Pouring a Concrete Slab in Hot Weather

It’s not a common phrase when it comes to the process of laying a concrete slab. Hot weather refers to temperatures that are above 90 degrees F as well as low relative humidity or high winds. The conditions are further described in the ACI chapter 305. It’s true it’s not just temperatures in the air. In certain regions, hot weather can occur any time of the year as a result of the humidity levels or the speed of the wind.

The problem with hot weather isn’t the heat that is generated when making a concrete slab, but the fact that concrete cures via the process of hydration. If the temperature of the concrete is greater than 77 degrees Fahrenheit, the process of the hydration process is speeded up and creates internal heat. When cement hydrates, it utilizes water and forms crystals around those aggregates. If the temperature is too high it can lose water by the process of evaporation. This makes it difficult for concrete to properly hydrate because of the absence of water and could cause weakening. The biggest issue with working in hot weather isn’t only the temperature of the air but also the temperature of concrete.

Concrete pouring in hot weather can create the following issues:

  • The difficulty is increased when you finish the concrete
  • The development of cold joints is caused by heat conditions that reduce the time for setting.
  • The strength and durability of the material is diminished.
  • Lower compress strength
  • Drying shrinkage in addition to the concrete hardened
  • Greater risk of cracking

When the temperatures in concrete during its concrete placement is greater than 77degF A plan must be designed to minimize the effect of high temperatures.

  1. You must have enough manpower to handle the concrete while it’s being poured as well as to finish the processit’s not just a single-person job.
  2. If you can, do not pour concrete in the afternoon or during periods of high temperature.
  3. Pouring concrete in hot weather, you should space joints with a smaller spacing than joints for cold weather.
  4. Utilize sunshades or windbreaks to limit the possibility of harsh weather.
  5. Make plans to have outdoor slabs laid after the walls and roofs have been constructed.
  6. Concrete is poured in hot weather , keep an Evaporative retarder available to be ready in the event that the temperature becomes more extreme and the water is disappearing.
  7. Make use of ice in your concrete’s water mixture to help cool the concrete.
  8. Reduce the mixing duration once water is included in the mix.
  9. Bags of concrete mix as well as all the equipment needed to pour concrete in hot weather must be kept covered or under shade until the very last minute before use.
  10. If you are pouring concrete to make a slab, it is best to first make sure to dampen the sub-grade.
  11. Utilize cool water moisten sides of slabs and walls.
  12. Use the proper curing procedure to let the concrete form uniformly.


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