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In hot weather condition suitable means shall be provided to ensure that the temperature of
the concrete when deposited in the forms does not exceed 30ºC. Chilled water
shall be used to reduce the temperature of the mix. Aggregate stockpiles shall be
shielded from direct sun. Mixing water shall be protected from direct sunlight by
sheltering the storage tanks with shades painted white on the outside. All
formwork and reinforcement shall be sprayed with water when necessary to keep
temperatures below 30ºC before concrete is placed.
Any concrete with a temperature in excess of 35ºC at time of placement shall not be
used. Concrete placing shall be completed as quickly and efficiently as possible,
and exposed surfaces immediately covered to minimize the evaporation of water.
To prevent early drying and cracking, the relative humidity shall be kept high and the concrete surfaces kept moist by spraying with clean water and covered with wet hessian.
One of the desirable properties of concrete especially which are supplied BY RMC for general work, is to have delayed Initial Setting Time of concrete and early (than usual) final setting time of concrete..
High temperature of concrete will have early Initial Setting time and will cause thermal cracking and cold joint in concrete.
Preferably concrete with high temperature shall not be used but final call shall be taken by considering the type of structure or may be used for some non structural work
Temperature 38 degree centigrade shown that Hydration Reaction was started, and its life time may over 1 hour (Without Admixture). As practical, fresh concrete which have life time more than 2-4 hours (With Admixture) will be rejected.
In case of mass concrete structure, Thermo-Crack or Micro-Crack will occurred if fresh concrete which have temperature higher than 32 degree centigrade too.
Hence, we shall monitoring for both factors on quality control process. And concrete will consider to reject, either temperature is higher than 32 degree centigrade or life time is over recommendations.
Expansion will take place if the ratio of mixture of cement and sand is high, for example if you take one bag of 50kg cement and mix with 10 head pan of sand, the mixture will not resist the temperature but if the quantity of sand is slightly equal to the quantity of cement and the span of the iron rod is between 4 inches to 6 inches then it will be difficult for expansion or crack to take place.
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