Hot Weather Concreting Made Easier

ARTICLE AT-A-GLANCE

How Can You Effectively Manage Concrete Placement in Hot Weather?

To effectively manage concrete placement in hot weather, ensure proper mix design adjustments, such as using low-heat-of-hydration cement and hydration-retarding admixtures, keep concrete temperatures below 90°F with chilled water or ice, limit time between mixing and placement, and use cooling solutions like Powerblanket ICE to maintain quality and prevent rapid moisture loss.

Key Takeaways

  • Understand the Impact of Heat: High temperatures accelerate evaporation and setting times, leading to potential slump loss and reduced ultimate strength in concrete.
  • Optimize Mix Design: Use low-heat-of-hydration cement and hydration-retarding admixtures to counteract the effects of heat, ensuring a more stable curing process.
  • Implement Cooling Techniques: Keep concrete temperatures below 90°F by using chilled water or ice, and consider scheduling pours during cooler parts of the day.
  • Adopt Protective Measures: Utilize wind screens and water misting to minimize surface moisture loss, and employ concrete cooling blankets like Powerblanket ICE for effective temperature regulation.
  • Follow Industry Standards: Adhere to guidelines from authoritative sources such as ACI 305R to maintain concrete quality and longevity in hot weather conditions.

Hot Weather ConcretingHot weather concreting

Hot weather concreting problems are most often encountered in the summer; however, any condition that increases curing rates and strips the concrete of moisture is considered hot weather concreting.

Pouring Concrete in Hot Weather

With temperatures rising and summer approaching, attentions shift from protecting concrete from the cold to concreting in hot conditions.  When pouring concrete in hot weather, special procedures should be followed for proper mixing, placing, finishing, and curing.  High ambient temperatures, high concrete temperatures, low relative humidity, and/or high winds impair the quality of freshly mixed and recently placed concrete (Hot).  Pouring concrete in hot weather affects laboratory test results, showing that higher temperatures affect the compressive strength gain of hardened concrete. Even though concrete poured in hot weather will produce higher early strength but as time goes by, the ultimate strength will be lower than expected (Rodriguez).

Water Loss

Hot weather concreting causes increased setting rates and rapid water loss.  Shrinkage and cracking are usually associated with hot windy weather.   The major side effect of faster curing and water loss is decreased overall concrete strength.  It is critical to prevent moisture from evaporating from the concrete surface. The evaporation rate removes surface water necessary for hydration , and thermal cracking may result from rapid changes in temperature, ie. pouring concrete on a hot day followed by a cool night (CIP 12). Proper mix design can compensate for these conditions, and in combination with protective measures to prevent rapid evaporation, quality concrete can be poured in hot temperatures (Rodriquez).

Adding water can increase concrete workability. However, adding water beyond the amount required by the approved mix design increases the water to cement ratio. This, in turn, can result in decreased compressive strength and an increased chance of cracking (Hot).

Recommendations for Hot Weather Concreting

Preparation is key and there are several basic precautions that can reduce the damaging effects of hot weather on concrete:

  • Use mix designs that are less susceptible to the effects of hot weather. The use of low-heat-of-hydration cement and certain admixtures (such as hydration retarding and/or water-reducing admixtures) are two standard approaches.
  • Keep concrete as cool as reasonably possible. ACI 305R does not state a maximum “as-placed” or “as-delivered” concrete temperature, but 90° F is commonly used. Substituting chilled water or shaved ice for a portion of the required mix water can help.
  • Limit the amount of time between loading the concrete at the plant and placement/finishing at the site.
  • Limit water addition at the job site, except to adjust slump upon arrival (when permitted by mix design).
  • Avoid or limit hydration accelerating admixture use.
  • Schedule large concrete pours in the early morning or evening when temperatures are cooler and have the manpower available to complete the job as quickly as possible.
  • Use temporary wind screens and water misting nozzles to reduce surface moisture loss (Hot).
  • Consider using a concrete cooling blanket to both retain moisture and protect the concrete’s surface from high ambient temperatures.

Powerblanket ICE Concrete Cooling

Powerblanket ICE® is portable cooling equipment that will keep newly poured concrete safe from heat.  Portable, insulated, and efficient, Powerblanket ICE effectively regulates the temperature of concrete under both regular and hot conditions.

The Powerblanket Ice Circulation Blanket is combined with either a cooler or chiller to achieve optimum results. The Circulation Blanket draws heat to the blanket while also cooling the concrete.

  • Blankets use Powerblanket’s patented heat-spreading technology in reverse–the cooling blanket draws heat away from the drum and lowers the temperature of the concrete.
  • Blanket cover and insulation are the same as the robust system used in the Powerblanket heating products
  • Powerblanket Ice industrial cooling systems are portable (120VAC required)
  • Control the curing speed of newly poured concrete even in hot conditions

 

Works Cited

“CIP 12 Hot Weather Concreting”. NRMCA. 5 May 2017. https://www.nrmca.org/

“Hot Weather Concrete”. Engineering Consulting Services.  5 May 2017. https://www.ecslimited.com/blog/hot-weather-concrete

Rodriguez, Juan. “Pouring Concrete in Hot Weather: Tips and Tricks”. The Balance.  5 May 2017. 

https://www.thebalancesmb.com/pouring-concrete-in-hot-weather-845030

 

Frequently Asked Questions

At what temperature is it too hot to pour concrete?

Concrete is best poured when temperatures are between 70° to 80°F; issues arise as temperatures approach 90°F, leading to rapid moisture loss and reduced strength.

What is too hot to cure concrete?

Concrete should ideally be cured at around 23°C (73°F), with 35°C (95°F) being the maximum allowable temperature for field placement to prevent accelerated chemical reactions and strength loss.

What are the rules for hot weather concrete?

The temperature of concrete at placement should not exceed 90°F to avoid accelerated setting, excessive slump loss, and increased water demand, which can compromise the concrete's integrity.

Is concrete good for a hot climate?

Concrete is beneficial in hot climates due to its thermal mass, which helps regulate indoor temperatures by retaining heat during the day and releasing it at night, making it suitable for regions with temperature fluctuations.

Cure your concrete faster and better in cold weather conditions with Powerblanket.


TITLE

Shelby Thompson

Shelby Thompson is the head of standard product sales for Powerblanket. He has a distinguished military career, having served in both Afghanistan and Iraq. In his time in the Marines, Shelby acquired an impressive skillset that he now uses in his current role. When he's not working, Shelby loves spending time outdoors with his wife, son, and daughter. He is also a semi-keen hunter, fair weather fisherman, and shooter. Unfortunately, Shelby also has something of an unlucky streak when it comes to Fantasy Football at the company.


Leave a Reply

Your email address will not be published. Required fields are marked *

preloader