Hot Weather Concreting
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Things to Consider about Hot Weather Concreting
When the temperature of freshly mixed concrete approaches approximately
25°C (77°F) adverse site conditions can adversely impact
the quality of concrete. Ambient temperatures above 32°C (90°F)
and the lack of a protected environment for concrete placement and
finishing (enclosed building) can contribute to difficulty in producing
quality concrete.
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| The use of liquid nitrogen is one option to
reduce concrete’s temperature during hot-weather concreting. |
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. In
general, if the temperature at the time of concrete placement will
exceed 25°C (77°F) a plan should be developed to negate
the effects of high temperatures.
The precautions may include some or all of the following:
- Moisten subgrade, steel reinforcement, and form work prior
to concrete placement.
- Erect temporary wind breaks to limit wind velocities and sunshades
to reduce concrete surface temperatures.
- Cool aggregates and mixing water added to the concrete mixture
to reduce its initial temperature. The
effect of hot cement on concrete temperature is only minimal.
- Use a concrete consistency that allows rapid placement and
consolidation.
- Protect the concrete surface during placement with plastic
sheeting or evaporation retarders to maintain the initial moisture
in the concrete mixture.
- 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.
- Consider fogging the area above the concrete placement to raise
the relative humidity and satisfy moisture demand of the ambient
air.
- Provide appropriate curing methods as soon as possible after
the concrete finishing processes have been completed.
- In extreme conditions consider adjusting the time of concrete
placement to take advantage of cooler temperatures, such as early
morning or night time placement.
With proper planning and execution concrete can be successfully
placed and finished to produce high quality durable concrete at
temperatures of 35°C (95°F) or more.
Additional information is available in the following references:
Hot Weather Concreting,
IS014.05, reprinted from Chapter 13 of Design and Control of Concrete
Mixtures, EB001.14, Portland Cement Association, 2002, 12 pages.
Hot and Cold Weather
Concreting, CD057, Portland Cement Association, 2005
Hot Cement and
Hot Weather Concrete Tests, IS015, Portland Cement Association,
12 pages, 1954
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