The most difficult time of the year for concreting is winter, because at low temperatures the hardening process of concrete slows down and there is a danger of freezing of the concrete mix. Freezing in turn leads to a dangerous decrease in structural strength.
Preparation for winter concreting includes planning and comparing alternative options for all participants in the concreting process: in addition to facility managers and construction crews, suppliers of materials and equipment should also take part in the planning. Coordination and careful preparation require the following questions:
The fastest concrete pouring into the formwork, without unreasonable delays;
The fastest possible creation of thermal protection of the structure: during concreting or at the end of pouring;
Thermal insulation of the formwork of pillars and walls, and the use of hot concrete;
To guarantee a set of strength of the lower parts of vertical structures, the use of additional heating;
Creating thermal protection for the upper parts of vertical structures;
To guarantee a set of strength, heating supports, edges and areas of occurrence of cold bridges of horizontal structures by heating;
and Avoid the use of hardening concrete additives;
Avoid concreting at low temperatures, due to the slow hardening of concrete in case it is impossible to use additional heating to accelerate hardening;
Avoid the use of hot concrete when pouring massive structures, since the temperature is more than 50 ° C in a hardened structure reduces its final strength.
Possible alternative solutions:
increase in concrete strength class;
use of quick hardening concrete;
use of hot concrete;
the use of well-insulated formwork of pillars and walls;
the use of formwork with thermal insulation in horizontal structures;
infrared heating (heating by heat rays);
electrode heating.