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Frequently Asked Questions
Cement & Concrete
Technology Home > FAQs > Effects
of high concrete temperature
Q: What is the effect of high concrete temperature
(above 77°F) on transporting, placing, and finishing concrete,
and on hardened concrete properties?
A: When the temperature of freshly mixed concrete exceeds 77°F
(25°C) there may be a number of effects on the fresh and hardened
properties of concrete.
One of the effects on fresh concrete properties is accelerated setting,
which leads to a shorter time period for transporting the concrete
to the job site, and a shorter window for placement, consolidation,
and finishing of the material.
The higher temperature also leads to a higher water demand to maintain
the concrete at the specified slump, which can tempt the contractor
to add water to retemper the mixture leading to lower than expected
compressive strength of the hardened material. In addition mixtures
at high temperatures may require higher dosages of air-entraining
admixtures to produce the required air content for durability in
severe climates.
The effect on hardened concrete properties are a high early strength
but low ultimate strength compared to mixtures placed with a lower
temperature. In addition, if no precautions are taken, there is
an increased potential for plastic shrinkage cracking during the
finishing operations, and increased potential for cracking due to
volume changes caused by drying shrinkage and thermal effects.
The following references are valuable tools for
the prediction and prevention of these effects:
Portland Cement Association, Hot
Weather Concreting, IS014.05 , reprinted from Chapter 13
of Design and
Control of Concrete Mixtures, EB001.14, Portland Cement
Association, 2002, 12 pages.
ACI Committee 305, Specification
for Hot Weather Concreting, ACI 305.1-06, American Concrete
Institute, Farmington Hills, Michigan, 2007, 13 pages
ACI Committee 305, Hot
Weather Concreting, ACI 305-99, American Concrete Institute,
Farmington Hills, Michigan, 1999, 20 pages
Hot and Cold Weather
Concreting (CD057) Part of a series of training programs
on cement and concrete technology, this CD provides an introduction
to the effects of hot or cold temperature on the properties of concrete
and the general requirements for producing concrete in hot or cold
weather.
FAQ: What
precautions do I have to take during hot-weather concreting?
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