Hello,
So once again the question: How critical is it to expose the foundation slab to the weather conditions? Shouldn't the frost skirt make this uncritical especially for the foundation slab??
I already know why I ask my interested parties if any of them have studied mechanical engineering
What should be considered when pouring the
foundation slab in
winter at low
temperatures?
Pouring concrete at low winter temperatures requires – similar to pouring concrete at summer temperatures – special measures and forward planning.
Delayed strength development:
The cold temperatures prevent or delay the setting and thus the hardening and strength development of the concrete. For this reason, concrete must be protected from frost damage in time.
Young concrete can suffer frost damage:
Due to the volume expansion of water present in the concrete when freezing, the already formed framework structure is weakened or destroyed.
A harmless one-time freeze-thaw of young concrete is possible if the concrete has reached a certain strength (compressive strength of about 5 N/mm2).
Crack formation:
During the setting process, internal stresses arise between the edge and core zones.
Depending on the strength development, these stresses cause cracks if the tensile strength of the structure is exceeded.
Efflorescence:
Due to delayed hydration, calcium hydroxide can be transported with the mixing water to the concrete surface and precipitate there as a white film.
Effective measures for concreting in winter are:
[*]Use of cements with fast strength gain and high heat development
[*]Increase of the cement content
[*]Avoid long waiting times on the construction site
[*]The construction manager should ensure that the fresh concrete has a certain minimum temperature according to the air temperature (e.g. up to -3°C the fresh concrete must have a minimum temperature of +10°C when placed and maintain this for at least 3 days; thus additional heat retention measures are necessary)
[*]The temperature of the fresh concrete can be simply and economically increased by warming the mixing water.
To be observed:
[*]The formwork and reinforcement must be free of snow and ice
[*]No concreting is allowed on frozen ground.
No concrete may be placed against frozen components
[*]Concrete damaged by frost must be removed before further concreting
[*]After placement, good thermal protection of the young concrete is necessary to minimize heat loss, e.g. by covering.
Frost-free foundation in winter
To prevent surface water from flowing under the structure and causing frost damage in winter, a structure must be frost-proof founded.
For this purpose, the foundation slab can be provided all around with a
frost skirt, which reaches at least 80 cm below the ground surface edge and is usually made of concrete.
Alternatively, frost safety can also be achieved by installing a gravel layer under the foundation slab, called
frost protection gravel. The bottom edge of this gravel layer must also reach at least 80 cm below the ground surface edge. The advantage of this variant is that the foundation slab can be wrapped all around and without interruptions, also from underneath, with thermal insulation.
Overall, it should be noted that pouring the foundation slab at winter temperatures is not recommended or should
exclusively be carried out by companies with experience in this area. Furthermore, you can certainly expect a surcharge because the work on the foundation slab at low temperatures is more time-consuming and also requires more effort.
Source: my homepage
Rhineland greetings
