ride quality

Ride QualitySmooth Sailing or Fasten

Your Seat Belts?

307-213-0223 [email protected] © Mike Robinson, PE307-213-0223 [email protected] © Mike Robinson, PE

California Asphalt Pavement Association – Ontario – April 20, 2016

Photo courtesy of Tom Massaro

The Case for Smoothness

• Lower fuel consumption

• Less pollution

• Less vehicle wear and tear and damage

• Less damage to freight


• Less damage to freight

• Less pavement damage from vehicle dynamics

• Happier traveling public

• More money for roads!!!

Why Now?

• Always have had some ride quality

requirements

– Buyer’s impression

– Straightedge


– Straightedge

– Profilograph

International Roughness Index

• Improved technology makes it possible

• FHWA initiative

– Increase pavement life

– Decrease user costs


– Decrease user costs

– Improve public perception

The Key Differences

• Measuring actual profile rather than looking

for deviations over 12’ or 25’

• Simulating profile’s effect on vehicle

response


response

– Unsprung components

– Suspension / vehicle / occupant response

About 7’ About 50’


The “Wheel Hop” End We Understand

• Shorter wavelength roughness is easy

– Rotomill can take it out

– Paver can take it out

– Straightedge can find it (usually)


– Straightedge can find it (usually)

– Profilograph can find it

– Diamond grinder can find it

Longer Wavelength / Dynamics

• Longer than the tools we use

• Can’t “see” them

– Have to rely on ProVAL software

• Simulated vehicle dynamics affect the result


• Simulated vehicle dynamics affect the result

What It Boils Down To:The time, effort, and money spent to achieve a

given level of final ride quality depends on:

– The pre-construction ride quality for overlays

– The number and types of opportunities for


– The number and types of opportunities for improvement

– The practices employed at each opportunity

It is no longer just a matter of grinding bumps after paving.

How Important is This Change?

• Disputes & Claims in the millions

• Claim amount exceeding the original contract

amount

• Grinding costs equivalent to adding an


• Grinding costs equivalent to adding an

additional 0.10’ overlay over the entire

project

How Can You Succeed?

• Be aware of every opportunity for ride

quality improvement

• Know best practices

• Implement best practices


• Implement best practices

• Monitor your work – know what you can and

cannot accomplish

• Be concerned and willing to learn

Opportunities for Improvement

• Corrections applied to existing surface

• Cold milling

• Cold-In-Place Recycling

• Intermediate lifts


• Intermediate lifts

• Corrections applied to intermediate lifts

• Final lift

• Corrections applied to final lift

Leveling Course

307-213-0223 [email protected] © Mike Robinson, PE307-213-0223 [email protected] Mike Robinson, PE


Pre-paving Grind


Leveling Course Followed by Grinding

More than one removal option


What you pave on matters


Best Practices - General

• CONSISTENCY IS KEY

• Maintain constant speed – DO NOT STOP

– Milling

– CIR


– CIR

– Paving


• Balance operation

– Mix production

– Haul

• To the paver, from the coldmill


– Paver / Coldmill speed

– Compaction of mix

• Hot

• Warm

• Cold

Best Practices -

General• Use as long an averaging reference as

possible

– Sensors at each end of the cold mill

– Ski


– Ski

– Mat referencer

– Long-wheelbase grinder

• Control cross-slope as well as profile


• Reference as smooth a surface as possible

– Existing surface

– Previously-ground or placed lane


Best Practices – Milling

• Consistent maintenance


• Consistent maintenance

– Blocks and teeth

– Referencing equipment

– Machine in general

• May want fine or micro-milling, especially for

single, thin overlays

Best Practices – Leveling Course

• Choose an appropriate mix

• Make sure you have adequate time to

compact

– Thin lifts cool very quickly – Multicool


– Thin lifts cool very quickly – Multicool

recommended

• Use pneumatic rollers

– Steel drums will bridge

Best Practices – CIR

• Verify existing conditions for consistency

• Have a choice to make:

