Steven McCarthy, in Visible Language: "'Dirty concrete poetry' was a term in circulation between McCaffery, his contemporary bp Nichol, and others in the Toronto-based poetry scene of the 1960s and ’70s. It referred to the grittiness, the layering, the messy expressiveness of McCaffery’s poetical typestracts"
poems "with amorphous visual shape and complex and involute arrangements of linguistic elements. In dirty concrete there can be no immediate to the whole, only a cumulative interpretation gained by painstaking labor” (Lori Emerson, in "The origin of the term 'dirty concrete poetry' (en route to
digital D.I.Y.)")
https://talonbooks.com/meta-talon/
the-origin-of-the-term-dirty-concrete-poetry-en-route-to-digitaldiy (now 404)