update on pavement smoothness in california
TRANSCRIPT
Update on Pavement Smoothness In California
CalAPA Fall Asphalt Conference & Equipment Expo October 27, 2016Don Matthews, PE
Pavement Recycling Systems, Inc.
California’s Smoothness Transition Before 2012, pavement
smoothness was measured using a California profilograph and straightedge
After 2012, pavement smoothness is measured using the inertial profiler and straightedge
Ride Comfort – Depends On: Road Roughness
Vehicle Response to the Road
Human Response to Vibration
Profilograph and Inertial Profiler
Inertial Profiler and Subsequent IRI Calculation
Indirectly Considered via IRI
Quarter Car (Golden Car) Filter
©Copyright the U. of Michigan
International Roughness Index (IRI)Provides a standardized value that is determined by obtaining an accurate measurement of the profile of the road
Then processing that profile through an algorithm (ProVAL) that simulates the way a reference vehicle (golden car – represents 70% of vehicles) would respond to the roughness inputs in a single wheel path
No One Debates the Benefits of Smooth Pavements
Smoother roads:
Provide a comfortable ride Last longer Stay smoother longer Are safer Save money (pavement and vehicle
repairs and fuel economy) Are better for the environment
In Fact:
So Why All the Issues?
Many Claims and Disputes
Large Losses - Both Contractors and State
In a Word:
Ignorance
By Most Everyone
To Help
Industry and Caltrans together held a Smoothness Forum 9/28/15
A Smoothness Subtask Group Was Formed• Working Group - Data Collection/Analyses, Design
Guidance and Specification• Working Group - Best Paving Practices• Working Group - ProVAL Training and Smoothness
Corrections
Profilograph Specification• Profile Index of 2.5 inches per 0.1 mile• Must Grinds – Localized roughness of 0.3 inch or more in 25 feet
Inertial Profiler with IRI Specification• Mean Roughness Index (MRI) – 60 or 75 in/mi depending on depth of HMA• Area of Localized Roughness (ALR) – 160 in/mi localized roughness based on a
25 feet sliding scale
They Seem Similar
What the Specification Numbers Meant
Determined That Few Understood:
Concept Maybe Numbers No!
Few Understood:
What it took to achieve the new smoothness requirements during construction
What best paving practices are really required for smoothness
The Killer Phrase -“I am not worried about it. I have been paving for 30 years” Get out the checkbook!
Consistency - Head of Material on ScreedConsistency - Paving SpeedConsistency - Mix Temperature
Best Paving Practices = Consistency!!!
Screed Control – ReferencingWhat is referenced has a major impact on smoothness
Longer and smoother the reference, the smoother the pavement
A smooth cold planed surface that was cut with an averaging system could be a good reference surface as opposed to a rougher shoulder or adjacent lane
However, if the cold planed surface delaminates another surface should be used
Once a good reference line is set trust the equipment
.
ReferencingWhy Correct Here?
If Paver Will Reference Here?
Best Paving Practices Training Available
Joint Working Group on Best Paving PracticesIs nearly complete with training moduleExpected out by end of the year
CalAPA’s ½ Day Training ClassPAVEMENT SMOOTHNESS ESSENTIALS -- NEW SPECIFICATIONS, TECHNOLOGY & BEST PRACTICES
Also Realized Few Understood:
If smoothness could be achieved for a given roadway condition using standard design strategies
No Consideration of Roadway Location or TypeLittle Consideration to Existing Roughness
TYPES OF ROADSBoth Mill and Fill of 0.10’
Both Have a Final MRI Requirement of 75 in/mi
The roadway on the right will likely take much more pre-paving correction and effort then the left
Existing SurfaceMRI (in/mi)
New SurfaceMRI (in/mi)
300 120200 90150 75120 6590 6060 45
*Based Upon One Smoothness Opportunity Using Best Paving Practices
As Part of the Smoothness Working Group Industry Provided Reasonable Expected Improvement ValuesFor Caltran’s Consideration
Additional Rehabilitation Line Items Would Be Provided If Existing MRI “Too Rough” For Primary Design Strategy
Existing Pavement Grinding or Cold Planing CorrectionsRemovals and ReplacementLeveling Course etc.
Least agreement on this number
Prepave Grinding (Corrections) As a Strategy
Existing Asphalt Surface Prior to Overlay
Existing Pavement Surface
Aggregate Base/Subgrade
Pre-pave Grinding or Cold Planing is a Smoothness Opportunity
HMA OverlaySmoothness Opportunity
CalTran’s Specification – Prepaving “Grinding”
Correct Areas of Localized Roughness HMA >180 in/mi Currently Bid by Day with Extra Days Paid as Determined By RE. Any
Areas Not Corrected, Excluded From Final Smoothness Requirements Should Come with Inertial Profiler Bid Item Overlay’s Only. Not Provided for Cold Planing or CIR
In the Future Pre-construction Profiles with Electronic Files Provided and Prepaving Corrections Bid by the Lump Sum?
Depending on Existing Roughness Corrections May be Necessary Even Prior to Cold Planing
Some Concern Over Interpretations
Law of diminishing return by surface corrections
And Again Why Correct Here?
If Paver Will Reference Here?
Mill and Fill
Cold Planing As A Strategy
Existing Pavement Surface
Aggregate Base/Subgrade
Smoothness Opportunity? Filled HMA Smoothness
Opportunity
Cold Planing a Smoothness Opportunity?
