David  E.  Newcomb,  P.E.,  Ph.D.Texas  A&M  Transportation  Institute

Texas  A&M  University

The  Role  of  Perpetual  Pavementsin  Delivering  

Smooth,  Safe  and  Well-­‐Maintained  Roads

Australia  &  Texas:A  Case  for  A  Partnership!

Pavement  Engineer  Genome  Project

People

• Texas: 25,674,681 (2011)• Australia: 22,328,800 (2011)

• Texas has cowboys.• Australia has stockman.• Both love country music.

Wide  Open  Spaces

Animals  that  Hop

Only  Texas  has  the  Jackalope

Marsupials

Pavement  Basics• Layers  are  necessary  to  provide  economy  while  protecting  ‘weak’  materials

Pavement  Design:    Where  were  we?

• Using  1960s  performance  equations• 1950s  type  of  load• Thin  pavement  structures  (Max.  6”  HMA)• Meaning  of  structural  coefficients• Limited  reliability  analysis• Some  movement  to  M-­‐E

AASHO  Road  Test  Trucks

( )

( )

07.8log32.2

110944.0

5.12.4log

20.01log36.9log19.5

018 −+

++

⎥⎦

⎤⎢⎣

⎡−

Δ

+−++= RR M

SN

PSI

SNSZW

AASHTO  Design  Equation

Perpetual  Pavement  Design  Features

Max  Tensile  Strain

PavementFoundation

Rut  Resistant  Intermediate  Course75  – 100  mm  (3  – 4”)

Durable    Base100  – 250  mm  (4  – 10”)

38  – 75  mm  (1.5  -­‐ 3”)  SMA,  OGFC  or  Superpave} ZoneofHigh

Compression

Perpetual  Pavement  versusConventional  Design

0

5

10

15

20

25

0.1 1 10 100 1000

HMA  Thickness,  in.

Traffic,  ESAL

AASHTO  

PerRoad

Perpetual  Pavements• Resist  Structural  Distresses– Fatigue  Cracking– Rutting

• Withstand  Climate  and  Traffic– Design  for  Subgrade  Modulus– Use  Strong  Foundation– Mix  Design– Materials  Selection

Perpetual  Pavement  Advantage• Efficient  Design  – No  Overdesign• Avoid  Reconstruction• Reduce  Rehabilitation• Reduce  Life  Cycle  Cost• Reduce  Energy  Consumption• Reduce  Materials  Use

DBM

DBM50HDM

Design  life  (msa)

Thickness  of  asphalt  layers(mm)

500

400

300

200

100

0

DESIGN  CURVES  FORASPHALT  PAVEMENTS

Thickness  of  bituminous  layer  (mm)

Rate  ofrutting

(mm/msa)

0 100 200 300 4000.1

1

10

100

1000

RATE  OF  RUTTING  vsBOUND  LAYER  THICKNESS

New  Jersey  I-­‐287Surface  Cracking

Design  Applications• High  Volume  Pavements– MEPDG– PerRoad– TTI

• Low  and  Medium  Volume  Pavements– PerRoad

• High  Modulus  Bases• Pavement  Rehab  – SHRP  2  – Project  R23– Using  Existing  Pavement  in  Place  and  Achieving  Long  Life– Rubblization– Overlays

Performance

• Perpetual  Pavement  Awards• European  Studies• Oregon  and  Washington  Studies• New  Jersey• Connecticut• Kansas– Review  of  interstate  performance– Test  sections

Asphalt  vs.  PCC  Life

0

200

400

600

800

1000

0  -­  10 11  -­  20 21  -­  30 31  -­  40 41  -­  50 51    -­  60 61  or  More

Age  (Years)

Lane  Miles

HMA  (Lane  Miles)PCCP  (Lane  Miles)WSDOT  

Interstate  Ages

Smoothness

0

200

400

600

800

1000

1200

0.0  -­  0.5 0.5  -­  1.0 1.0  -­  1.5 1.5  -­  2.0 2.0  -­  2.5 2.5  -­  3.0 3.0  -­  3.5 3.5  -­  4.0 4.0  -­  4.5 4.5  -­  5.0 5.0  orMore

