Patching a solid floor before self level

[SUFCDAN]

I am going to be self level the floor prior to wood flooring.

There was a patch that had been done before, it had a few cracks and sounded hollow, so I’ve taken it up, it’s chunks of around 25mm that came up.
Probably be just under a metre square when all dug up.

I noticed that the cement that came up had not adhered to the concrete sub floor (the hollow sound)

I was going to damp it, then an sbr slurry, while tacky fill it in, should I used a 3 to cement mix (sharp sand) and a bit or sbr

Or should I do a concrete mix, if so can you tell me what to use and mix? Thanks all.

 

[ted456]

It looks like the sand and cement screed is on a dusty soil but you say that its on a concrete sub-floor?
If its concrete then it needs brushing/vacuuming clean of all sandy bits and the suction taken up with water and a slurry. then 3:1 sand and cement or a 3:1 mix with stone dashings in it.

 

[SUFCDAN]

It looks like the sand and cement screed is on a dusty soil but you say that its on a concrete sub-floor?
If its concrete then it needs brushing/vacuuming clean of all sandy bits and the suction taken up with water and a slurry. then 3:1 sand and cement or a 3:1 mix with stone dashings in it.

Yes it’s concrete, it’s a poor bond, is that sharp sand I use 3/1.

With the slurry some say let it dry overnight some say tacky ? It’s a little confusing.

Thank you very much for the reply