Concrete Pavement Thickness Agenda

Design & Slab Geometry

Review of Pavement Design History & Pavement Types
Distresses Related to Pavement/Slab Geometry
Tyler Speakmon, PhD Compare AASHTO 93 vs Pavement ME Designs
Infrastructure Solutions Engineer Incorporating Slab Geometry into Design Tools
CEMEX USA – Commercial Using Slab Geometry to Control Cracking Mechanisms
Cement Thickness
Joint Spacing
Widened Lanes
Additional Design Considerations and Jointing

In The Beginning… Early Concrete Pavement Details

The first concrete pavements/slabs

were:
≈ 6” thick… no real structural design
6’ to 8’ slabs
No crack control joints or dowels/steel

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Design Challenge | Solution CONCRETE PAVING SOLUTIONS
USING CONVENTIONAL CONCRETE
Shorter slabs w/ dowels & aggregate interlock to transfer loads
Vehicles Speeds Increased Jointed Plain Concrete Pavement (JPCP)

Loads Increased 10 – 16 ft.

or

People Noticed Joint Roughness & Wanted to Jointed Reinforced Concrete Pavement (JRCP)
Longer (than JPCP) jointed w/ dowels to transfer loads

Maximize Production to Minimize Cost | Minimize

Construction Joints 30 – 100 ft.

Continuously Reinforced Concrete Pavement (CRCP) Continuously reinforced to control crack width
Less of this and more of this!

2 – 6 ft.

JOINTED PLAIN CONCRETE Design also Requires an Understanding

PAVEMENTS (JPCP) – Key Design Items of How a Concrete Pavement Fails…
Surface smoothness Thickness design Structural Distress – Functional Distress –
the ability to carry traffic the ability to serve the user comfortably
Longitudinal joint
(incl location & spacing)
Cracking (dominant) Rough ride (IRI)
Transverse joint (mainly due to cracking and faulting)
(incl location & spacing)

Surface texture

Concrete mix design

Dowel bars Joint Faulting (dominant) Insufficient

Texture/friction
Joint Faulting (dominant)
(address through maintenance)
Tiebars
Subbase or base
Subgrade

Design requires understanding how design features impact cost and performance
(and getting the right balance for the application)

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Rigid Pavement Design Tools/Methods

AASHTOWare
Pavement ME
(previously known as
DARWin-ME and
MEPDG)

AASHTO 93

AASHTO 93 / WinPAS
(software as
ACPA WinPAS)
325 & 330

Equivalent Single Axle Loads TRAFFIC IS THE MAIN SOURCE OF

(ESALs) DAMAGE FOR PAVEMENTS
The Magnitude of Damage Depends on Vehicle Number, Type, and Load

ESAL = # of 18 kip (8,165 kg) equivalent single Equivalent Single Axle Loads (ESALs) Load Spectrum

axles needed to cause same “response” • Assumes traffic is only 18,000 lbs single axles
• Conversion of trucks to ESALs is empirical
• Consider traffic composed of axles w/
different weights

• Based on field test conducted 50 years ago • Required inputs:

Because pavement responses are different for • Traffic conditions significantly changed • Number of trucks

concrete and asphalt, ESALs are different for the between now and then • Axle load spectrum
• Function of roadway type

same exact traffic loading… ESAL ≠ traffic

ESALs
ESALs depends on thickness, among other things Single Tandem Tridem

Flexible ESALs generally about 1/3 less than rigid

ESALs for highway-type traffic; NEVER
COMPARE RIGID & FLEXIBLE ESALs

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1986-93 JPCP AASHTO 93 Equation WinPAS Makes it Easy!

