ᐅ Basement slab poured, now awaiting cold days with frost

Our foundation slab was poured on Monday at an outside temperature of 0°C (32°F). Today it is 10°C (50°F). The general contractor said temperatures down to -6°C (21°F) would still be acceptable, but they decided to postpone the whole process by a week, which is why it was done on Monday.

We experienced a similar situation with the temperatures during the last concrete slab on the upper floor. I was also very skeptical, but as some have already mentioned here, the temperatures were still within an acceptable range. The curing of concrete, known as hydration, is an exothermic process, meaning it releases heat energy. So the slab essentially "heats" itself. After our attic had dried, we were able to remove the frost-covered protective foil on top, which was the only critical part of the whole process. 🙂

By the way, on other construction sites around here, concrete pouring was also carried out at temperatures down to -5°C (23°F), not just on ours.

Allthewayup schrieb:

(...)
By the way, all construction sites here were also concreted down to -5°C (23°F), not just ours.

Arguably one of the most foolish arguments ever. Especially since you don’t actually know in each case which additives construction company xyz ordered from the ready-mix plant compared to company abc, or how thoroughly the foundation slab is cured afterwards.

With most builders, you can expect the following procedure:
Pour the concrete, cover it with a plastic sheet, done. Nobody comes back the next day to check whether the sheet or even the thermal insulation underneath is still properly in place. The only person who inspects this daily is the homeowner... who usually ends up bearing the consequences around Christmas time.
Because even if something goes wrong, the builders are on Christmas break and no one can be reached by phone...

xMisterDx schrieb:

This is one of the most foolish arguments ever, especially since you clearly don’t know which additives company xyz ordered from the concrete plant compared to company abc, or how thoroughly the foundation slab is cured afterward.

With most construction companies, you can expect the following procedure:
Pour the concrete, cover it with a plastic sheet, done. Nobody comes back after a day to check whether the plastic sheet—or even the thermal insulation underneath—is still properly in place. The only person who checks that daily is the builder... and that person usually ends up paying the price during the Christmas period.
Because even if something goes wrong, the construction companies are on holiday, and you can’t reach anyone by phone...

That was not an argument. The arguments are in the paragraph above, hence the paragraph.
C25/30 concrete does not require any special additive mix or frost protection measures at the mentioned temperature range, except for a sealed plastic covering. Of course, you can always play it extra safe everywhere and spend money here and there if that helps you sleep more peacefully.