Concrete or Sand+Cement?🤔

[westcoast]

Annoyingly after final floors went down (microcement) we noticed shower drain rocking and subsequent cracking of microcement.

 

turns out linear drain wasn’t seated correctly into mortar by plumber - 5mm gap under ‘wing’ of drain.

 

Gap fixed now with epoxy.

 

 

You can see I removed a lot of screed cement during my investigation:

 

 

should I repair this with concrete or sand+cement? 

in any case I’m thinking of using some steel dowels to connect all the elements.

 

its about 100mm deep

but only 15mm deep over pipe!

Edited January 23, 2024 by westcoast

[Mr Punter]

Christ what a mess!

 

I can't see how that could be patched in, but I have zero experience with laying microcement.

[Conor]

Is this the finished shower surface? How are you going to waterproof the patch? You'll have to use something that won't shrink. 

[westcoast]

Microcement people are coming back to sand down whole tray and re apply microcement so waterproofing is not an issue

 

im just wondering if I should pour concrete in the hole for strength or match the screed material (sand and cement)

Edited January 23, 2024 by westcoast

[Conor]

I'd use concrete with small stones, just because it's cheaper and faster. I'm sure you've some insualtion to slot in first then foam in to place.