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  • Concrete Pavement Overlay Design Jeffery Roesler, Ph.D., P.E. Professor Department of Civil & Env. Eng. University of Illinois Urbana-Champaign

    25 June 2015 ISCP Concrete Pavement Seminar IDOT District 1 (Schaumburg, IL)

  • Concrete Overlay Overview  Overlay Design Objectives  Overlay Design Guides  Inputs & critical variables  Bonded Concrete Overlays

     Concrete-Asphalt

     Unbonded Concrete Overlays  Whitetopping & Composites

     Performance of Illinois O/L  References for O/L design  Summary of Overlay Design

  • Concrete Overlay Design: Objectives  Achieve desired concrete pavement overlay

    service life given:  Existing pavement condition  Expected traffic  Layer and material properties  Interface condition  Slab geometry  Climatic conditions

    SCinitial SCOverlay

    SCeffective SCfuture traffic

    Load Applications

  • - 76

  • Guide on Existing Overlay Design Methods

     Not a design procedure  Background on

    recommended overlay design methods  18 pages

     Detailed design examples  35 pages

     StreetPave12 released after this guide

    http://www.cptechcenter.org/technical-library/documents/Overlays_Design_Guide_508.pdf

  • How to start design of concrete O/L?  Roadway site evaluation  Existing pavement structure  New pavement performance objectives  Select candidate Overlay Options  Collect input data & choose design features

     Support layers, Slab size, etc.

     Use appropriate overlay design methods  Optimize design  Write construction specs to reflect design objectives

  • Concrete Overlays: General Types

    Whitetopping (unbonded) Bonded Concrete Overlay Asphalt (BCOA)

    Bonded Concrete to Concrete Unbonded Concrete w/ Separation Layer

  • Concrete Overlay Guide, Third Edition Contents

     Overview of Overlays  Overlay types and uses  Evaluations & Selections  Six Overlay Summaries  Design Section  Misc. Design Details  Overlay Materials Section  Work Zones under Traffic  Overlay Construction  Accelerated Construction  Specification

    Considerations  Repairs of Overlays

    http://www.cptechcenter.org/technical-library/documents/Overlays_3rd_edition.pdf

  • Concrete Overlays Categories

    Concrete Overlays

    Bonded Concrete Resurfacing of Concrete Pavements

    Bonded Concrete Resurfacing of Asphalt Pavements

    Bonded Concrete Resurfacing of Composite Pavements

    Bonded Overlay Group

    Unbonded Concrete Resurfacing of Concrete Pavements

    Unbonded Concrete Resurfacing of Asphalt Pavements

    Unbonded Concrete Resurfacing of Composite Pavements

    Unbonded Overlay Group

    Thinner Thicker

    Bond is integral to design Old pavement is base layer

  • Thinner Concrete Pavement Options

    Bonded Concrete Resurfacing of Asphalt Pavements

    Bonded Concrete Resurfacing of Composite Pavements

    Bonded Overlay Systems

    Unbonded Concrete Resurfacing of Concrete Pavements

    Unbonded Concrete Resurfacing of Asphalt Pavements

    Thinner Concrete Pavement or Short Slabs

    Unbonded Systems

    ACPA BCOA or BCOA ME h=3 to 6 in. L=4 to 6 ft

    Thin Concrete

    Inlay - Preservation

    h=2 to 3.5 inch L=4 to 6 ft Emerging

    Colorado Method 6in. x 6ft x 6ft

    Opti-Pave h=2.5 to 9 in. L=4 to 9 ft

  • Which Overlay Design Method(s)? Concrete Overlay Type Design Methods Unbonded on Asphalt, Composite, or Concrete

    AASHTO ME, ACPA StreetPave 12, AASHTO 93, OptiPave 2.0

    Bonded on Asphalt or Composite

    ACPA BCOA, ACPA StreetPave 12, BCOA ME, CO 6x6x6, IDOT Chpt 53

    Bonded on Concrete AASHTO ME, ACPA StreetPave 12, AASHTO 93

  • • Slab thickness • Concrete Strength, CTE, Modulus, fibers (?) • Concrete-Asphalt Interface • Support layers (surface, base/subbase, soil) • Joint Spacing • Edge Support • Load Transfer • Subgrade Support • Traffic & Design Life • Climate

    What are main Concrete Overlays Design Inputs?

    Hamilton County, IL

  •  Pre-overlay Repair & Reflective Crack Control  Sub-drainage  Structural vs Functional Overlays  Recycling Existing Pavement (PCC & AC)  Existing PCC Slab Durability  PCC Overlay Reinforcement  PCC Overlays Bonding / Separation Layers  Overlay Design Reliability Level  Pavement Widening  Traffic Disruptions and User Delay Costs

    Other Important Considerations in Overlay Design

  • BCOA vs. “Whitetopping”  Whitetopping (h > 6 in.)

