Crumbling concrete floor in new extension?

[MyBuggyIsOutToGetMe]

If you had a concrete floor poured in a new extension - by which I mean you would expect to lay LVT or engineered wood or whatever over the top - did it crumble at all? Ours was only poured a month or so ago and is crumbling like crazy. Have asked the builder (not in person as haven’t seen him) but he’s not got back to me yet. Apparently it might need a screed on top (according to our kitchen fitter). But I’m worried the actual concrete is defective in some way.

Has anyone had anything like this?

It should not be crumbling

Was it poured in hot dry weather?

Was it mixed on site or from a readimix truck?

It’s 99.99% the screed. They have mixed it too dry (which makes it easier to lay). The concrete slab underneath will be fine.
You can seal it with a kind of liquid cement spread over the top.
Take professional advice.

We have this too - does anyone know what 'professional' advice we should take, I have no idea where to start to get it sorted (ie is it a builder, floorer something else I should be looking for)?

The guy who will lay the floor.

Search and look on YouTube etc. Lots of information on it.

@PigletJohn , thank you - I wasn’t on site but I think it was from a truck. Our builder is being elusive but I am going to try to corner him this week. It just doesn’t look right. It was poured in early September so it was warm and dry but I wouldn’t say hot (we are E England).

Could it actually have been an anhydrite screed? Notorious the world over (and hence the reason they have fallen out of favour) for drying with a sort of crust on top that you either need to break up and level or accept that your flooring will forever move, lift and crack. Although I suspect that you’d know if that were the case as you’d have been told it takes roughly 35000 years to dry. If it’s not an anhydrite screed it certainly sounds like there’s been a stuff up with the mix. Our concrete sub base was laid about a week before that blistering heat wave that we had in July/August and although it did crack slightly it was absolutely nothing in the grand scheme of things. Certainly not crumbly!

@NoParticularPattern , I don’t know - I will ask. We were told to allow a day per mm for it to dry out, which would be about 70 days and take us to mid November. But the crumbling is something else. I’ll have a Google. Just wondered if this was a common thing and if it is going to cause issues going forward.

@PigletJohn I'm curious, please tell us if concrete mixed from a truck is the good stuff or not? Many thanks

Very likely to be good.