Either demolish the wall.
Repairing a concrete retaining wall.
It will adhere to the rough concrete in the crack which after it cures will be just as strong as the rest of the wall.
The easiest way to mix mortar is to follow the instructions on the packaging.
Many garden and boundary walls are created using inexpensive cement blocks.
Mortar is essentially concrete that you will mix and then use to fill the cracks in the concrete retaining wall.
Retaining wall repair options whether a retaining wall is built of stone block concrete or wood it can begin to lean.
The injection process fills the crack from top to bottom from inside to outside.
The only way to repair foundation wall cracks successfully is by the injection process.
Unfortunately while economical these blocks are susceptible to being damaged by the elements and many of the walls built with them begin to crumble and appear dilapidated.
To fix the mortar carefully chisel out mortar to a point of a little over 1 2 the depth of the brick.
Injecting a typical wall crack with an epoxy or urethane resin is done under pressure pushing the material from the inside all the way to the outside.
This mortar is typically one of the first things to show wear on a well made wall.
Once that has been done you may want to start mixing your mortar check on amazon.
Use a wire brush check on amazon to brush both ends of the walls and then try a vacuum pump to suck out all debris in.