

  •   Cure concrete 2.8 times faster than conventional, insulated blankets
  •   Produce cold weather concreting strength of up to 3,925 psi in 72 hours
  •   Maintain moisture throughout hydrating process
  •   Easily installed and removed
  •   Prevent a freeze cycle
  •   Thaw ground and frost from job site prior to pour
  •   Reduce downtime & increase profitability
  •   Maintain ACI compliance for cold weather concreting

Powerblanket understands what it’s like to work on large concrete projects when the weather and temperatures aren’t cooperating. From the Statue of Liberty to a major interstate bridge in Kansas City, we’ve been a part of the action and have proven our products to be the best in the industry.

For more info on solutions, check out Powerblanket’s Concrete Curing Blankets and find one that fits your needs best.

Works Cited

“Placing Concrete in hot or cold weather”. Sakrete Blog. 16 May 2017. http://www.sakrete.com/media-center/blog-detail.cfm/bp_alias/Placing-Concrete-in-hot-or-cold-weather

“The Story of Hoover Dam – Essays”. Bureau of Reclamation. 16 May 2017. https://www.usbr.gov/lc/hooverdam/history/essays/concrete.html

Learn More About Concrete Curing Blankets

How Long Does Concrete Take To Set?

If you really want to know the truth, concrete never stops curing; it continually hardens forever. However, for practical purposes, it reaches a point where further hardening will be so slow it becomes unnoticeable. In this article, we cover the basics of what you need to know if you’re asking the question, “how long does concrete take to set?”

Concrete Never Stops Curinghow long does it take concrete to set

The continual hardening occurs because cement particles react with the water in the mix (hydration), and as long as cement is in contact with moisture, even minuscule bubbles, it will continue to form bonds. This is minimal after “full strength” is achieved, but it is continual.

Curing Time for Concrete

In standard industrial cases, full strength concrete is recognized at 28 days. At seven days, you should have concrete that is cured to 70% full strength or greater. But to answer the question of, “How long does concrete take to set?” concrete setting time is generally 24 to 48 hours. At this point the neighborhood dog will not leave his footprints in it, but you should keep it clear of heavy equipment during this time period. Most mixes are cured at 28 days.

Factors Affecting Concrete Setting Time

  • Moisture's Effect on Concrete SettingMoisture plays a critical role in curing time for concrete. If there is not sufficient water in the mix, the concrete will cure too fast, resulting in weaker overall strength. Too much moisture, often used in the finishing step will weaken the top layer and cause flaking.
  • Hot ambient temperatures and wind accelerate the evaporation of moisture–speeding concrete setting time.
  • The mix design has a lot to do with concrete setting time. Some jobs will require accelerants because the area needs to be usable as soon as possible. The accelerant will do its job and speed up the concrete setting time. Accelerant mixes will show a weaker overall strength in the end, but will still meet strength requirements.

Temperature also has an impact on concrete setting time. For more information, check out this article about how concrete curing temperature makes a difference.

Concrete Blankets

If you are wondering about how long concrete takes to set, a solution for your concrete setting needs is a concrete heating or cooling blanket. But not all blankets are created equal. Consider the following two types of solutions to the effects of hot and cold:

The FluxWrap from North Slope Chillers is portable cooling equipment that will keep newly poured concrete safe from heat, regulating concrete setting time in both regular and hot conditions.

The FluxWrap is combined with either a cooler or chiller to achieve optimum results. The Circulation Blanket draws heat to the blanket in order to cool the concrete.

  • Use Powerblanket’s patented heat-spreading technology in reverse–the cooling blanket draws heat away and lowers the temperature of the concrete.
  • Take it with you on every job.  It is easily portable.
  • Blanket cover and insulation are the same as the robust system used in Powerblanket heating products
  • Control the curing speed of newly poured concrete even in hot conditions

If conditions are cold, concrete curing blankets provide a manageable way to cure concrete effectively and confidently. Powerblanket curing blankets increase production by rapidly curing with consistent, even heat.

  •  Cure concrete 2.8 times faster than conventional, insulated blankets
  •  Maintain moisture throughout hydrating process
  •  Easily installed and removed
  •  Produce cold weather concreting strength of up to 3,925 psi in 72 hours
  •  Prevent a freeze cycle
  •  Thaw ground and frost from job site before you pour
  •  Reduce downtime & increase profitability
  •  Maintain ACI compliance for cold weather concreting

 

Realize that just because you have a concrete curing blanket doesn’t mean you have a solution. The type of blanket and how that blanket is used will have a massive impact on your concrete. Read more about curing blankets here.

Learn More About Concrete Blankets