Raised Concrete Patio Drainage
A self leveling cement may reduce the standing water but if the pad has no wire mesh or rebar it may continue to settle. I would acid etch the surface and rinse then use the self leveling cement . after that I would probably epoxy coat the entire surface to try and seal it. the more water that gets into the cracks the more it will settle. I use a 10-30% Muriatic acid and water solution. Remember to always add acid to water. Muriatic acid can be purchased at most home stores and pool supply stores.