HMA Base Courses

[Roadwork]

Looking for comments/feedback on a contractor requested design change for the HMA base course on a 12,000 ADT roadway. They want to use a 3/4" mix, instead of the specified 1" mix for the base course.

 

[Ron]

I'm confused by your terminology. Do you mean a nominal coarse aggregate size when you're refering to 1" or 3/4"?

If so, it makes no difference for the base course...in fact, most HMA base courses are even finer than 3/4" nominal.

If that is not what you meant, please explain.

 

[ACtrafficengr]

NYSDOT specifies 1.5" max aggregate for base, 1" max or 3/4" max for binder, and 1/2" max or 3/8" max for top.

Regarding binder, NYSDOT's Comprehensive Pavement manual states "The 25.0 mm size should be used for pavements with 20 year ESAL counts over 10 million.

https://www.nysdot.gov/divisions/engineering/design/dqab/cpdm/repository/chapter6.pdf,

page 6-7.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928