What’s Known and What’s New - publish.illinois.edupublish.illinois.edu/bituminous/files/2016/05/Murphy-Compaction...Report 202 (1984) TRB declared that ... Reed tachometer; vibrations

Timothy R. Murphy, P.E.President

Whats Known and Whats New

Transportation Research Boards Report 202 (1984)

TRB declared that "asphalt, more than any other single product, sustains the nation's highway system and facilitates the flow of commerce."

Mr. Allan WoodUS Army, 82nd AirborneParachuted into Holland 9/17/1944Operation Market Garden &The Battle of the BulgePurple HeartBronze Star for combat valorE-mail: [email protected]'

Trucking Compaction

PavingHMA Facility

Balancing Production

Permeability reduction,

Public satisfaction,

Performance enhancement.

Density,

Smoothness,

Strength.

Why do we care about compaction?

Improve Mechanical Stability Improve Resistance to Permanent

Deformation

Reduce Moisture/Air Penetration Improve Fatigue Resistance Reduce Low-Temperature Cracking Potential

Importance of VMA

Permeability and rutting

Reference Density ComparisonIn-PlaceAir Voids

0

1

2

3

4

5

6

7

8

991

92

93

94

95

96

97

98

99

100

% of MaximumTheoretical Density

100

99

98

97

96

95

% ofLaboratory

Density

100

99

% ofControl Strip

Density

For 4.0% VoidsMix Design

Mat during Compaction

Courtesy of Caterpillar Paving Products

Types of rollers

1. Vibratory (aka Breakdown)

2. Pneumatic (aka Rubber tire)

3. Static Steel Wheel (aka Finish)

Den

sity

Incr

easi

ngHigh

Low

DensityPassing

1 2 43 5 6

Roller Passes

Marshall Mixes

Superpave Mixes

7 8

Vibratory roller

Method of expressing a vibratory rollers impact force on the asphalt pavement.

Increase with lift thickness. Vary with mix characteristics.

Unit Total Applied Force (UTAF)

UTAF (lb. / in.)

1 Surface Course 290 - 370

1 Binder Course 330 - 420

3 Base Course 400 - 500

4 plus Base Course 440 - 600

Desirable UTAF Ranges

Amplitude

DIRECTION OF TRAVEL

Impact Spacing

High FrequencyLow Frequency

Reed tachometer; vibrations per minute (vpm)

35(x100)

Typical Data for Vibratory Tandem Rollers

Vibratory Steel Tandem

(ton)

Oper.Wt.(lb.)

DrumDiam.(ft.)

Drum Width

(ft.)

Static Drum(pli)

Dynamic Drum(pli)

VPMNom. Amp. (in.)

6.0-8.0 14,700 3.6 4.6 130 260 2,900 0.0259.5-11.0 20,500 3.9 5.6 158 384 2,600 0.03> 13.0 30,000 4.9 6.9 186 423 2,400 0.03

Lack of smoothness

Do not vibrate thin lifts of Asphalt

Roller vs. paving widths

Roller in training

Skirted pneumatic roller

Tire inflation pressure vs. ground contact pressure


Inflation Pressure and Ground Contact Pressure at Various Wheel Loads and Ply Ratings

Ply Rating

Wheel Loadlb

Tire Pressure

psi

Contact Areain2

Ground Contact Pressure

psi

* 14 1,250 130 16 7814 2,800 130 30 92* 14 2,300 35 41 5614 2,300 130 26 88* 10 2,800 90 38 7314 2,800 130 30 92

Finish rolling removes marks and gets a touch more density with pounds per lineal inch (PLI) ~ 280

Ballasting finish roller to get PLI > 300

Properties of the Materials Environmental Variables Laydown Site Conditions

Factors Affecting Compaction

Can mix type and base support cause compaction difficulties?

Compaction compromised

Forces must be equal and opposite Sub-grade, Sub-base, Existing pavement structure.

How do we ensure adequate compaction?

Sub-grade

Sub-base

Sub-base density checks

Hot Mix Asphalt, Concrete, Oil & chip.

Existing pavement structure

Is it

con

cret

e?

Yes;

Rubbilize

See Process

See Photos

No;

No ProblemOverlay

Engineering Flowchart for Concrete Pavement

Process

Rubblization Photos

Courteous Contractor

Placement Equipment

Augers

SensorsSlat feeders

Hopper

Screed Tractor


Pre-Pave Meeting

Watch out for moisture

How worn flights affect temperatures

TEMPERATURES ACROSS THE INTAKE BREECHING SHOULD BE CONSTANT.

Evaluation of Asphalt Absorption by Mineral Aggregate AAPT 1991, p. 207-229.

Asphalt Absorption vs . Aging

0 1 2 3 4 5 6 7 8 Time, hr.

Abso

rptio

n, %

Wt.

Aggr

egat

e In

crea

sing

PG58-28

PG64-22 Curves vary from aggregate to aggregate.

Absorption, % Wt. Aggregate

Increasing

Evaluation of Asphalt Absorption by Mineral Aggregate

AAPT 1991, p. 207-229.

Curves vary from aggregate to aggregate.

PG64-22

PG58-28

Time, hr.

