A bachelor level concept on hot and cold weather concreting

1. Concrete Presentation
Submitted To: Engineer Zain Ul Abideen

2. GROUP 8
Name Class #
Muhammad Asees Khan 168
Abdul Basit 169
Muhammad Arif 170
Haris Amjad 171
Hamza Saeed 172

3. Hot Weather Concrete
Muhammad Asees Khan(168) ,
Muhammad Arif(170)

4. HOT WEATHER CONCRETING
• Hot weather is any combination of conditions which
tends to damage the quality of freshly mixed concrete or
hardened concrete by accelerating the rate of moisture
loss and cement hydration, or otherwise causing cracks.

5. EXPLANATION:
The problems of hot weather are usually encountered
in the summer season but the associated climatic factors of
high wind speeds and solar radiation occurs all the time.
Rapid rate of evaporation of moisture from the
surface of newly placed concrete and accelerates the setting
time, produces cracks in the concrete among a variety of
other considerable problems.

6. Why we consider this?
The parameters in hot weather should be taken into
consideration because of its substantial potential effects on fresh
and newly placed concrete.
Increase in water demand which in turn increases the water to
cementitious ratio.
Slump loss.
Loss of Entrained air in concrete.

7. CONT:
Quicker setting time.
Placement of concrete.
Increase tendency for thermal cracking

8. Relationship Bw Loss Of Slump And Temperature:

9. Relationship Bw Water Content And Temperature:

10. Relationship Bw Compressive Strength And Age Of
Concrete:

11. SOLUTIONS
 Use of water reducing and set retarding admixtures. Extended
set-control admixtures may be used for long haul deliveries or in
extremely high temperature.
 Using low heat cement or use of fly ash and slag cement can
reduce potential problems with high concrete temperature.

12. CONT;
If possible, avoid the hottest part of the day to place and finish
concrete.
 Do not sprinkle water on the surface of slabs to facilitate finishing.
 In case of extreme high temperature conditions or with thicker
(mass) concrete sections, the concrete temperature can be lowered
by using chilled water or ice as part of mixing water.

13. CONT:
 The ready mixed concrete producer uses other measures such as
shading and sprinkling the aggregates to lower the temperature.
 If low humidity and high winds are predicted, windbreaks, mist
fogging or evaporation retardants may be needed to minimize the
potential plastic shrinkage cracking in slabs.

14. Fogging On Concrete;

15. Ice Cubes;

16. Plastic Shrinkage;

17. Thermal Cracks

19. CONCRTETETECHNOLOGY

20.  Concrete
Cement Coarse aggregate Water
Fine aggregate Admixture

21.  ACI Definition of COLD WEATHER
A period when for more than 3-days, the following conditions occurred:
 The average daily air temperature is less than 40 F.
 The air temperature is not greater than 50 F for more than one half of any 24
hours period.

22. TEMPERTURE
(Fahrenheit)
SETTING TIME
(hrs)
60 8
50 11
40 14
32 Freezing phenomenon

23.  Major Problems can be:
Delay Setting time
Freezing of concrete at early stage
Placing of concrete on Ground

24. Use of Material
Precaution in field

25. Use Of Material
Type-III cement
Air entraining agent
Admixtures

26. Delayed removal of form work:
Since rate of strength is slower,so
form works needs to be placed for
longer time.
AND
Covering the concrete to avoid
heat loss.