     More conventional slab sizes (6ft to 15ft)

     30+ years experience

     Ignores interface bond (unbonded)

     Bonded Concrete Overlay Asphalt (h ≤ 6 in.)  20+ years experience (1991)

     Smaller slab sizes (≤ 6ft)

     Concrete/AC bond is essential

     Ultra-Thin Whitetopping (UTW)

  • Composite Behavior Mechanics

    Unbonded “Whitetopping”

    Neutral Axis PCC

    Bit.

    Bonded Bonded Concrete Overlay Asphalt

    PCC

    Bit.

    Riley

  • Concrete Overlay Solutions: Rehabilitation and Maintenance

  • Site Visit: Existing Pavement Condition

  • Why use smaller slab sizes?

    1.2m 1.2m1.2m >2m

    •Interface bond assumption (BCOA) -Reduce de-bonding of concrete and asphalt at early ages

    •Short slab sizes reduce bending and curling stresses

  • Thickness Design for Concrete Overlays  Highways/Roads  AASHTO Pavement ME (2011) or MEPDG  StreetPave 12 (ACPA)  ACPA (Whitetopping/UTW) – 1998

     Illinois DOT (2009) – new fatigue eqn. & fibers  Chapter 53-4.08

     BCOA Calculator (2012) – add climate database

     BCOA ME (2012) – Univ. of Pittsburg  AASHTO (1993)

     Airports:  Federal Aviation Administration (FAARFIELD)

  • AASHTO Pavement ME or formerly known as MEPDG

  • AASHTO Pavement ME - INPUTS!

  • Many OUTPUTS to Synthesize

  • Bonded Concrete Overlay Options

     Thinner overlays (3 to 6 in)  Constructed over concrete,

    asphalt, and composite sections.

     Existing pavement condition fair to good

     Interface Bond is Critical!

    Bonded Concrete

    Resurfacing of

    Concrete Pavements

    Bonded Concrete

    Resurfacing of

    Asphalt Pavements

    Bonded Concrete

    Resurfacing of

    Composite Pavements

    Bonded Overlay Options

  • Bonded Concrete Overlay of Asphalt AASHTO 1993  Not applicable AASHTO Pavement ME (2011)  Thickness  6 in.  Slab length  10ft ACPA (2012);IDOT (2009);Pitt BCOA ME (2013) Ultra-Thin Whitetopping  Thickness  6 in.  Slab length  6ft

    Unbonded Concrete Overlay of HMA

    http://apps.acpa.org/apps/bcoa.aspx

  • HMA

    PCC

    Base

    40kN 40kN

    EAC, AC

    EPCC t

    AC

    Subgrade k-value

    Bonded

    hPCC

    hAC

    BCOA Critical Locations (Concrete and AC Layers)

    t

  • Fibers  Structural vs. non-structural (plastic shrinkage)

    Structural Macro-Fibers

    Micro-Fibers (non-structural)

    0 1 2 3 4 5

    0 10 20 30 40 CMOD (mm)

    Lo ad

    (k N

    )

  • IDOT Concrete Thickness Calculation

    Variable

    Design Traffic Factor (BDE Manual, Figure 54-4C) TF 2.50

    Modulus of Rupture (3-point bending, 14-day average) MOR 750 psi MOR FRC Residual Strength Ratio 20%

    Remaining Thickness of Asphalt h ac 3.0 in. Joint Spacing L 72 in. L

    Elastic Modulus of Concrete E c 3,600,000 psi E c Coefficient of Thermal Expansion CTE 5.50E-06 in./in./°F CTE

    Elastic Modulus of Asphalt E AC 350,000 psi

    Modulus of Subgrade Reaction k 100 pci

    k

    Thickness of Concrete h c 5.48 in. Solved

    Note 1: The design MOR is the mean design strength, not the minimum 550 psi flexural strength (center-point loading) specified for opening to traffic. Also note that as MOR increases the risk of debonding increases and the effectiveness of synthetic fibers decreases.

    PCC Inlay / Overlay Design Sheet, Required Thickness of PCC

    5.50 x 10-6 in./in./°F

    E AC

    100,000 psi (poor) 350,000 psi (moderate)

    3,600,000 psi

    0% (w/o fiber reinforcement) 20% (w/ fiber reinforcement)

    600,000 psi (good)

    100 pci

    Default Inputs Default Value

    750 psi (Note 1)

    48 in. or 72 in.

    150 150R

    Compute Concrete Thickness

    Help

    150 150R

    http://www.dot.state.il.us/desenv/pdp.html

  • IDOT Chapter 53-4.08 Tables

  • Asphalt Modulus (Eac)

    0

    1

    2

    3

    4

    5

    6

    1E+04 1E+05 1E+06 1E+07

    ESALs

    Co nc

    re te

    T hi

    ck ne

    ss h

    c (in

    )

    Eac = 100,000psi Eac = 350,000psi Eac = 600,000psi

    k = 100 pci

    MOR = 650 psi

    R150 = 0%

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