Best Practices for Mass Concrete Work in Hot Weather

Brief 

Contractors that need to place mass concrete in hot weather should prioritize nighttime placements and add ice, cooling water or liquid nitrogen to the concrete mix, write Sarah De Carufel and Keya Shirali from Giatec Scientific. They note that the maximum concrete temperature differential should not surpass 35 degrees Fahrenheit during curing

Insight

Summer can be the busiest time for the construction industry. Not only do the summer months provide the chance to get a lot done, but it also helps you avoid the challenges that come with cold weather concreting,

like the freezing of concrete at early stages. However, hot weather concreting places several risks to the strength and durability of your mass concrete pour if adequate measures and calculated precautions are not taken to cool your concrete during the curing process.

High ambient temperature, high concrete temperature, low relative humidity, and high wind speed—all of these are factors that could affect the quality of freshly mixed or hardened concrete which according to ACI 305.R10, could accelerate “the rate of moisture loss and rate of cement hydration, or otherwise [cause] detrimental results”.

Potential Problems When Pouring Concrete in Hot Weather
Increased temperature may result in a higher early hydration process potentially affecting the strength at later stages (i.e. 28 days) affecting the durability.

• The concrete may fail to hydrate properly due to the lack of the presence of water, which could lead to the loss of strength as well as cracking.
• Increased rate of setting, causing difficulty with handling, compacting, and finishing, and a greater risk of cold joints.
• Increased tendency for plastic shrinkage.
• Increased difficulty in controlling entrained air content.