Presentation by Brandon Milar, P.E., Technical Director, California Asphalt Pavement Association (CalAPA) to the Transportation Research Board 98th Annual Meeting, Jan. 13, 2019 in Washington, D.C. Event No. 1068. Presentation No. P19-21237. Topic title: Contractor Experience with Smoothness Specifications
5. Asphalt Concrete
Medium & Coarse Gradations
Binder: AR & PBA PG
Method & Density
5
2006 2010 2015
Hot Mix Asphalt (HMA)
3 Construction Processes
(Method, Standard & QC-QA)
Superpave
Gyratory & Hamburg
6. Pre 2012:
California Profilograph
Straightedge
2012 and beyond:
Inertial Profiler
Straightedge
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7. TheTravelling Public Gets It!!!!
Provides a comfortable ride
Lasts longer
Stays smoother longer
Is safer
Saves money (pavement and vehicle repairs and fuel
economy)
Is better for the environment
9. Head of Material on Screed
Paving Speed
MixTemperature
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10. Reference a portion of
pavement that is smooth
Reference a smooth, cold
planed surface that was cut
with an averaging system
Don NOT reference a cold
planed surface that
Trust the Equipment
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12. Use a good control system (i.e.
an averaging system) on the
existing surface
Following an existing rough
surface at constant depth will
transfer the roughness to the
bottom of cold planed surface.
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13. Proper maintenance of
mechanical systems
Proper maintenance and
replacement of cutting tools
and blocks
Smooth transitions in and out
of cuts
Clean the milled surface
Do NOT stop drum in the cut
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22. 22
0.20' Mill and Fill with SAMI
75 MRI
Existing Breakdown
> 85 66%
> 135 31%
> 165 14%
> 200 7%
> 331 0%
0.1' Mill and Fill
75 MRI
Existing Breakdown
> 85 17%
> 135 1%
>164 0%
23. Specification applied a simplified requirement for ALL
pavement conditions.
Pavement design may or may not address the existing
smoothness condition.
Specification assumes that design is appropriate for existing
pavement smoothness
Specification use and enforcement inconsistent from project
to project.
The above leads to bidder confusion, disputes, and claims
24. Recent revisions tried to “bite off more than it can
chew.”
No data to support limits
Lack of incremental approach to improvement
Significant and unnecessary risk placed on the
contractor.
25. Many Claims and Disputes
Large Losses - Both Contractors and State
26. Increase gas tax funding – DOUBLED!!!
Requires performance criteria in 10 years
Includes Statewide Network SmoothnessTargets
PMS triggers for roadway correction
Deformation
Cracking
SMOOTHNESS!!!
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27. In a partnered/collaborative environment
Development of new specifications should be “data-driven.”
Specifications should be uniform and consistent in
application and acceptance.
Specifications should be “street ready.”
28. Rehabilitation of Asphalt Concrete Pavements: Initial
Evaluation of the SPS-5 Experiment—Final Report
FHWA-RD-01-168
“The age of the overlay, condition of the pavement before
overlay placement, and surface preparation or milling depth
were factors found to be important relative to the IRI values.
The IRI values of the overlay were found to be lower for the
overlays placed over pavements in the fair category and
when the existing surface was milled before overlay.
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31. Use an equation to relate paving expectation for a single lift opportunity
based on an existing pavement smoothness.
MRIt = 0.3 * MRI0+35
MRIt = 0.1 mile segment MRI target value
MRI0 = existing pavement MRI for the 0.1 mile segment
▪ For each opportunity, re-apply the equation for each opportunity (i.e. for 2 opportunities
MRIt=0.09*MRI0+45.5)
32. Example: Single lift overlay
Use the equation: MRIt = 0.30 x MRI0 + 35
MRI0 MRIt
135 75
165 85
210 98
250 110
33. Example: “Mill & Fill” with 2 lift overlay
Use the equation: MRIt = 0.09 x MRI0 + 45.5
MRI0 MRIt
135 58
165 60
210 64
250 68
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All 0.10 mile sections above 135 MRI Baseline – Target % Improvement
All 0.10 mile sections at or below 135 MRI Baseline – Target 75 MRI
Target MRI is 83.6 in/mi
41. 0.20' Mill and Fill with SAMI
75 MRI
Existing Breakdown
> 85 66% Table 75
> 135 31% % improvement
> 165 14% % Improvement
> 200 7% % Improvement
> 331 0%
0.1' Mill and Fill
75 MRI
Existing Breakdown
> 85 17% Table 75
> 135 1% % Improvement
>164 0%
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42. Pilot Projects in 2019
Train designers on process to evaluate projects for smoothness
and incorporate corrections
Train DOT REs on specification administration
Train contractors on specification requirements and construction
BMPs.
Collect field data and refine equation and specification
requirements.
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