Change in Serviceability
Overall
Standard Standard Deviation
Normal Deviate Thickness 
 PSI  
 Log  4.5  1.5  
Log ( ESAL)  Z R * so  7.35 * Log ( D  1)  0.06    
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 1.624 *10 
Traffic  1  ( D  1)8.46 
 
Modulus of
Drainage
Terminal Rupture
Coefficient
Serviceability  
 
S c * Cd * ( D  1.132)
' 0.75
 ( 4.22  0.32 * pt ) * Log  
  0.75 18.42  
 215.63 * J *  D  
  ( Ec / k ) 0.25  
Load Modulus of
Transfer
Modulus
of Elasticity Subgrade Reaction AASHTO 93 Slab Geometry involved => Thickness

Concrete Pavement Design

Methodologies
Outdated Current Design Tools
THE 40 YEAR DIVIDE

AASHTO 93 StreetPave PavementDesigner OptiPave Pavement ME

1962-1998 2005-2017 2018 - Present 2009 - 2018 2009-2018
10 inputs 12 inputs 12 inputs ≈ 50 inputs ≈ 1,000 inputs
“Performance” Crack & Fault Crack & Fault Crack, Fault, IRI Crack, Fault, IRI
Field Data FEA + Field Data FEA + Field Data FEA + Field Data FEA + Field Data

Increasing Complexity = More Accurate Models & More Optimization

Options

Industry Developed Methods

PavementDesigner.org

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PavementDesigner.org
Background

A free tool designed to simplify concrete pavement

design for:
Parking lots
Roadways (JPCP, RCC, CRCP, Overlays Unbonded & Bonded)
Industrial / Intermodal yards (Forklifts & Specialty Equipment)

Uses More Accurate Traffic Inputs MEPDG / DARWin-ME /

PD.org Slab Geometry => Thickness & Joint Spacing AASHTOWare Pavement ME

Pavement ME Design Sounds Easy Enough, Right?

Not “perfect” & not intended to be a “final” product

Complex and relatively costly
Primarily for high volume roadways

+ =
Mechanistic Empirical Pavement
Calculation Tie to Performance
of Responses Ground Prediction

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 Pavement ME’s Concrete Pavement Designs

New Pavement
MEPDG / DARWin-ME / AASHTOWare Pavement ME Jointed Plain Concrete Pavement (JPCP)
Concrete Pavement Design Continuously Reinforced Concrete Pavement (CRCP)
Options Overlay
Bonded PCC over JPCP or CRCP
Unbonded JPCP or CRCP over JPCP or CRCP
JPCP over AC
CRCP over AC
SJPCP over AC
Rehabilitation

Pavement ME Inputs… EXACT Traffic Inputs…

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Pavement ME Outputs… Pavement ME Performance Outputs

Jointed Plain Concrete JPCP – Characterizing Pavement

Pavement (JPCP) Structure

JPCP Design
Process
General Info and
Performance Criteria
Traffic Details
Climate
Characterizing
Pavement Structure
JPCP Design
Properties

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JPCP – Pavement Structure – PCC
JPCP – Design Properties
Materials

Let’s Break it Down

JPCP – Design Properties JPCP – Design Properties

SSA 0.85 (Default and semi-constant)

Doweled Joints Typically used if thickness > 8 in
Diameter Often depends on thickness
1 inch for 8 inches or less thickness
1.25 inches for 8 – 10 inches thickness
Let’s Break it Down 1.5 inches for >10 inches
Spacing 12 inches is most common

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JPCP – Design Properties JPCP – Design Properties

Curl/Warp Temp. -10oF (Good default)

Sealant Type Preformed or Other (none, liquid, silicone)
Erodibility Depends on soil conditions Tied Shoulder Project dependent
Base Friction Good defaults Widened Slab Project dependent
Joint Spacing Typical range = 12 – 20 ft

Pavement ME Slab Geometry Inputs include

Thickness, Joint Spacing, Lane Width

Summary of Unique JPCP Critical

SHORT JOINT SPACING IMPROVES
Inputs
JPCP PERFORMANCE
Performance Criteria
IRI, Cracking, Faulting PCC Strength Reduces Shrinkage Force Reduces Environmental Stress Improves Load Transfer
• Curling & warping is due to the • ~1/4 of slab length is cantilever • Shorter slabs have smaller
PCC Modulus differential drying and thermal
shrinkage at the slab surface
• Reducing unsupported length
reduces the bending stress
joint/crack opening
• Agg. Interlock stronger for tighter
Shorter slabs have less length,
Coef. of Thermal Exp. cracks
•

Thickness which means reduced curling • Reducing length reduces uplift and
improves smoothness • High load transfer results in less
stress in concrete
Joint Spacing Curing Method
Lane Width Base Erodibility Lifting Force
Cantilever = 1/4 L

