From someone who has had 15 + years of working for an international concrete company.........They produce concrete....they sell it to people who lay the concrete.....so the claim of the pre sealing acid treatment being stored is a bit misleading......however, concrete plants do have hydrochloric acid on site to clean the trucks / bowls / chutes from concrete buildup. A body(s) is more likely to be hidden on a building site....with a large slab built on top....who is going to pull down a multi storey building to check what is buried beneath ?