Pour self-leveling concrete on old slab, primer or not?

[marmander]

Hi,

I don't know if I posted this in the right forum, please move it if needed...

I am going to level an old slab in a machine hall/garage/workshop. About 60 sqm will be filled with about 6-12cm (uneven as mentioned)

I'm planning to use self-leveling concrete (order a truck with a chute).
K30 with a flow additive?

Now for the questions; Should I use primer and if so, which one?

I've heard that this self-leveling concrete can be made completely smooth by just vibrating it and manually spreading it with some kind of screed, is that correct, or is there anything else I need to consider?

Best regards/
Simon

 

[Alan]

It should be spread out and vibrated. Just make sure that the new bars you're placing over the surface are at the correct level so you can pull over them with the "slodan." Are you doing it yourself or do you have help? It may take a little time, but prepare everything so that when the vehicle arrives, you can essentially pour and vibrate immediately.

//
Alan

 

[marmander]

It should be able to vibrate out. Just make sure that the new bars you place over the surface are at the right level so that you can drag over them with the "slodan". Are you doing it yourself or do you have help? It can take some time but prepare everything so that when the truck arrives, you can basically pour out and vibrate immediately.

//
Alan

I might be able to arrange someone or a few people to help, but no one with direct experience in it.

The bars? You mean I still need something to drag the slodan against?

Exactly the right level is hard to determine since I have to estimate the amount and then let it be at the level it becomes.

From what I've heard, you don't need something to drag afterwards, as the concrete flows so easily that it almost settles "level" on its own, as long as you spread it fairly...

What about the primer? No one has a direct and good answer regarding that?

//SM

 

[hempa111]

If the surface is clean and reasonably rough, it should be fine without primer. By reasonably rough, I mean broom finished or rougher. Then you probably shouldn't expect the concrete to self-level completely because there is a difference between concrete and self-leveling compound. But order full-flow and it should go well.

 

[marmander]

If the surface is clean and reasonably rough, it should work well without primer; by reasonably rough, I mean wood-textured or rougher. You probably shouldn’t expect the concrete to level itself completely because there’s a difference between concrete and self-leveling compound. But order full-flow and it should be fine.

It was an old "bonnagjuten" slab, cleaned it with caustic soda and water. Sprayed water just before the truck came.

The concrete didn’t spread as well as I thought, worked hard with my homemade screed, got the 6 cubic meters out reasonably well (doing it all by myself, should have been two people with screeds and one measuring with a laser). There were a couple of spots that were lower than expected, but it doesn’t bother me too much. The surface was quite okay, but I chose to sand it with ABS sandpaper (stones).

All in all, the slab cost about 14k SEK including reinforcement, rental of ABS sander, and 6 cubic meters of k30 C4 concrete.

In a couple of weeks, I will be laying tiles, 10mm thick through-colored granite ceramics.

Best regards,
Simon