Thank you all for your input regarding my question on a long cantilever on exterior concrete deck.
Deck is competently exterior, no door threshold to consider. Deck is relatively small, 25'long x 15' cantilever and 10' back span. It is on a bluff above the ocean in Malibu, so limited rainy season but [per one to morning fog. Architect wants concrete surface exposed to view - possibly acid washed or sand blasted to expose aggregate, so there will be no hiding cracks.
I have a concern about the concrete acting like a sponge and soaking up moisture during rains. I am looking into bonded pt, epoxy rebar for temp bars (or possibly main steel if job is too small for the pt guys) and w/c of 0.45 was suggested as a couple means of protecting rebar. Also thinking about adding Xypex to mix. Any other ideas to protect rebar if concrete is the final finish?