pt slab exposed v. protected

huangyhg

pt slab: exposed v. protected?
hello fellow engineers,
my office is reviewing a pt slab for another engineering office.
the project is townhomes and a courtyard over a pt deck with parking below.
the other engineering office is only using 3/4" cover instread of 1" (for weather exposure).  i assume they are going to justify it by saying that they have waterproofing, tile, sloping grout on top of the pt.  is that credible?
please let me know what you think.
thank you,
mike
waterproofing on concrete to me means that it is not exposed to earth or weather per aci.
     depending on the climate at your location and whether or not the local roads are de-iced using road salt or is near salt water, the corrosive environments clause of 7.7.5 should be considered.  this increases the minimum reinforcement cover to two inches for slabs.  the lack of external walls enclosing the slab seems to be "exposed to weather" even with a topping or tile cover.  the bottom side will experience temperture and humidity changes reflecting ambient conditions and the the topped side will be partially moderated by the insulation value of the tile or topping.
and for fire-protection?  what is the cover required for that?