1) Extra sturdy 2) Industrial strength 
[G.I. Joe] Heavy Duty is a fictional character from the G.I. Joe: A Real American Hero series of toy lines, comics and cartoons. Heavy Duty is the G.I. Joe Team`s heavy ordnance specialist. He is described as being unafraid of any situation despite heavy enemy fire. He is also the cousin of Roadblock, and shares the same passion for cooking...
Relatively new type of road base and base course, using harder binder and increased filler content.
[adj] - designed for heavy work
adjective designed for heavy work; `a heavy-duty detergent`; `heavy-duty gloves`