Shoulder Type Mix Design (Cement type, Shrinkage Force

∆L

Dowel Design w/cm, etc.) Length 30 ft., cantilever = 7.5 ft

F/2 F/2 Cantilever = 1/4 L

∆L/2

BOLD => Inputs Related to Slab Geometry Length 12 to 15 ft., cantilever = 3 to 3.75 ft

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 SHORT JOINT SPACING REDUCES Engineering Solutions – Widened Slab Example
SLAB CRACKING
Joint Spacing vs. Slabs Cracked
100
19 million trucks (TTC 2 [30 million ESALs])
90 Wet-freeze climate
8- to 11-in JPCP; 6-in aggregate base
80
Percent slabs cracked

8-in slab 9-in slab

70
10-in slab
60
11-in slab
50

40

30
20

10

0
12 13 14 15 16 17 18 19 20
Joint spacing, ft
Maximum Joint spacing = 18 to 24 times thickness (15 ft max) (Rao, 2018)
Graph Developed by Tommy E. Nantung
INDOT Office of Research and Development

Engineering Solutions – Widened Slab Example Engineering Solutions – Widened Slab Example

Widening the slab reduces

longitudinal edge midpanel
stresses but this could
increase stresses in other
locations not considered in
Pavement ME

With 14 ft wide slab there is

a much higher risk of
longitudinal cracking due to
increased stresses at
interior transverse joint edge
locations
(Rao, 2018) (Rao, 2018)

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Highway Design Problem Additional Design Considerations
Related to Slab Geometry
Dowels
7,860 trucks (~20M • Edge Support Dowel Spacing
HMA Subbase = 1”
ESALs) •
Dowel Bar Diameter
• Cement Stb Subgrade = 6”
90% Reliability • K = 160 psi/in Edge Support
5% Slabs Cracked Tie Shoulders
Design:
6 lane facility •
• AASHTO 93 Jointing Layouts
= 11”
• PavementDesigner = 8.5”
R-Value = 20 • Pavement ME
MOR = 630 psi = 9” …CRCP Design Properties
E = 3,500,000 psi
PCC

Top 10 ME Design Most Sensitive Engineering Solutions - Faulting

1. Concrete Flexural Strength at 28-Days

Improve Mechanical LT
2. Concrete Thickness Increase Dowel Size
3. Surface Shortwave Absorptivity (SSA) Decrease Dowel Spacing
4. Joint Spacing Decrease Joint Spacing
5. Concrete Modulus of Elasticity at 28-Days
Increase Width of Lanes
6. Design Lane Width with a 14 ft (4.3 m) Widened Slab
7. Edge Support via Widened Slab Reduce Underlying Layer Erosion
8. Concrete Thermal Conductivity Increase Erodibility Index
9. Concrete Coefficient of Thermal Expansion (CTE) Decrease Joint Spacing
10. Concrete Unit Weight
Reduce Thickness
http://onlinepubs.trb.org/onlinepubs Only if Cracking is Passing
/nchrp/docs/NCHRP01-47_FR.pdf

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 Sensitivity of JPCP Faulting to Dowel Sensitivity of JPCP IRI Sensitivity to
Diameter Dowels
0.35 250
19 million trucks (TTC2 [30 million ESALs])
1" dowel 9.8-in slab; 15-ft joint spacing Non-doweled

0.3 6-in aggregate base

1.25" dowel 200
28-day MRpcc = 690 psi; Epcc = 4.4 Mpsi

0.25 1.375" dowel

1.25-in dowel
1.5" dowel 150
Faulting for 10 inch slab, ins

IRI, in/mi
0.2

0.15 1.375-in dowel

100

0.1
50
0.05

0 0
0 50 100 150 200 250 300 350 0 2 4 6 8 10 12 14 16 18 20 22 24 26

Age, months Pavement age, years

Sounds Easy Enough, Right? Continuously Reinforced Concrete Pavement (CRCP)

Resources: Check out crcpavement.org for more!

