what does artisanal concrete have to do with collectively forgetting how to make a giger counter?

Isn’t this no longer true? I’ve seen many experimental archaeology documentaries that use a recipe that uses pozzolanic ash and rock from volcanoes in Italy that they show to create the same properties found in Roman concrete. We don’t make concrete with it now because the supply is too limited and the expense of mining it would be greater than making portland cement.