Crazy idea; burning portland cement based concrete in a lime kiln?

This isn't something I'm looking to do in the near future, but I've been researching lime burning. It is an interesting industrial process that can be done on small scale.

I started to wonder what would happen if a kiln was loaded with chunks of portland cement-based concrete instead of limestone. I realize portland cement is a different material than lime-based cement. But I was thinking that most portland cements contain a portion of lime, which would reburn into quicklime; many portland cement concretes contain limestone aggregate, which would be burnt into quicklime; and the fine aggregate in concrete is sand, which is needed in lime mortar or lime plaster in any case. The material is a widely available waste product that doesn't have to be mined. Any non-burnable aggregate could be screened out of the final product, which has to be done with burnt limestone in any case.

What I can't find any information on is what happens to portland cement when it is reheated. Would it remain as an inactive fine "sand-like" substance? Would it change into a different, reactive form? I assume that it can't just be reactivated into portland cement, or concrete manufacturers would already be doing this.

I had a look around my sources of information and can find nothing.
My guess is that wiyh the temperatures involved, 1400C I imagine a permanent change will have taken place with the ingrediants.

I was thinking some places recycled concrete like this but I may have just imagined it like you, lol. I'm pretty sure it can be used as part of the mix, but some fresh stuff needs to be added too.

I have used recycled, crushed concrete.
When laid on a car parking area there is a small amount of resetting of the product, caused I have heard cby remnant cement, but it would not be hard enough for a suspeneded slab though.

I understand a major part of the issue with Portland cement versus lime is that cement must be burned at a much higher temperature, thus taking significantly more energy to produce.

Recycling concrete generally involves crushing it and using as (part of) the aggregate in new concrete, thus saving the mining of gravel for the new concrete. Uses such as compactable fill for driveways would be another good way to recycle old concrete.

As I understand it, if you heat a Portland cement product above a certain temperature it breaks the chemical bonds formed from mixing with water. With all of the other stuff in typical concrete, I don't know if heating everything that high causes some of the other components to break down and some percentage of that could form undesirable bonds. That's also assuming nothing else was absorbed by the concrete while in use since it acts lie a sponge.

The other problem is that concrete can hold sizable amounts of unbonded water. You would have to slowly heat it up to drive that water off first to prevent it from more or less exploding. I have heard of people making quick rocket stoves out of concrete and not just having it crumble or cause minor spalling, but sometimes fail catastrophically. Water expands around 1700 times in volume as it turns to steam. This is bad enough when out in the open, but putting a bunch of it in a sealed system could be very dangerous. I'd imagine between the extra care needed to avoid that and the potential danger of a mistake makes it unattractive on a large scale. It might be less dangerous when crushed, but at that point it is probably cheaper to use it as aggregate.