The matrix and the firmness of the AAC products are made due to autoclaving.
It is possible to form foamed or aerated concrete without autoclaving but the properties are going to be very bad. Of course, such products will contain mostly cement.
The mechanical strength will not be very high and through the drying, the shrinkage is going to be excessive.
Technically, such a product will start cracking by itself when it approaches equilibrium moisture content after a couple of years.
In the case of ordinary concrete products, there are no shrinkage troubles during the drying operation. But in foamed or aerated concrete the mixture is air and if manufactured without autoclaving, drying shrinkage will cause cracking.
The calcium silicate hydrates formed during autoclaving is more stable than the one formed of cement at room temperature.
Autoclaved products have low shrinkage.
Cement will need four weeks to achieve its final strength at room temperature whereas, autoclaving takes only 12 hours. to get desired strength.