Hi

Without going into great detail, is there an adhesive that will stick
a narrow capping slab, say 25 cms wide, on top of a cement screed.
I really don't want the depth of another mortar course and would like
to avoid hacking off the old stuff. The wall is outside and so the
adhesive would have to cope with damp conditions.

Are there any recommendations, even commendations please ?

TIA Andy