In the living area, the concrete is impregnated and in the garage sealed with water glass.
What do you use for the impregnation? After a long research, I have now decided on Keim products for our stairs. Clean with the concrete quick cleaner (although they were wrapped in wood during the construction period, it got wet several times), then Silangrund and simply just the fixative of the Concretal glaze on top. We skip the glaze itself because we don't want to change the color. I hope it will be maximally matte and invisible...
That sounds more like sealing?! I will only polish the steps (currently also wrapped) very finely so that the dirt is gone and then impregnate them. I don't know exactly which product I will use for walls and stairs yet. Garage with [Wasserglas] (sealing) is set. I will then test different impregnations in the technical rooms and use the winner for the living areas as well.
Our exposed concrete staircase also came as a prefabricated element and was covered for a long time. It has withstood the construction phase well, but I would like to clean it again. My wife thinks it is fine as it is. We'll see. The staircase is impregnated from the factory. That works quite well too.
Water glass is tried and tested for sealing or preventing sandblasting. It is also used for basement and wall waterproofing or for fire protection. Cheap, simple, and effective. There is no mechanical stress on the walls anyway. Potassium water glass is the optimal choice in terms of price/performance.