Winter Concreting

For concreting in winter temperatures, as a rule, a certain Minimum temperature of the concrete is prescribed. At air temperatures between + 5 °C and - 3 °C, the concrete temperature at placement must be at least + 5 °C If cements with low heat of hydration (LH cements) are used, even mostly + 10 °C prescribedn. If the temperature is lower than -3 °C, a concrete temperature of +10 °C when placing always prescribed.

Basically: The lower the concrete temperature, the longer the strength development takes. Example: Concrete at + 5 °C needs approximately twice the time for strength development than concrete at + 20 °C . If the concrete reaches the -10 °C limit, the hardening process comes to a complete standstill.

• Solidification and moisture development is delayed. This results in longer stripping times and a longer curing period. The young concrete must therefore be protected for longer.
• Structural damage due to freezing through too early: If young concrete freezes before freeze-through resistance is reached, the concrete structure may be disturbed and permanently damaged due to the increase in volume of the freezing water contained in the concrete.
• Reduction of the adhesive bond between concrete and reinforcement or top and bottom concrete due to ice and snow accumulation on formwork or reinforcement.
• Risk of frost damage when concreting against frozen ground, formwork or structural elements, if due to their low temperature the concrete freezes through before reaching its freeze resistance.
• Risk of crackingThis is the case when high residual stresses occur due to higher temperature differences in the component between the edge and core zone after stripping or removing heat-insulating covers. In addition, cold, dry air - also in combination with wind - can lead to increased drying of the concrete in winter and thus to increased cracking.