Fosroc renderoc. Its not cheap but it's a decent self leveling mortar repair system you may be able to carry out the repair without formwork too.
It may be possible to repair it with a dry cement, sharp sand mix but you'll want to use a plasticiser. Also you will run the risk of cracking while it dries.
Fosroc renderoc. Its not cheap but it's a decent self leveling mortar repair system you may be able to carry out the repair without formwork too.
It may be possible to repair it with a dry cement, sharp sand mix but you'll want to use a plasticiser. Also you will run the risk of cracking while it dries.