Cracks in freshly poured floor slab

Hello! For my house construction, a floor slab was poured early this morning (house = semi-detached house, approx. 135 sqm).

The concrete was spread on the mesh framework by the workers. Afterwards, air was applied with a vacuum cleaner-like device. Then a worker used a rake to create a grooved pattern in the concrete so that small waves or ribbing were formed.

Unfortunately, cracks appeared this evening. Some are over 75 cm long, and some are over 3 mm wide. Now I don't know if they are problematic or not. Concrete is still something new to me. Interestingly, these appear where the concrete is smooth. About 40% of the floor slab has no ribbing. Next door, another house was built identically (at the same time). Here, the entire floor slab was ribbed, and there is not a single crack.

I involved the site manager, he remained quite calm and said this can occasionally happen. But he will personally inspect it tomorrow morning.

Are these so-called surface shrinkage cracks?
Are they problematic?
Are there methods to repair them?

I called the site manager directly and asked if I should do anything (e.g. water). He said that is not necessary. This morning it was a bit rainy, but from midday sunny and about 24°C.

I am very much looking forward to answers!!! Many thanks in advance for your replies!

Alex

Hello Acze

the cracks are superficial. Completely normal.
And the "vacuum cleaner" was a vibrating bottle to vibrate the air out of the concrete.
The employee smoothed the surface with the "rake" or spread it horizontally.
Everything is within the green range.

Steven

The cracks sometimes appear too wide to be shrinkage cracks. In my opinion, the permissible crack width depends on many factors. You could ask your contractor for a written assessment based on the [standards]. Was the fresh concrete not covered during the rain?

Hello,
how warm was it on the day of concreting? The cracks occur due to lack of curing of fresh concrete. They may not lead to damage but they are NOT NORMAL.
If the cracks are wider than 0.4mm, I would have them repaired.

Best regards.