– Constant depth

• More consistent material


• More consistent material

• Little to no ride quality improvement

– Variable depth – profile correction

• Less consistent material

• Can improve ride quality significantly

Photo courtesy of Darren Coughlin

Best Practices – CIR

• You can grind bumps on CIR

– Make sure recompaction is good before grinding

– May need to grind in cooler conditions (i.e.

nights or mornings)


nights or mornings)

– Focus on high spots, not dips

– Choose tool and timing carefully

• Some have reported raveling of ground surface when

exposed to traffic for extended periods

• Remember – CIR is not HMA


Best Practices –

Paving

• Choose an appropriate mix

• Control mix properties

– Gradation

– Binder content

– Temperature

– Segregation


Best Practices – Paving

• Balance production / haul / placement /

compaction

• Monitor time available to compact

– Multicool

– May need to adjust for changing conditions


– May need to adjust for changing conditions



• Minimize contact with the paver

– Windrow paving

– Material transfer device / vehicle

Best Practices – Paving• Avoid thermal and mechanical segregation in

the hopper

– Either fold the wings after every load, or never fold

them

– Do not run the hopper below half full


– Do not run the hopper below half full


• If end dumping

– Do not back into the paver – let the paver pick up

the truck

– “Break” the load before releasing the end gate


– “Break” the load before releasing the end gate

– Flood the hopper

Best Practices –

Paving

Do not allow

material to

overflow


overflow



• Set flow gates to allow for balanced flow and

steady flight chain operation

– If paver is not centered on pass, adjust

accordingly


• Use auger and tunnel extensions as necessary

• Use material management / anti-segregation

baffles / chain curtains / etc.




Maintain a constant (and proper) head of

material ahead of the screed


• Create as straight a joint as possible

– Stringline and guide

– If you cut the longitudinal joint back, cut it in a

straight line


straight line

• Pave in constant widths as much as possible

• If you have to adjust widths, do it slowly and

adjust material flow

Best Practices –

Paving


• Minimize raking

• Do not walk on the mat

Best Practices –

Paving


• Do not park the rollers on the mat

• Reverse roller direction at an angle

• Control roller speed, particularly on turns



• Use a straightedge on construction joints

• Leave enough manpower and material to

build the joint

Reasonable Expectations

• Ride quality after any given opportunity for

improvement

– Depends on the existing ride quality

– Will generally be no better than about 60% of


– Will generally be no better than about 60% of

pre-operation ride quality

• You results may vary – you need to know

what you can accomplish.



• Leveling course

– Generally less improvement than overlay

– Can be improved with stringline / cuts & fills

• Remember differential compaction

– You can grind or mill leveling courses


• Cold-In-Place recycling

– MRI of 80 to 90 inches per mile is possible

• Assuming good paving practices

• Assuming good recompaction


• Assuming good recompaction




• Cold milling

– About 60% of pre-milling ride quality is possible

– Requires grade control and good reference

– Requires grinding for ride, not production

– May require fine or micro texture



• Bump grinding

– Difficult to fix low spots

– Deep grinds are slow, create more disposal, and

may run afoul of specifications

– Longer wheelbase can help


• Paving

– About 60% of pre-paving ride quality is possible

– Can be considerably less if pre-paving ride quality is

high


high

– Depends on paving practices used

Reasonable Improvement from FHWA FP-03:

– Single lift – 12-26 percent improvement

– Multiple lifts – 34-43 percent improvement

New construction should yield 60-65 in/mi final MRI


• ProVAL Smoothness Assurance Module

– 2D simulation of a 3D situation

– Assumes precise depth control of grinder

– Grinder must be accurately input

• Results for an 18’ wheelbase will not match the


• Results for an 18’ wheelbase will not match the simulation for a 25’ wheelbase grinder

– Does not account for grinder wear, ability to transition, tendency to ride out of cut, etc.

– Accurate locations of grinds are essential – use GPS, not just the DMI

– Dependant on who runs the grinding simulation

So…


Be careful

So…


Pay attention to details

So…

• Look at what you are paving on

• Look at every opportunity to improve ride

quality


quality

• Use best practices

• Know what you can and cannot accomplish

ride quality

Engineering