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As an example, a concrete mixture that reaches final set in three hours at 60 degrees Fahrenheit may reach final set in as little 1½ hours at 80 degrees Fahrenheit. Setting Time The effect of high ambient temperatures and high temperature concrete component materials have on the setting time of concrete mixtures is a topic of concern due to the reduced time in which concrete must be placed, consolidated and finished increased potential for plastic shrinkage cracking, thermal cracking and cold joints potential strength reduction due to high water demand and high curing temperatures difficulty in controlling air content and increased urgency for applying appropriate curing method at an early age.Īs a general rule of thumb an increase of 20 degrees Fahrenheit will reduce the setting time of a concrete mixture by as much as 50 percent. With proper planning and execution concrete can be successfully placed and finished to produce high quality durable concrete at temperatures of 95 degrees Fahrenheit or more. In extreme conditions consider adjusting the time of concrete placement to take advantage of cooler temperatures, such as early morning or night time placement.

Provide appropriate curing methods as soon as possible after the concrete finishing processes have been completed.Consider fogging the area above the concrete placement to raise the relative humidity and satisfy moisture demand of the ambient air.Provide sufficient labor to minimize the time required to place and finish the concrete, as hot weather conditions substantially shorted the times to initial and final set.

Protect the concrete surface during placement with plastic sheeting or evaporation retarders to maintain the initial moisture in the concrete mixture.

Use a concrete consistency that allows rapid placement and consolidation.

The effect of hot cement on concrete temperature is only minimal.

Cool aggregates and mixing water added to the concrete mixture to reduce its initial temperature.

Erect temporary wind breaks to limit wind velocities and sunshades to reduce concrete surface temperatures.

Moisten subgrade, steel reinforcement, and form work prior to concrete placement.

The precautions may include some or all of the following: In general, if the temperature at the time of concrete placement will exceed 77 degrees Fahrenheit a plan should be developed to negate the effects of high temperatures. The precautions required to ensure a quality end product will vary depending on the actual conditions during concrete placement and the specific application for which the concrete will be used.