I have never seen tar applied directly to concrete as a roofing system.
You need much more information for an intelligent answer.
I suspect that you have a flat or low pitch roof. I doubt that it is a concrete roof. It is probably wood framed, plywood sheathed, and roofed with a 3 or 5 layer asphalt roof. It probably has stone or cinder ballast.
If you cannot understand any of this conversation, you need to contact a local roofing company for advice. Talk to more than one company to see if they both see a similar project. There are many solutions, too varied to address here.
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