Because, whilst the wall is 100 years old, it has been made good so many times with all sorts of cement, my only interest at the moment is preventing water getting into the attached garages. To repair the wall properly would require considerable expenditure which my client is unlikely to agree.
In any case, lime mortar permits the structure to breathe, and a retaining wall whose lower 1.5m section is up against rocks and soil, doesn't need to breathe.
Anyway, it's not my wall, and the job's done now, with a neat little fillet of mortar capping off the silicone in the crack. (In the end I used Evo Stik trade construction sealant, which is neutral cure, and has a 25 year life expectation)
In any case, lime mortar permits the structure to breathe, and a retaining wall whose lower 1.5m section is up against rocks and soil, doesn't need to breathe.
Anyway, it's not my wall, and the job's done now, with a neat little fillet of mortar capping off the silicone in the crack. (In the end I used Evo Stik trade construction sealant, which is neutral cure, and has a 25 year life expectation)