New construction, floor slab, cracks are fine

Hi,

at our place, the base slab was poured during blazing heat this month and then covered with a black foil.

However, it was not moistened or anything.
When we went to the construction site in the afternoon the next day to check, the foil had been blown away in some places.

I discovered cracks.

Today I went there again and took a quick look at the base slab and lifted the foil in some places and noticed the following, see pictures.
The one picture from the edge is at the bay window.

It is a WU concrete.

Is all this serious? Does it have to/can it be repaired?

All good, all normal.
Don't worry, the slab is stable.

As someone once said so nicely: Concrete workers and bricklayers are not precision workers

Best regards, Yvonne

I don't know, I wouldn't dismiss that so easily. There are clear regulations for post-treatment, and if they are not followed, lower strength is to be expected. Why should one accept concrete that does not achieve the agreed or required strength? Why should one accept a trade that has not been carried out according to the recognized rules of technology? I would write a defect report.

Hi, so the site manager responded to my email with the pictures as follows:

The cracks you marked in the photos are shrinkage and drying cracks and have no impact on the foundation slab. These cracks will not be treated afterwards either.

The defects in the edge area will be mortared when laying the first row of bricks.

You can believe it now or not.

That is quite an unusual formwork at the corner. What material is it made of? Is that an external corner where a rising wall will later rest? With these defects, is the prescribed concrete cover even maintained?

In general, too rapid drying of the concrete can have negative effects on strength and tightness, and especially tightness is relevant for waterproof concrete (WU concrete). At temperatures above 25 °C, rather strict requirements for curing must be observed, for example, watering. For WU concrete, curing is also explicitly mentioned in the WU concrete guideline, if I am not mistaken. If it were my contractor, I would have him provide proof of strength, tightness, and concrete cover, whatever it takes. Because before you notice the long-term effects of a poorly executed floor slab, the warranty has already expired.

Hm, thank you for your answers, I could also talk to the site manager about the concrete cover etc., but he might tell me stories and I wouldn't understand it anyway.