Rasmussen et al. (2011) Roesler & Hiller (2013) Roesler et al. (2016)

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 Pavement ME Allows Agencies To Develop And Use Local
CRCP Design Properties Related to Calibration Coefficients
Slab Geometry
Lane Width
Crack Spacing (Dependent on Steel Design & Base Friction)
Steel Design
% Steel
Bar Diameter
Bar Depth
Base Friction Coefficient
Shoulder Type You can save your local calibration coefficients as default or restore the national as default at one click

Local Calibration Result In ½-In Or Less Difference In

Local Calibration Examples Required Thickness Vs. National Calibration

Indiana DOT: Low Volume Application High Volume Application

Changed JPCP IRI J3 from 1.4929 to 1.05 because it was too sensitive to it 12 300

Pavement Thickness, mm
Ohio DOT:

Pavement Thickness, in
10 250

AASHTO 1993
Changed JPCP IRI calibrations 8 200

Calibration Coefficient Default (national) Ohio

6 150
PCC IRI J1 0.8203 0.82
PCC IRI J2 0.4417 3.7 4 100

NC
DE

IN

OK
AZ

MO

NY
IA

KS

OH

UT
VA

WY
LA

WA
PA
SC
PCC IRI J3 1.4929 1.711 AZ IA KS MO NY OK SC VA WY
PCC IRI J4 25.24 5.703
PCC IRI JPCP Standard Deviation 5.4 5.4
Pavement ME_LC Pavement ME_NC AASHTO 1993

However, using Pavement ME result in ~2-3 in thinner JPCPs when compared to the AASHTO 93 guide.
Many states at this point are working on or have
completed local calibrations. (Mu, 2017)

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Simpler ME Option: Design Tables
Conclusions:
• Slab Geometry is KEY to Optimizing Pavement
Designs
• Thickness is not the ONLY Slab Geometry that
Improves Performance
• Shorter Joint Spacings & Widened Lanes
Improve Pavement Performance
• Improvements in Design Tools, such as
Pavement ME, have allowed Designers to Utilize
all aspects of Slab Geometry to Yield more
Economical and Better Performing Concrete
Pavements

125 Yrs of Success and Performance Acknowledgements & References

Ferrebee, Eric 2020. AASHTOWare Pavement ME Design Workshop.
Presented to Arkansas DOT. 2-27-2020.
Mu, Feng 2017. Establish Pavement ME Design Inputs for New Jointed
Plain Concrete Pavements, Presentation to TAC Pavement ME User
Group Meeting, 4-21-2017.
Rao, Shreenath 2018. Pavement ME Design – 3M Edition – Myths,
Misuses, & Misconceptions, Presentation to 2018 CO/WY ACPA
Meeting, 3-22-2018.
Donahue, John & Jason Bloomberg 2018. AASHTO Pavement ME
Design Web Application JPCP Module, Presentation to MO/KS ACPA’s
38th Annual PCCP Conference, 2-20-2018.
It’s all about the thickness… right?

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Resources Resources

NCHRP 1-37 MEPDG Home: Some States with Pavement ME User Guides
http://onlinepubs.trb.org/onlinepubs/archive/mepdg/guide.htm Michigan:
Recorded Webinars: https://www.michigan.gov/documents/mdot/MDOT_Mechanistic_Empirical_Pavement_Design_
User_Guide_483676_7.pdf
https://www.fhwa.dot.gov/pavement/dgit/aashtoware.pdf Colorado: https://www.codot.gov/business/designsupport/matgeo/manuals/pdm/2017-
North American Usergroup Summary Page: m-e-pavement-design-manual/chapter-1.pdf

http://www.pooledfund.org/Details/Study/549 Indiana: http://www.in.gov/indot/design_manual/files/Ch304_2013.pdf

ME Design Help: http://www.me- Arizona:
https://apps.azdot.gov/ADOTLibrary/publications/project_reports/PDF/AZ606.pdf
design.com/MEDesign/data/HTML%20Help/US/index.html?design_inputs_1.htm
Virginia:
Application Library: http://apps.acpa.org/ http://www.virginiadot.org/VDOT/Business/asset_upload_file108_3638.pdf

Utah: https://www.udot.utah.gov/main/uconowner.gf?n=20339215312776663

Q&A / Discussion Thank you !

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