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Bituminous Compaction Uniformity Assessment Using Non · PDF file 2020. 3. 17. ·...

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  • Bituminous Compaction Uniformity

    Assessment Using Non-Destructive

    Testing GPR

    Dr. Shongtao Dai

    Office of Materials and Road Research,

    Mn/DOT

    Dr. Kyle Hoegh

    University of Minnesota

    Mn/DOT

    Office of Materials and Road Research

  • What is GPR?

     GPR is a noninvasive,

    nondestructive testing

    tool for mapping

    subsurface conditions

     Radio waves to detect

    objects and determine

    distance from the object

  •  Wave propagation in solids

    Each scan

  • GPR is an effective tool for thickness determination

    (similar to x-ray)

    GPR cannot identify material type or object

    (dielectric only)!

  •  Single frequency impulse GPR

     1 pair antenna: emits only one

    frequency

     2.0 GHz, 1.0 GHz, etc

     One transverse location in each

    pass

     Step Frequency GPR (3D-GPR)

    Multiple pair antenna

     11 pairs

    Frequency range: 50 MHz - 3.0 GHz

     Variable depth

     5ft footprint in each pass

    Traditional GPR and 3D GPR (Air Coupled)

  •  Ground-coupled: 2.5 GHz, 1.5 GHz, 400 MHz and

    100 MHz

     Walking speed

     Locate underground objects

    Approximate penetration depth:

    2.5 GHz: 1.0 ft

    1.5 GHz: 1.5 ft

    400 MHz: 10 ft

    100 MHz: 40 ft

     In general, the higher the frequency, the higher the

    resolution, but less penetration depth

  •  Pavement density has great effects on performance.  Lack of density --- localized failure

     1989 – “Effect of Compaction on Asphalt Concrete Performance” (Wash.DOT) Each 1% increase in air voids (over 7 percent)

    tends to produce ~10 percent loss in pavement life.

     Core used to determine density  At a particular location, not represent the entire

    pavement density.

     Need a way to obtain full coverage of the surface

     GPR is a potential good tool: Continuous profile

     Locate relative high or low density areas based on

    dielectric map

    Compaction Uniformity Mapping

  • a : dielectric constant of the material near the surface. a = [(1+A1/Am)/(1-(A1/Am)]²

  •  TH13 (June 27-28, 2012)  Overlay project

     Surveyed 300ft

    y = 0.0584x + 0.3046 R² = 0.9785

    5.5

    5.55

    5.6

    5.65

    5.7

    5.75

    5.8

    5.85

    5.9

    5.95

    90 92 94 96

    D ie

    le c tr

    ic

    Density (%)

  •  TH61 (White Bear, 2014)  4” mill and overlay

     Surveyed 600ft section on NB  2 times: test repeatability

    Surface Arrival Amplitude

    3D-GPR

  •  Dielectric Map  3” antenna spacing and 3” measurement spacing

    Trial 1

    Trail 2

  • TH494: South of Carlson Parkway

    1. 5ft coverage in the transverse direction in each Pass.

    2. 400 ft coverage in the longitudinal direction.

    3. Each pass over joint between two lanes.

    4. 3 passes total to ensure repeatability of data.

  • Core 2 Core 4 Core 6 Core 8

    Core 1 Core 3 Core 5

    Core 7

  • Lab Air Voids vs Dielectric of 3 Trials

    y = 151.46e-0.66x

    R² = 0.9436

    y = 136.82e-0.637x

    R² = 0.9176

    y = 177.63e-0.69x

    R² = 0.9512

    3.00

    4.00

    5.00

    6.00

    7.00

    8.00

    9.00

    10.00

    11.00

    4.00 4.50 5.00 5.50 6.00

    La b

    M ea

    su re

    d A

    ir V

    oi ds

    (% )

    GPR Measured Dielectric

    Lab Measured Air Voids vs. Dielectric

    Trial 1

    Trial 2

    Trial 3

    Expon. (Trial 1)

    Expon. (Trial 2)

    Expon. (Trial 3)

  • Air Void Map

  • The UofM SHRP2 Project: Rolling Density Meter (RDM)

  • Core 1: 4.5 in from joint on right lane

    TH25: moving from left lane to right lane

    (Air void:8.9%)

    L. Joint Core

  • 3

    3.5

    4

    4.5

    5

    5.5

    6

    0.0000 1.0000 2.0000 3.0000

    D ie

    le ct

    ri c

    Distance, ft.

    Static

    Transversal (003)

    Longitudinal (002)

    Core 4 Location

    Averaged Time Scan (001)

    LG_1

    LG_2

    Longitudinal Joint

    Core L. Joint

    (Air void:8.7%)

  • C01_6inAC1_Cl4

  • zcell14_114

  • Thank you

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