The main advantages of prestressed concrete (PSC) are:
Smaller Section Sizes
Since PSC uses the whole concrete section, the second moment of area is bigger and so the section is stiffer:
Smaller Deflections
The larger second moment of area greatly reduces deflections for a given section size.
Increased Spans
The smaller section size reduces self weight. Hence a given section can span
further with prestressed concrete than it can with ordinary reinforced concrete.
Durability
Since the entire section remains in compression, no cracking of the concrete can occur and
hence there is little penetration of the cover. This greatly improves the long-term durability
of structures, especially bridges and also means that concrete tanks can be made as watertight
as steel tanks, with far greater durability.