PRECAUTIONS FOR MIXING, PLACING, CURING, AND TESTING OF CONCRETE IN HOT WEATHER
In mixing concrete in temperatures of about 47 C? or more, cold water (7 C?) is to be used and to be kept cold by insulating pipes and tanks. Tanks or trucks used for storing or transporting water have to be insulated and / or painted white. Reduction in water temperature may be accomplished by refrigeration or by using ice as part of the mixing water (40% of the mixing water by weight). Aggregates have to be also shaded. Careful sprinkling of fog spraying of coarse aggregate stockpiles is to be used to reduce aggregate temperature by evaporation and direct cooling.
In normal conditions (16 – 27 C? ) cooling water and using ice are to be stopped while in temperatures between (32 40 C? ). Water shall be cooled to about 12 C? or ice shall be used as much as about 25% of the mixing water by weight.
Concrete has to be placed in layers shallow enough to assure vibration well into the layers below. Also, concrete of large area shall to be placed in strips, 25 cm apart, after casting all strips. Placing the 25 cm areas shall be made, in order to prevent shrinkage cracks. A fog nozzle shall be used carefully to cool air, and to cool the forms and steel immediately a head of placing concrete.
Water curing shall be continuous and all exposed surfaces (horizontal , vertical and otherwise) shall be covered with saturated materials (burlap, cotton mats, carpets, etc.), Curing water shall not be much colder than concrete.
Test specimens shall be maintained at proper temperature ( 16 – 27C? ) and protected from loss of moisture for 24 hours of initial curing. Specimens shall be stored in moist condition at 23 C? until testing, and during transfer they shall be protected and handled carefully. Beside other precautions specified in well -known codes and standards.