Different types of plaster on each other?

[Sir Duke]

The construction workers at home had some mortar left over after building cinder block walls for our new crawl space. Since there were a few bags left over, they happily started plastering with the same mortar. https://www.byggmax.se/gjutning-och-husgrund/cement-och-bruk/mur-och-putsbruk-b-p0112

Our supervisor is not available right now, but I remember he said before that it was important to plaster with "KC-bruk." (Does that mean lime-cement mixture??)

Anyway, I got hold of the foreman, and he asked the construction workers to go and buy plastering mortar instead. https://www.byggmax.se/gjutning-och-husgrund/cement-och-bruk/puts-och-murbruk-c-p0113

However, the mortar sat on the cinder block wall for a couple of hours. They have started scraping it off. How important is it to remove everything? (Probably won’t be possible without damaging the cinder blocks behind...) And does the plaster mortar adhere on top of the mortar? What will the long-term result be?

Thanks in advance for the help!!

 

[SBH]

there's always a bit of mess so it doesn't harm anything essential.
good that they scraped it off

 

[Sir Duke]

But does a "better" use attach to a "worse"? Because they can't remove everything.

 

[SBH]

worse? b-bruk a little harder than kc-bruk I would say. so kc-bruk = a little worse, softer

 

[Sir Duke]

What???
Yet they call C-bruket plaster mortar, and B-bruket masonry mortar...
Is it better to use masonry mortar as plaster then?

 

[SBH]

a.
b- The bruket becomes harder. Does not follow the wall in motion.
c- The bruket is softer and follows the wall's motion more. Worse in a good way.

 

[Sir Duke]

OK and do they attach to each other?

 

[SBH]

have a couple of times knocked off plaster mortar. usually more where c-bruk has been applied on b-bruk.

 

[Sir Duke]

OK then I can sleep peacefully I guess
Thanks for the info!

 

[MaxPax]

KC mortar is available in both class B and C, "Render mortar" is also available in both class B and C. "KC" simply means that the binder used is lime and cement, so "KC mortar" does not indicate a specific hardness class.

 

[Steinmeister]

I have used mortar b from Byggmax in my basement after a recommendation from a mason. I have concrete block as a foundation. I plastered the outside with loosely mixed b mortar with a little extra cement. We'll see if it stays on after 20 years.

 

[Sir Duke]

Aha.

For an amateur like myself, it feels more logical to use putsbruk than murbruk.

 

[MaxPax]

Aha.

For an amateur like myself, it at least feels more logical with plaster mortar than with bricklaying mortar.

Fully understandable.

Check the descriptions on byggmax, where it states that the plaster mortar can also be used for bricklaying under certain circumstances, and the bricklaying mortar can be used for plastering under certain circumstances. The name mostly shows what it is generally used for in the first place.

However, when it comes to special mortars for more specific applications, it can become more critical.

 

[Steinmeister]

To provide you with an answer to a question. The rule is that the hardest mortar should be underneath. So in your case, you have the mortar in the correct order, b mortar underneath and then a c mortar on top of it.

 

[Sir Duke]

Perfect, thanks for the info!