CONCRETE SLAB EFFLORESCENCE

What is your question?

The thing is that I've always seen efflorescence as a long process and in these sites, it comes fast. Could it be that it is something else? And is it the result of an important humidity problem?

My first house had a cmu basement wall that was not filled or reinforced. I also suspect that it had little or insufficient waterproofing or drainage measures on the outside since it too had efflorescence.

I would go down there with a flat blade and scrape off the efflorescence about every 2 to 3 weeks. So I know that at least in below grade cmu (especially during the rainy season), it can reoccur on a pretty regular basis. It is usually harmless and seen more as an eyesore than anything else. It looks like the top surface of the slab is eroded, but my guess is that when the tiles popped up or were removed, it probably took the skin surface of the concrete with it.

Its not a humidity problem, humidity is generally associated with water in the air. Your problem is due to moisture in the soil.