What Is an Acceptable Surface to Be Resurfaced?
Small plastics shrinkage cracks or crazing cracks can be covered by the polymer prime coat and base coat of the resurfacing material.
Larger cracks must be repaired. See a pictorial tour of this process.
In any case, the underlying concrete for a resurfacing project must be sound. It is not feasible to resurface concrete that is heaving, has severe cracks, or is damaged due to freeze/ thaw damage. Resurfacing will not solve underlying soil problems.
Read about types of repairs that can be done to concrete: Basics of concrete repair and troubleshooting