Use ground contact (GC) rated pressure treated wood. Don't skimp by using untreated wood or even above-ground; ground contact or bust! In addition to its rot resistance it is generally less susceptible to damage from bugs since it has undesirable chemicals.
Ground-contact pressure-treated wood:
- Ground-contact pressure-treated lumber can be used either above ground or in contact with the ground.
- Has twice the level of chemical retention and protection compared to above-ground treated wood.
- Must be used when lumber is less than 6 inches from the ground or has poor ventilation.
- Must be used for applications where wood is difficult to maintain or replace.
If you use pressure-treated and there is seldom standing water on the concrete then that deck will easily outlast your lifetime.
If you wanted to really overkill things then you could cut PVC shims from trim board and glue/tack them to the bottom of all your joists so that they float 1/2"-1" above the concrete.
Flashing tape could also work but my fear is that it has the potential to lock moisture into the wood.