Cement/mortar for an older wall.

[Paul F]

We have a small wall against the street that is "falling apart." This is likely due to three factors: how it was made, age, and that a fence was screwed on top. It shouldn't be impossible to fix. But I've failed three times. I don't want to remove the wall.
Attempt one: used the completely wrong mortar. It looked fine for a month, then got worse than before the repair.
Attempt two: tried a fiber-reinforced combitex in limited areas. It became hard and good, but I had difficulty filling it out and failed to fasten threaded rods for the fence.
Attempt three: a year or two after attempt two, I used the same fiber-reinforced mortar. Seems to have become softer. I can easily scrape it, so I don't think it will hold. It has probably become too old even though the bag was unopened.

My main question is, which mortar/cement should I use? The suppliers refer to the retailers, where unfortunately I can't find the expertise!

 

[Claes Sörmland]

Isn't it a cast concrete wall? Then it’s a bit of a hassle to repair cracks because it moves in the crack, causing all repairs to fail. Can you break away segments of the wall where it has cracked, arrange new reinforcement bars, and cast onto the wall?

Repairing through plastering is done with cement plaster, like fine concrete (aggregate + cement). Not easy to make it look good; it just runs.

 

[cpalm]

Then it's a bit of a mess to repair cracks because it moves in the crack, so all repairs go to hell.

I've seen suggestions to chisel out a piece, drill holes on either side of the crack, and place some clamps made from bent rebar to fix the halves. (Before plastering/casting them in.) However, I've not tried this myself.

I've personally succeeded in filling cracks with thinly mixed repair concrete. The challenge is just getting it deep enough. You can chisel a bit and/or vibrate it down in a suitable way, I think.

 

[Claes Sörmland]

I have seen suggestions to chisel out a section, drill holes on either side of the crack, and attach some reinforcements bent from rebar to fix the halves. (Before plastering/casting them in). However, it's not something I have tried myself.

I have personally succeeded in filling cracks with thinly mixed repair concrete. The challenge is just to get it deep enough. You could chisel out a bit and/or vibrate it down in a suitable way, I think.

I believe in the first solution, about what I had in mind in my response.