High temperatures can lead to issues with concrete like loss of workability, increased risk of cracking, and thermal cracking. To address this, the temperature of concrete ingredients should be lowered by cooling the water, shading aggregates, and using set-retarding admixtures. In large pours, lower cement content mixtures and measures to control temperature differentials within the concrete mass are important. For cold weather, air-entrained concrete and protecting plastic concrete from freezing are crucial.

3. High temperature leads to:
Loss of workability and higher plastic shrinkage
Risk of cold joints
More evaporation of curing water resulting shrinkage cracking
For large masses of concrete, results in thermal cracking due
to difference of temperature between interior and exterior
concretes
Total pore volume as well as the size of pores increase

4. 1. Plastic cracks are usually parallel to each
other, between 1 and 3 feet apart, and do not
cross the perimeter.
2. Shrinkage cracks in concrete usually appear
to be discontinuous. The crack will travel
along in the concrete, taper to a stop, and
then continue beginning in a parallel line to
the first crack, traveling again through the
concrete.
3. Thermal cracks appear as random pattern
cracking at the surface of the member. They
usually occur perpendicular to the longest
axis of concrete.
1
2
3

5. The temperature of the concrete can be lowered by lowering the
temperatures of its ingredients.
It is much easier to cool water than cement and aggregates.
It is even more effective to place some ice in water.
Aggregates stockpiles should be shaded and sprinkled with
controlled amount of water.
Cement content should be as low as possible.
As an early set is expected, a set-retarding admixture should be
used.
 Concrete surface should be protected from direct exposure to
sun.

6. In large concrete masses, there is the danger of thermal
cracking. This cracking occurs due to temperature
gradient within the concrete mass. Following measures
should be taken in large concrete masses.
Design mixtures using lower cement contents or low heat
cement and higher amount of SCMs (supplementary
Cementitious Materials like Fly ash etc.)
Use water reducing admixtures
Place concrete at low ambient temperature
Cool the ingredients of the concrete
Use insulation to help control temperature differential

7. Cold weather concreting refers to an ambient temperature
of 5°C (40°F).
Fresh concrete starts freezing
mixing water converts to ice
Ice has more volume than water and exerts stress on concrete
No water is left for hydration
Temperature difference between surface and interior leads to
cracking

8. Use air-entrained concrete
Keep surfaces in contact with concrete free of ice and snow
and at temperature above freezing prior to placement
Place and maintain concrete at the recommended
temperature
Place concrete at the lowest practical slump
Protect plastic concrete from freezing or drying
Protect concrete from early-age freezing and thawing
cycles until it has attained adequate strength
Limit rapid temperature changes when protective measures
are removed.

9. Non air-entrained concrete,Non air-entrained concrete,
cracked due to freezing andcracked due to freezing and
thawingthawing
Air-entrained concreteAir-entrained concrete

10. Non air-entrained concrete,Non air-entrained concrete,
cracked due to freezing andcracked due to freezing and
thawingthawing
Air-entrained concreteAir-entrained concrete