Hey all, this  slab was poured a few months ago and rained on alot. it
was finished smooth with a power troweler. can anyone explain what
caused the black color. I know it was water but some of the slab has it
and some areas do not. I plan to sand the slab some what coarse (50/120)
and would prefer coating it but a bit concerned about the coating
bonding . Thanks

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