In addition to some "bycatch" (seeds of non-barley species) I found a flake of particle board in my sack of Great Western 2-row. Their malt is usually super-clean. That concrete could play hell with one's mill rollers and, perhaps, raise the pH of the mash a bit.
i was wondering if the concrete could raise the mash some too. there was a LOT of concrete in it. i was shocked. i wonder if their generations old malting floor is crumbling?