2. Introduction
Difficulties in Hot Weather
Precautions
Effect of High Concrete Temperature
Properties of Concrete Materials
Durability issue of concrete
Conclusion
3. Hot weather conditions include:
- High ambient temperature (T>35⁰C)
- High concrete temperature
- Low relative humidity
- Solar radiation
4. Difficulties in Hot Weather
Increased water demand
Accelerated slump loss
Loss of compressive strength
Increased tendency of plastic shrinkage
cracking
5. Precautions Depends on
Type of construction
Characteristics of the materials being used
The experience of placing and finishing crew in
dealing with the atmospheric conditions in the
site
7. Use materials and mix proportions that have a
good record in hot weather conditions
Cool concrete and its ingredients
Use a concrete consistency that allows rapid
placement and consolidation
Reduce the time of transporting, placing,
and finishing as possible
8.
9. Contd…
Increase the rate of setting and shorten
the length of time
Setting time can be reduced by 2 or more
hours with a 10°C increase in concrete
temperature
10.
11. Contd…
Increased tendency for cracks to form
both before and after hardening
Rapid evaporation of water from freshly
placed concrete can cause plastic-
shrinkage cracks
Cracks may also develop in the hardened
concrete
12.
13. Lower the temperature of concrete
materials before mixing
The contribution of each material is
related to-
Temperature
Specific heat
Quantity of each material
14. Where T = temperature of the freshly mixed
concrete, °C
Ta, Tc, Tw, and Twa = temperature (°C); Ma, Mc,
Mw, and Mwa = mass(kg), of aggregates, cementing
materials, added mixing water and free water on
aggregates respectively
Contd…
17. Associated with hot-weather concreting
Can occur any time ambient conditions
produce rapid evaporation of moisture from
the concrete surface
Cracks occur when water evaporates from the
surface faster than it can rise to the surface
during the bleeding process
20. Precautions to Minimize
Plastic Shrinkage Cracking
1. Moisten concrete aggregates that are dry
and absorptive
2. Keep the concrete temperature low by
cooling aggregates and mixing water
3. Dampen the subgrade and fog forms prior to
placing concrete
4. Erect temporary windbreaks to reduce
wind velocity over the concrete surface
23. It can be used effectively in construction of large
concrete elements in hot weather condition
More research needs to be carried out on thicker
concrete specimens
