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Adding fiber to a concrete mix provides some tensile strength, but it doesn't replace rebar or welded wire fabric. If bar or mesh is used, placement is critical and should be 1" clear from table top. As concrete cures, and it never stops curing, it shrinks and the edges want to curl up and deform into a smiley face configuration, exaggerated. That's where the steel reinf resist the tension from shrinkage. Controlling your curing process helps resist surface cracking too. A water soaked beach towel place atop the table would be a good idea for 24 hours. A lower compressive strength concrete mix, say 3000 psi, would be easier to work with and result in less cracking than a 4000 psi or higher mix. I doubt you're going to have a compression problem on a table top anyway, good luck.
What is weight of the table when finished? great job..