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Published on 11/11/2019

Published by marketing@concretebroker.com.au

Tips for pouring concrete in hot weather

The main concern with working in hot weather isn’t just the air temperature, but the concrete’s temperature


 

Cover photo courtesy of : Photo by Laura Vinck on Unsplash

 

 

Tips for Pouring a Concrete Slab in Hot Weather

     
Source : Sakrete.com

 

 

 

Hot weather isn’t a general term when talking about pouring a concrete slab. Hot weather is defined as high ambient temperatures above 90°F, low relative humidity and/or high wind speeds. These conditions are further explained under ACI 305. That’s correct, hot weather isn’t just air temperature. In certain areas, hot weather can be anytime of the year because of humidity levels or wind speeds. 

The issue with hot weather isn’t really the heat when pouring a concrete slab because concrete cures through hydration. When the concrete is hotter than 77°F, the process of hydration is sped up and generates internal heat. When cement hydrates it uses water and grows crystals around the aggregate particles. When it's too hot, water can be lost through evaporation. This doesn’t allow the concrete to hydrate properly due to the lack of water present and can result in loss of strength. The main concern with working in hot weather isn’t just the air temperature, but the concrete’s temperature.

Pouring concrete in hot weather could present the following problems:

  • Increased difficulty when finishing the concrete 
  • The formation of cold joints due to hot weather decreasing the setting time
  • Reduced strength and durability
  • Lower compression strength 
  • Additional drying shrinkage of the hardened concrete
  • Increased risk of cracking

 

If the temperature of the concrete at the time of concrete placement will exceed 77°F, a plan should be developed to negate the effects of high temperatures.

  1. Have sufficient manpower to manage the concrete when it is being poured and for the finishing process ­— this is not a one-person job. 
  2. If possible, avoid pouring concrete at noon or during peak times for hot air temperature. 
  3. When pouring concrete in hot weather, space control joints at smaller intervals than cold weather concrete joints.
  4. Use sunshades or windbreaks to reduce possible harsh conditions.
  5. Plan to have indoor slabs poured after all walls and roofs are built.
  6. When pouring concrete in hot weather keep an evaporative retarder ready on site in case the temperature gets hotter and water is rapidly evaporating.
  7. Use ice as part of the concrete water mix to cool the concrete.
  8. Reduce the mixing time once water has been added to the mix.
  9. Bags of concrete mix and all equipment needed to pour concrete in hot weather should remain covered or in the shade until the last moment before using. 
  10. When pouring concrete for a slab, first dampen the sub-grade. 
  11. Use cool water to dampen side forms for slabs or walls.
  12. Implement the correct curing method to allow the concrete to set uniformly.

 

Need some help pouring a slab? Keep these tips in mind and watch this video.

 

 

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Tags: heat and concrete hydration pouring concrete weather


This article was written by marketing@concretebroker.com.au all rights reserved. The views and opinions expressed in this article are those of the author(s) and do not necessarily reflect those of concretebroker.com