IRI  (m/km)

Lane  Miles

HMA  (Lane  Miles)PCCP  (Lane  Miles)

WSDOT  Interstate  – Roughness  (2004)

RUBBLIZATION WITH  PERPETUAL  PAVEMENT  OVERLAY  

VERSUS  REMOVE/REPLACE  PCC

First  Cost  Comparisons

• One  Lane-­‐Mile  (7040  SY)• Case  1:  Rubblization with  Perpetual  Pavement• Case  2:  Remove  PCC  and  Replace  with  PCC

Case  1

• Perpetual  Pavement  with  Rubblization– Rubblize28  cm  PCC– Overlay  with  20  cm  HMA

• Initial  Cost:• 2013  Bid  Tabs

– CO  Rubbl.  ~  $5.00– CO  SMA  ~  $85.00– CO  HMA  ~  $75.00– TX  HMA  ~  $70.00– WA  HMA  ~  $85.00

Item Unit  Cost

Edge  Drains

5.00/ft16.40/m

Rubblize 5.50/yd2

6.57/m2

HMA  Overlay

80.00/ton88.00/t

Case  2

• Remove/Replace  PCC  – Remove  PCC– Replace  with  11”  PCC

• Initial  Cost:– 2013  Bid  Tabs  PCC

• CO  ~  $34.00• WA  ~  $47.00

Item Unit  Cost

Remove  PCC 25.00/yd2

29.90/m2

PCC  Placement

41.00/yd2

49.04/m2

Initial  Cost  Comparison

0

100000

200000

300000

400000

500000

Rubblize  and  Overlay

Remove/Replace  PCC

Cost,  $/lan

e-­‐mile

Δ =  32%

General  Experience

• First  Cost:  Rubblization ~  32%  less  than  remove/replace

• Speed  of  Construction:  days  vs.  weeks• Impact  of  User  Costs?

Work  Zone  Assumptions

• 1  mile  long• 4  lanes  • One  lane  open  each  direction  during  work• 40,000  ADT

Case  1• Rubblization:  One  lane-­‐mile/day  production• Paving:  2  lane-­‐miles/day– Sequence

• 3”  bottom  lift• 3”  2nd lift• 2”  3rd lift

– 24  hour  closure  until  2nd asphalt  lift– 12  hour  closure  for  3rd

Case  2• Remove/Replace  PCC– Removal:  2000  SY/day    ~  2  days/lane  – 24  hr/day– Trim  Base  and  Set  Dowels  – 12  hr– Paving:  0.75  mile/day  – 11  hr– Curing:  3  days  – 24  hr/day  

User  Costs

0

10000

20000

30000

40000

50000

60000

70000

Rubblize  and  Overlay Remove/Replace  PCC

Cost,  $/lan

e-­‐mile

Δ =  58%

Life  Cycle  Costs• Asphalt– Initial  Construction– Overlay  Every  15  years

• Concrete– Initial  Construction– Grind  at  Year  15– Overlay  at  25  years– Overlay  at  35  years

Life  Cycle  Costs

0

100000

200000

300000

400000

500000

600000

700000

Rubblize  and  Overlay Remove/Replace  PCC

Cost,  $/lan

e-­‐mile

Δ =  22%

Summary• Perpetual  Pavement  design  is  improving– More  efficient  pavements– More  cost-­‐effective

• Construction  issues  need  to  be  addressed• Perpetual  Pavement  is  Less  Expensive– Initial  Cost– User  Cost  – Life  Cycle  Cost

Tools  for  Performing  Perpetual  Pavement  Design  and  LCCA

• LCCA  Software  – Asphalt  Pavement  Alliance– Follows  FHWA  Guidance– LCCA  Software  – Full  probabilistic  analysis– LCCA  Express  – Direct  comparison  of  two  options  –deterministic.

• Design  Software– PerRoad – Full  Perpetual  Pavement  Design– PerRoadXpress – Better  for  lower  volume  roads,  streets  and  parking  lots

• www.AsphaltRoads.org