bituminous compaction uniformity assessment using non … · 2020. 3. 17. · bituminous compaction...
TRANSCRIPT
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
Die
lectr
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
Lab
Mea
sure
d A
ir V
oids
(%)
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
Die
lect
ric
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