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Using IRI for Construction Smoothness Acceptance in Missouri
John P. Donahue, P.E. CM Liaison Engineer
North Central Asphalt User Producer Group Meeting February 20, 2014
PI to IRI
MoDOT transitioned from using the profilograph index (PI) to the international roughness index
(IRI) for construction smoothness acceptance in 2013.
a) Multi-lift asphalt construction
b) Concrete pavement construction
c) Combination of surface planing (diamond grinding, milling) and single lift asphalt construction
d) Single lift asphalt construction
Applicable Pavement Types
Mix Type Requirements
• Superpave (SP) – IRI
• Bituminous pavement (BP) – IRI
• Surface level (SL) – Straightedge
Mix Quality
• All inertial profilers used for construction acceptance must be certified annually at the MoDOT certification site.
• Operators of inertial profilers shall hold
current certification issued by the Technician Certification Program (TCP).
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Inertial Profiler Requirements
IP Certification Procedures
• ‘Ground truth’ - certification test section at Linn State A/P measured with a reference profiler (SurPro®).
• Real time reference profiles for each day’s testing.
• NO filters allowed!!
IP Certification Procedures
• AASHTO R 56-10 – Recommends up to three separate certification
test sections : smooth, medium-smooth and medium-rough
o Forced to stick with existing single test section (~ medium-smooth) for 2012 certifications, but will try to add smooth section in future.
IP Certification Procedures
• AASHTO R 56-10 – Recommends 10 runs for each test section o MoDOT requires 5 runs per wheel path (MnDOT
procedure). – Recommends accuracy and repeatability checks o MoDOT uses AASHTO recommendations
oRepeatability agreement score of 0.92 or higher oAccuracy agreement score of 0.90 or higher oProfile length within 0.2% of reference.
Certification vs. Calibration
• MoDOT will NOT calibrate or ‘fix’ IPs at the certification site.
• IP owner will not be able to adjust filters to match desired results.
• (used to) –Compute average IRI smoothness –Locate areas of localized roughness
(ALR)
ProVAL Software
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ProVAL Ride Analysis
o Section – A day’s paving. Normally begins and ends at construction joints. Other logical termini such as bridge ends may also define limits.
o Segment – 0.1 mile (528 ft.) length. • If the last segment is greater than 250 feet and less
than 0.1 mile, the segment shall be measured as an independent segment.
• If the last segment is 250 feet or less, the profile for that segment shall be included in the evaluation for the previous segment.
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Smoothness Increments
• Inertial profiling is applicable to the surface of all the following: a) Mainline paving b) Auxiliary lanes, turning lanes and ramps for
projects consisting of more than 0.5 mile of total profilable pavement.
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Inertial Profiling Areas
• Bridge decks, bridge approach slabs and concrete approach pavements.
• Pavement on horizontal curves with a centerline radius of curve less than 1000 feet and pavement within the superelevation transition of such curves.
• Pavement on vertical curves having a “K” value less than 90 and a length less than 500 feet.
• Pavement width transitions. • Fifty (50) feet in the direction of travel on each side
of utility appurtenances such as manholes or valve boxes.
Inertial Profiling Exceptions
• Fifty (50) feet in the direction of travel on each side of intersecting routes with special grade transition.
• Shoulders. • Interruptions designated by the engineer which
provide independently placed sections shorter than 50 feet.
• The last 15 feet of any section where the prime contractor is not responsible for the adjoining surface.
• Pavement next to existing untreated lanes. 17
Inertial Profiling Exceptions
• In addition to the listed exceptions, profiling may be waived by the engineer if staging of the overall project; such as multiple entrance lane gaps, lane staging, etc.; affects the normal paving operation, or if multiple profile exceptions continuously exist on a large portion of the same roadway. Upon waiver, exempted areas shall be checked with a 10-foot straightedge.
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Inertial Profiling Exceptions
• Any pavement surface not measured with an inertial profiler shall be measured with a rolling 10-foot straightedge.
• The straightedge path in the longitudinal direction for driving lanes will be located 3 feet from the outside edge and for shoulders will be located in the center.
• Shoulders paved integrally with an adjacent driving lane do not require straightedging.
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Longitudinal Straightedging
• Any variations in the longitudinal direction exceeding 1/8 inch (1/4 inch for shoulders) in 10 feet are marked for correction in a manner approved by the engineer.
• Regardless of the smoothness measurement method used, the engineer may check any location of the paved surface with a straightedge for unacceptable bumps or low spots.
Longitudinal Straightedging
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• The MoDOT engineer randomly checks driving lanes for variations in the transverse direction with a 4-foot straightedge.
• Any variations in the transverse direction
more than 1/4 inch are marked for correction in a manner approved by the engineer.
Transverse Straightedging
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Full Depth Pavement and Multi-lift Overlays
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• The contractor performs quality control (QC) testing on all eligible profiling areas and provides
• daily section smoothness data • completed project ProVAL® reports.
• Reported IRI for each segment is the average
of both wheel paths.
Payment Schedule
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For posted speeds over 45 mph
For posted speeds of 45 mph or less
• MoDOT performs quality assurance (QA) testing on 10 percent of the total project lane miles
• The contractor (QC) IRI value for the average of both wheel paths in each segment must be within 8 inches/mile of the MoDOT (QA) value.
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Quality Assurance Testing
• Areas of localized roughness (ALR); defined as any length of pavement, having a final posted speed greater than 45 mph, with a continuous section 25-foot average IRI of 125.0 inches/mile or greater, or any length of pavement, having a final posted speed of 45 mph or less, with a continuous section 25-foot average IRI of 175.0 inches/mile or greater; must be corrected.
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Areas of Localized Roughness
• After correcting ALRs, additional correction may be necessary to reduce any profile segment in a pavement with a final posted speed greater than 45 mph, to an average IRI of 80.0 inches/mile or less; or reduce any profile segment in a pavement with a final posted speed of 45 mph or less to average IRI of 125.0 inches/mile or less.
Further Corrections
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• Corrective action to eliminate ALRs and improve the average IRI is accomplished by diamond grinding or other method approved by the MoDOT engineer.
• Contractor can grind entire section to get in bonus.
• Contractor can grind entire segment to get 100% pay.
Method of Correction
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• A combination of diamond grinding or milling and a single lift asphalt overlay.
• Same criteria as multi-lift overlays, except – ALR maximum is 175 inches/mile for pavements
of all posted speeds and – Corrective grinding is only allowed for ≥ 1 ¾”
overlays.
Multi-Treatment (Mill/Fill) Overlays
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• 20 percent unit price reduction for marred areas, including ground surfaces.
• The deduction is applied to an area of pavement extending from edge of the pavement to a longitudinal joint or between longitudinal joints in that section of pavement affected for a minimum length of 10 feet.
Marred Surface Deductions
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• Prior to performing any resurfacing work, the contractor profiles the outside wheel path.
• This control profile serves as the baseline for calculating percent improvement for the project.
• After resurfacing, the contractor profiles the outside wheel path again.
Single Lift Overlays
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Percent Improvement Payment
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• 100 % pay after correction to 0.0 or greater. • Segment ≤ 60 inches/mile before and after
overlay gets 100% pay, regardless of percent improvement.
• Any dispute between the engineer and contractor regarding IRI QC/QA comparisons that cannot be settled at the project level is arbitrated with the MoDOT reference profiler.
• The results of the reference profiler are binding for the engineer and the contractor.
Dispute Resolution
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