8

7

6

5

4

3

2

1

0

. Aging

vs

Asphalt Absorption

Silo & Truck loading: Recognize the evil spirit

Night paving

Truck Tarping

Side Insulation

262.0

164.8

*>270.0F

*

Pre-Pave Adjustments

Screed Unit

Courtesy of Blaw-Knox Ingersoll Rand Paving Products

Screed temperature

Lift Thickness

General rule of thumb is 3-times the maximum particle size; compacted lift thickness.

Variable thickness yields variable density.

Low Density = 88.9High Density = 94.4Avg. Density = 91.8Std Deviation= 1.7

Straight Longitudinal Lines

Construction

Longitudinal Joints Start with a Straight Line

Opportunity

Not so excellent joint construction

Wheres the Raker?

Compaction problems along the longitudinal joint

We are headed to hanging out at the joint

Longitudinal joint solution

Echelon Paving, Part II

Paver Operation

GOOD!!!

BAD!!!

End of truck load / dumping hopper wings [from afar]

151.0

212.2

163.1

228.1

*>237.6F

*

Ingenuity

Longitudinal Segregation & Cracking

Auger hold point

Bearing / hanger

Tools of the trade

Special Thanks to the

TxDOT Mr. Dale Rand, P.E.

Why is Thermal Segregation Important?

Cold spots typically become low density Density is the primary contributor to

performance

Contractor and agency risk are impactedAcceptance and pay schedules are based on densitySegregated locations may deteriorate prematurely

Research conducted by University of Connecticut, Connecticut Advanced Pavement Laboratory

Example of a Density Profile

End of truckload segregation

Fatigue Life Substantially Reduced

Source: NCAT (2000)

Sampling Distributions of Segregated and Non-Segregated HMA

Common Methods of Measuring Thermal Segregation

Infrared Thermometers less than $200 Infrared Cameras less than $5K Pave-IR System less than $30K

Test Method Tex-244-F Handheld IR thermometer Thermal camera Pave-IR

End dump operation shows cyclic paving speed decrease with cyclic thermal segregation

Background, Use, and Advanced Techniques

Dale Rand (TxDOT)

Richard Izzo (TxDOT)

Stephen Sebesta (TTI)

PAVE IR Conclusions

TxDOT is implementing better specifications & better techniques to address the problem

Excellent Passive Inspection device that allows end result versus method specifications

Contractors to see what they are doing and improve their operations

Contractors can focus on causes & cures

What Gets Measured Gets Done

Questions?

[email protected]

Compaction of AsphaltTransportation Research Boards Report 202 (1984)Balancing ProductionWhy do we care about compaction?Hot Mix Asphalt (HMA)Importance of VMAPermeability and ruttingReference Density ComparisonMat during CompactionTypes of rollersSlide Number 11Vibratory rollerUnit Total Applied Force (UTAF)Unit Total Applied Force (UTAF)Desirable UTAF RangesSlide Number 16Slide Number 17Reed tachometer; vibrations per minute (vpm)Typical Data for Vibratory Tandem RollersLack of smoothnessDo not vibrate thin lifts of AsphaltDo not vibrate thin lifts of AsphaltRoller vs. paving widthsRoller in trainingSkirted pneumatic rollerTire inflation pressure vs. ground contact pressureInflation Pressure and Ground Contact Pressure at Various Wheel Loads and Ply RatingsFinish rolling removes marks and gets a touch more density with pounds per lineal inch (PLI) ~ 280Ballasting finish roller to get PLI > 300Factors Affecting CompactionCan mix type and base support cause compaction difficulties?Compaction compromisedHow do we ensure adequate compaction?Sub-gradeSub-baseSub-base density checksExisting pavement structureEngineering Flowchart for Concrete PavementSlide Number 39Slide Number 40Slide Number 41Courteous ContractorPlacement EquipmentSlide Number 44Pre-Pave MeetingWatch out for moistureHow worn flights affect temperaturesSlide Number 48Slide Number 49Silo & Truck loading: Recognize the evil spiritSlide Number 51Night pavingTruck TarpingSide InsulationInfrared Photo of End DumpPre-Pave AdjustmentsScreed UnitScreed temperatureLift ThicknessStraight Longitudinal LinesSlide Number 61OpportunityNot so excellent joint constructionWheres the Raker?Compaction problems along the longitudinal jointWe are headed to hanging out at the jointLongitudinal joint solutionEchelon Paving, Part IISlide Number 69End of truck load / dumping hopper wings [from afar]Infrared Photo(End Dump Mix Behind Paver)IngenuitySlide Number 73Slide Number 74Slide Number 75Auger hold pointBearing / hangerTools of the tradePAVE - IRWhy is Thermal Segregation Important?Slide Number 81End of truckload segregationFatigue Life Substantially ReducedSampling Distributions of Segregated and Non-Segregated HMACommon Methods of Measuring Thermal SegregationMeasuring Thermal SegregationEnd dump operation shows cyclic paving speed decrease with cyclic thermal segregationSlide Number 88PAVE IR ConclusionsPAVE-IR COMPONENTSQuestions?

Documents

What’s Known and What’s New - publish.illinois.edupublish.illinois.edu/bituminous/files/2016/05/Murphy-Compaction...Report 202 (1984) TRB declared that ... Reed tachometer; vibrations