Repair larger through-hole in exterior wall of aerated concrete - choice of mortar?
Hello specialists! 
I am planning to remove a ventilation pipe with an associated fresh air vent that is located in the outer wall. The wall is made of aerated concrete with a layer of plaster on the outside. I keep googling but only find low-alkaline plaster mixes that can be applied in thicknesses of just a couple of centimeters. That doesn't work so well for a larger hole. Mine will be just over 20-25 cm. Do you have any tips on what might be suitable? Is house fix the way to go? Maybe too hard for it to turn out really well? I'm considering the hardness of the plaster in relation to aerated concrete. I know gypsum plaster can be used indoors for minor repairs, but can it be applied so thickly and on an outer wall/outside? Is it possible to repair with a temperature around zero degrees with a cold additive, or should I wait a little longer? I'm quite bewildered by this. Sigh. If any of you know, I would be very grateful! Thanks in advance!
I am planning to remove a ventilation pipe with an associated fresh air vent that is located in the outer wall. The wall is made of aerated concrete with a layer of plaster on the outside. I keep googling but only find low-alkaline plaster mixes that can be applied in thicknesses of just a couple of centimeters. That doesn't work so well for a larger hole. Mine will be just over 20-25 cm. Do you have any tips on what might be suitable? Is house fix the way to go? Maybe too hard for it to turn out really well? I'm considering the hardness of the plaster in relation to aerated concrete. I know gypsum plaster can be used indoors for minor repairs, but can it be applied so thickly and on an outer wall/outside? Is it possible to repair with a temperature around zero degrees with a cold additive, or should I wait a little longer? I'm quite bewildered by this. Sigh. If any of you know, I would be very grateful! Thanks in advance!
Hello,
I started a thread myself regarding the repair of aerated concrete, missing solid segments, etc.
In summary, Finja sells a repair wall product that is quite expensive but does the job for a moderately sized hole. I used about 4 bags. Not sure about the thickness though. 25 cm deep might be more than it tolerates; I used it for less drastic cavities.
Otherwise, I would recommend doing what I did in the end; concrete. It bonds well with the aerated concrete based on my experience.
Granted, I did cast the aerated concrete walls with a 5 cm thick concrete layer afterwards anyway to get a nice strong wall and a good measure against potential radon, but Finja concrete and aerated concrete worked well until that point.
I started a thread myself regarding the repair of aerated concrete, missing solid segments, etc.
In summary, Finja sells a repair wall product that is quite expensive but does the job for a moderately sized hole. I used about 4 bags. Not sure about the thickness though. 25 cm deep might be more than it tolerates; I used it for less drastic cavities.
Otherwise, I would recommend doing what I did in the end; concrete. It bonds well with the aerated concrete based on my experience.
Granted, I did cast the aerated concrete walls with a 5 cm thick concrete layer afterwards anyway to get a nice strong wall and a good measure against potential radon, but Finja concrete and aerated concrete worked well until that point.