By Robert J. BlightProject Engineer

Bureau of Materials

Remove Deteriorated and Distresses Pavement (to a specified depth)

Improve Cross-Slope Achieve Specified Grades Provide a Uniform Surface Texture to

Facilitate Compaction of HMA Provide Best Opportunity for Achieving the

Ride Quality Requirement

Excavation Maintain Overhead Clearance Correct Ponding and Drainage Maintain Curb and Gutter Staged Construction

Need enough of cores to determine the consistency of the existing pavement

Establish the “most” reasonable milling depth

Provide thickness of the layers Determine depth of “Top Down” cracks

Need to remove the entire layer to avoid scabbing

Need to remove reasonable amount of the deteriorated pavement

Need to remove the entire layer to avoid scabbing

Need to remove reasonable amount of the deteriorated pavement

For every operation (or opportunity) the IRI was expected to be improved by 30%◦ Milling = 30 % improvement of IRI◦ Each subsequent operation (each paving lift)

expected 30% improvement of of IRI

Determination of the Target IRI is more complicated

30 % improvement is no longer used in determination of Target IRI

Many other factors involved that affect the target IRI

THE POINT IS THAT EVERY OPPORTUNITY FOR SMOOTHNESS (MILLING) IS IMPORTANT

Equipment◦ Self-propelled with variable operating speeds

capable of removing pavement without using heat◦ Automatic grade controls◦ Stringline or ski type reference system

Ski must be minimum of 20’ length◦ Teeth should be replaced if dislodged, broken or

unevenly worn

Construction◦ No ride quality requirement◦ Texture requirements, but they are not typically

checked Striations must be within ±1” in 200’ of line parallel

with the center of the traveled way Striations not to exceed 3/8” depth Milling depth within a tolerance of ± ¼” If opened to traffic, no drop-offs to exceed 2”

Equipment◦ Self-propelled with variable operating speeds and

equipped with cutting drum specifically designed for milling pavement to close tolerances

◦ Drum must have 2 wraps of flighting with bolt-in blocks that accept 3 or 4 teeth on the wear side of the flight Second wrap of flighting must trail the first by 180

degrees Teeth spacing of 5/16” (±1/32”)

◦ Cutting radius of the drum within ± 1/32”

Construction◦ No ride quality requirement◦ Texture requirement, but typically not measured

Striations must be within 5/16” center to center Striations not to exceed 1/16”

Indiana DOT◦ Macrotexture

Requirement measured by Sand Patch Test using glass beads (ASTM 965)

◦ Not complicated◦ Data shows

improvement in HMA densities due to improved working platform

Georgia DOT◦ Ride quality

requirement for milled pavements if traffic is allowed prior to overlay IRI < 75 in./mi. for

Interstates IRI < 85 in./mi. for all

others

Industry has requested to allow traffic on milled surfaces

If NJDOT allows traffic, we will require “End Result” specifications◦ IRI◦ Macrotextureor◦ Combination of IRI and macrotexture

Micro-milling specification will have “End Result” requirements

Contact Info.:Robert J. BlightProject EngineerNJDOTBureau of MaterialsPhone (609) 530-4445robert.blight@dot.state.nj.us