Invent recycled building material from concrete, plaster, paint, wallpaper, and stone.

My intention is nature conservation. Our civilization only builds with raw materials that have already been used before.

Since there are more and more people, the consequence is that more and more houses, buildings, and infrastructure of all kinds are needed. For this reason, the recycling calculation doesn't add up. Because you will always need more material than is already available.

Otherwise, there is no need to look for possibilities. The methods exist and are also applied. The rubble is not pressed into new blocks but used in road construction, etc., since the same raw materials are necessary there as well.

And it is much more sensible to use demolished buildings as a load-bearing base instead of taking new raw materials for this purpose. It would be totally absurd to take fresh, new bricks, etc., and then bury them on a large scale under the surface layer. I assume everyone agrees with that. And yes, road construction is desired. Even militant cyclists are demanding more and more of it.

The topic of recycling has already reached construction product manufacturers. There is a lot of research being done, but some of it has already been incorporated into current products. The devil is in the details. This goes hand in hand with modified formulations and new production processes. Next come new approvals and much more. The biggest sticking point is that the price of the product must not rise to an exorbitant level. Depending on the product, reaching market readiness can quickly cost six figures or more!

1. Is there a machine that grinds the stuff so finely? The regular crushers are not sufficient. 2. The cost of the crushers was so expensive that removal and recycling, reinstalling was cheaper. 3. Pollutants are tested from 500 cubic meters in Bavaria. The demolition contractor was most worried not about the cowshed, but about the walls from the post-war period. Back then, everything was baked into stones. And that was also the problematic pile. Not every landfill accepts every pollutant class. You want to bake everything in. Building materials must meet standards. This would have to be checked anew for every house (since different rubble is present). 4. Where is the grinding, baking, and shaping done? Transport Ecologically, closing building gaps, densification, careful separation during demolition, building as small as possible, and designing outdoor areas close to nature are advisable.

My intention is nature conservation. Our civilization only uses raw materials that have been used before.

On the one hand, that does not answer my question whether you are asking this just academically or if you are facing a concrete demolition project. On the other hand, you should google "Trümmerfrauen" and also first acquire basic knowledge about recycling (and also consider the ecological footprint of the respective methods). The crucial point for the difference between re- and downcycling lies in the purity of the types of materials fed into the process; and in this sense, your hoped-for building material would have the drawback of inhomogeneity – it would unfortunately only be possible to re-fractionate it by downcycling next time with high (including energy) effort. Furthermore, due to its vaguely definable composition, it could not be entered into any U-value calculators and practically could not be used for any building subject to energy saving regulations. It would therefore only be a building material for sheds and detached garages. On closer examination, you would thus get pretty much the opposite of what you hoped for: solution planned, problem created :-(

Okay, thanks for the insight into the recycling business. I'll stay away from that, and those who know what they're doing will handle it.

I'll stay away from that and let those who know what they're doing handle it

That would be wrong because they do not follow your concern in the way you intend. You can recycle the material from your demolition - that's why I advised you to google the "Trümmerfrauen" - and you can reuse stones freed from mortar as stones and so on, just not in ground and newly mixed form, because that would be of little use in terms of your intention.