Blood Concrete

Concrete from buildings or structures that has crushed people to death, with the entire pile of rubble hastily grounded down to make new roads or bricks, without regard of the bodies inside the wreckage.

While definitely not a common occurrence, it has been known to happen during devastating wars, or massacres.

That new road was paved with blood concrete. It contains my Uncle Joseph, my friend Thomas, and many others I don't know of.