There is a Debate!
Do Agree That It is Not Effective if:Mill depth must be at the specified depth and follow
existing surface Paving operation does not use milled surface for controlGood paving practices are not utilized
Variable Depth Cold Planing Must be UsedFollowing an existing rough surface at constant depth will transfer the roughness to the bottom of cold planed surface. Good control systems such as an averaging system should be used on the existing surface
Variable Depth
Good Cold Planing Practices Must Be Followed:Transitions must be smooth into and out of cutsThe milled surface must be cleaned wellThe drum must not be stopped while still in the cutThe mill’s mechanical systems must be maintainedThe cutting tools and blocks must be maintained and/or
replaced as needed
Appropriate Continuous Speeds Must be MaintainedDo not out run the pattern – It may not be about productionThe texture changes as speed increases
Must Implement Quality Control - Take Pictures of Issues and Use Straight Edge
Pre Milling Post MillingMRI
(in/mi)MRI
(in/mi)Change in
MRI%
Change127 96 31.2 25%120 98 21.6 18%
74 77 -2.4 -3%95 94 1.5 2%83 145 -61.9 -75%96 101 -4.8 -5%77 99 -22.7 -29%88 114 -26.7 -31%80 128 -48.1 -60%78 118 -40.0 -52%86 88 -2.1 -2%64 112 -47.7 -74%65 104 -39.0 -60%90 123 -33.5 -37%63 91 -27.8 -44%72 97 -25.1 -35%
101 96 5.0 5%79 110 -30.4 -38%61 140 -78.8 -129%61 113 -51.5 -84%70 91 -21.2 -30%71 105 -33.3 -47%
123 130 -7.0 -6%72 125 -53.0 -74%81 75 5.3 7%77 107 -30.3 -40%98 106 -8.2 -8%
State project
4” mill depth
Made worse in many cases
Cold Planing Still May Not Improve Smoothness
If delamination occurs the cut depth must be deepened
Paving over a delaminated surface can result in deferential compaction
A delaminated surface will also provide a rough reference line for the paver
Delamination
Existing Pavement Surface
Aggregate Base/Subgrade
Cold In-place Recycling (CIR) With Overlay as a Strategy
HMA Overlay Smoothness Opportunity
CIR
Sort of a Smoothness Opportunity
CIR as an Smoothness Opportunity: Regardless of the existing roadway’s
roughness, using best practices should result in smoothness of the CIR at about 90 in/mi MRI
Using best practices, a 60 in/mi MRI should then be attainable on the HMA overlay
The Smoothness Subtask Group has made the recommendation to raise the CIR smoothness from 75 in/mi MRI and 180 in/mi ALR to 90 in/mi MRI and 240 in/mi ALR, with no change to the overlay smoothness requirements
Finally, Apparently Few Understood:
How to correct the final paved surface for smoothness What equipment must be used How to prepare effective grinding strategies The benefits and limitations of ProVAL
The limitations as to the amount of corrections that can be done by grinding
ProVAL Smoothness Assurance Model (SAM)Requires Experience
Only models in two dimensions which may cause impacts in other locations. Grinding wheels not necessarily on same profile as grinding head when large variations in transverse profile exist - May not be able to just correct a single wheel path
Must use the exact equipment modeled In some instances overestimates correction areas and
tends to be slower Corrects for ALR and not MRI
Start Distance (ft) Stop Distance (ft) Length (ft)
10.3 15.6 5.329.4 60.2 30.8
438.2 459.9 21.8512.1 521.0 8.9524.1 536.5 12.4568.1 582.8 14.8642.2 657.0 14.8688.8 698.3 9.4705.7 729.8 24.2
1953.3 1987.8 34.62004.9 2016.1 11.22024.3 2061.9 37.62064.7 2070.9 6.32071.1 2139.8 68.72168.3 2179.3 11.12201.7 2213.3 11.62217.8 2235.7 17.92236.3 2250.0 13.82260.3 2298.4 38.12341.3 2355.5 14.22364.0 2394.3 30.32417.8 2424.2 6.43375.7 3398.5 22.83407.0 3423.6 16.63427.5 3476.3 48.83510.5 3537.1 26.64347.8 4418.2 70.34452.4 4542.3 89.84573.3 4605.8 32.54881.1 4898.7 17.64899.1 4915.2 16.14917.4 4925.7 8.34957.3 4968.6 11.3
Proper locating with respect to lengths and locations of corrections is critical! Correction equipment operator’s transitions are critical!
Correct a bump. Create two more!
Corrections Take Experience and Skill
But Grinding or Cold Planing Corrections Can Only Do So Much
Can only go deeper or wider
Can’t fix a pavement or subgrade
WORKING CRACKS – Respond Dynamically to Vehicles, Including Inertial Profiler
Working – Not correctible by grinding
Non Working – Likely correctible by grinding
The Good News: While it may be unreasonable to expect to obtain
smoothness with the design strategy specified, there appears to be:
Better understanding of the issues involved by Contractors and the State
Better partnering to come to an equitable solution before construction begins
The Good News: There is effective dialog occurring in the Smoothness
Subtask Group – With a joint effort trying to resolve issues
Effective contractors have adapted and are raising the bar
The cry was – “It cannot be achieved” Now – “If the design strategy and existing roadway allows it, we
will get it” Many look forward to pay incentives that will likely be available
in the future (Late 2017 projects?)
The public is noticing
