It is believed that the normal temperature of hardening of concrete is + 15- ÷ -20 ° С. When the temperature is lowered below +15 C, the rate of hydration of the cement decreases. At a concrete temperature below 0 ° C, curing is almost stopped. At a temperature of -3 + -6 ° C, the bulk of the water in the concrete freezes. When thawing the concrete, the hydration processes are resumed and the concrete continues to gain strength. It should be borne in mind that when water freezes the water expands and loosens the cement stone, therefore, even when (after thawing) conditions for hardening are created, the strength and frost resistance of concrete are reduced.
Therefore, in order to provide the necessary set of concrete strength in winter, it is necessary to create conditions under which cement hardening will take place, first of all, the presence of a liquid phase. This task is solved by holding the concreted structure at a positive temperature. In this case, thermoactive formwork is used, the use of preheated concrete mixes (provided by heating of the mixing water and fillers), followed by covering the surface of the structure with heat-insulating materials, using antifreeze additives.
The most effective for winter concreting is the use of a complex system that includes the following components:
PJSC Pigment represents a wide range of additives for winter concreting. We offer concrete manufacturers as systems for winter concreting: Kratasol-Krio + plasticizers (including low-sulfate); And complex additives, including antifreeze and plasticizing components. In this case, complex products as a plasticizing component include polymethylene naphthalenesulfonates, aliphatic ionomeric superplasticizers, polycarboxylates. The choice of antifreeze additives must be carried out based on the conditions of production and use of concrete (materials, the number of weight additives for additives, methods of concrete care on the construction site). So in the case of the possibility of simultaneous dosing of two additives, it is economically expedient to use the antifreeze (Kratasol-Cryo) and the plasticizing component (eg. Kratasol-Extra), which will allow to react flexibly to the change in the ambient temperature. When combining electrical heating and antifreeze additives, it is advisable to use Kratasol-Krio PC (the minimum content of electrolytes in concrete).