Hey Rick, how are you?

"Concretan civilization" refers to the fact that a huge proportion of what's visible at Knossos is Sir Arthur's "reconstitution" in reinforced concrete, based to a large degree on speculation, wishful thinking, blithe assumptions, and overconfident extrapolations from things like the Town Mosaic. Same thing goes for the "reconstructions" of the Knossos frescoes, the "Snake Goddesses", and Sir Arthur's overall reconstruction of Minoan culture. You can't fault the man for his enthusiasm, nor for being a man of his times, but it certainly didn't make life any easier for post-Evans scholars of ancient Crete.