Tanking Slurry Failed?

[cdbe]

Well the OP did it, only they know how well and whether it's worth another go. Zooming in on the photo it looks like it's been put on areas of loose and flaky mortar or efforvescence, which it won't stick to:

I generally use an old but sharp woodworking chisel to prep walls - if that doesn't get it off I'm happy for it to stay.

I would suggest that if the pressure was that great there would be significant water penetration, not just a bit of dampness.

 

[Ivor Windybottom]

It wasn't ever going to work.

The first photo in the thread shows that the slurry is itself wet, therefore it can't possibly waterproof anything.

Even if it was waterproof, then it would only work if applied to the outside. Then the water would be pushing it onto the wall rather than pushing it off.

Tanking is used inside a bathroom wall to stop water FROM the room entering the wall. It can only ever stop water entering, it can't hold back the tide from within the wall once it's in there.

Leave it on, it won't do any harm. You'll need to do something outside to dry the wall out, probably involving proper work using a shovel or a digger rather than any quick fix with some miracle wonder-goo.