fire resistance for hollowcore slab
 

fire resistance for hollowcore slab
one of my current projects is the remediation of a transformer vault to increase the fire resistance rating to 3 hours.
the roof of the vault is constructed of hollowcore slab; thickness not yet determined, but likely 8". also cover to strand not determined, could be 1" or less. in any event the slab does not have a 3 hour rating.
is anyone aware of a bonded surface or intumescent coating that can be used to increase the frr? i'll be in contact with coating suppliers to find out what's available. at this point i have no idea of the load capacity of the hc slab.
any suggestions about remediation?
dik