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Materials Sci ence & Technolog y
Stiffness Comparisons of Mastics Asphalt in Different Test Modes
2nd Workshop on 4PB at Guimarães, Portugal, 24-25 September 2009
Hyunwook Kim, Scientist, Ph.D.,
Kiril Sokolov, Research Engineer, M.S.,
Manfred N. Partl, Head of Laboratory, Dr.Sc.
Empa, Swiss Federal Laboratories for Materials Testing and Research
Materials Sci ence & Technolog y
Outline
1. Introduction
2. Materials
3. Experimental program
4. Testing results
5. Summary and Conclusion
6. Ongoing Research on 4PB
Materials Sci ence & Technolog y
IntroductionFour-point bending beam (4PB) tests have been widely used in many countries
to obtain complex modulus and to predict fatigue behavior of bituminous
materials.
In Switzerland, two-point bending beam (2PB) tests and co-axial shear tests
(CAST) have been practically used for predicting the stiffness and fatigue
behavior of bituminous materials.
Recently, a Swiss research project, Performance Orientated Specification for
Bituminous Mixtures VSS 2006/503, was initiated to compare two different test
methods (2PB and 4PB) and to standardize 4PB tests in Switzerland.
Before initiating the research project, some initiative verification tests were
conducted with mastics asphalt in 4 different test methods and a 4PB aluminum
bar.
Materials Sci ence & Technolog y
Materials
SN 640 441a (EN 13108-6: 2006)
Materials Sci ence & Technolog y
Experimental Program
Test method Geometry (mm)UCT D=50, H=100IDT D=100, H=40
CAST Douter=150, Dinner=56, H=404PB L=500, W=H=50
where, D is a diameter, H is a height or a thickness, L is a length, W is a width, Douter is a outer diameter, and Dinner is a inner diameter.
Temperature, °C -20, -10, 0, 10, 20
Frequency, Hz 0.01, 0.1, 1, 5, 10
Test Methods and Specimen Geometries (EN 12697-26, 2004)
Test Conditions CAST
UCT4PB
IDT
Sinusoidal strain amplitude: 50μm
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y6
Co-Axial Shear Tests (CAST)
*)(* GAF
Ga
a
δ=
The CAST was designed at Empa in the 1980s and hasbeen continuously developed further and improved (Gubler etal. 2005, Sokolov et al. 2005, and Kim et al. 2009).
where, G* = Complex modulus in shear, Fa = Force amplitude along the steel core, δa = Displacement amplitude along the steel core, A(G*) = Coefficient function derived from FEA by recursive iteration, Poisson’s ratio of 0.38 was assumed.
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y7
0 40 190 290 440
50
L=400500
50
Dimension: 50 x 50 x 500 (B x H x L)Extended Size (B, H): 30mm – 67mm
Test Set-up
Specimen
Four-Points Bending Beam (4PB) Tests• The test set-up was made by Junker in 1987 and has been modified until now.• Recently, we completed the operating program by LABVIEW for 4PB tests and made
additional holding clamps to cover a wide range of specimen size.
Strain amplitude
( m)
Predicted Complex modulus
(GPa)
Error(%)
Targeting Complex modulus
(GPa)50 72.10 0.13 72.2
* Frequency range (Hz): 1, 5, 10, 20, 30
Verification with a EMPA aluminum bar
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y
1.E+01
1.E+02
1.E+03
1.E+04
1.E-07 1.E-05 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 1.E+09
Frequency (Hz)
Com
plex
mod
ulus
(Mpa
)
-20°C
-10°C
0°C
10°C
20°C
Sigmoidal
1.E+01
1.E+02
1.E+03
1.E+04
1.E-07 1.E-05 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 1.E+09Frequency (Hz)
Com
plex
mod
ulus
(Mpa
)
-20°C-10°C0°CSigmoidal
Fitted Mastercurves of 4 Different Tests
1.E+01
1.E+02
1.E+03
1.E+04
1.E-07 1.E-05 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 1.E+09Frequency (Hz)
Com
plex
mod
ulus
(Mpa
)
-20°C
-10°C
0°C
10°C
20°C
Sigmoidal
IDT
CAST 4PB
1.E+01
1.E+02
1.E+03
1.E+04
1.E-07 1.E-05 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 1.E+09Frequency (Hz)
Com
plex
mod
ulus
(Mpa
)
-20°C
-10°C
0°C
10°C
20°C
Sigmoidal
UCT
Unexpected results at 10°C & 20°C
Rtemp = 0°C
Rtemp = 0°C
Rtemp = 0°C
Rtemp = 0°C
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y
Comparison Results
1.E+01
1.E+02
1.E+03
1.E+04
1.E-07 1.E-05 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07Reduced Frequency (Hz)
Com
plex
Mod
ulus
(MP
a)
UCTIDTCAST4PB
1.E+01
1.E+02
1.E+03
1.E+04
0 10 20 30 40 50 60Phase Angle (°)
Com
plex
Mod
ulus
(MP
a)
UCTIDTCAST4PB
)log(log1*log
Tr afeE +−+
+= γβ
αδ
Fitted by a Sigmoidal Function(Fonseca and Witzack, 1996)
Unstable mastics asphalt at high temperature? (from Solid to Fluid)
Different testing mode or boundary conditions? (Comp. Vs. Shear / Bending)
Different specimen geometry? (Force movement, Volume of strain zone, Size-effect)
where, E* = Complex modulus, δ = Parameterdescribing the minimum value of G*, fr =Frequency of loading at the referencetemperature, α = Parameter describing the spanbetween max and min value of G*, β, γ =Parameter describing the shape of the sigmoidalfunction, aT = Shift factor, determined withWilliams-Landel-Ferry (WLF) relationship.
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y
• Testing program and test set-ups for 4PB was successfully implemented and verified
with an aluminum bar in Switzerland.
• Four different test methods for determining the complex modulus were compared
with sigmoidal fitted mastercurves and black diagrams. Reasonably, complex
modulus tests were comparable but there were increased discrepancies at high
temperatures, above 10°C.
• However, all results were limited to mastics asphalt, MA8. It must be checked out for
different mixture types to make some conclusions. Also, it might be interesting to
investigate the fatigue behavior of bituminous materials with different fatigue tests.
(Related references: Beneditto et al. 2001 (Stiffness), 2004 (Fatigue) from RILEM studies)
Summary and Conclusions
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y
Ongoing Research on 4PB: Program
EMPA LAVOC Notes
Number of Mixture 12 12 2 WC + 4 BC + 4 Base C + 2 LAB (EME C1 and EME C2)
Number of Samples(18 required in EN) 18 18 Total: 18 per each mixture,
4 Modulus + 14(4) Fatigue
Experimental Test 4PBB 2PBB European Standard Tests(Specimen Dimension)
Test Conditions(Stiffness)
10, 15, 20 °C3, 10, 25 Hz
10, 15, 20 °C3, 10, 25 Hz 4 replicates
Test Conditions(Fatigue)
20 °C30 Hz
10 °C25 Hz 6 replicates with 3 strain levels
• Where, 4PBB: 4 point bending beam, 2PBB; 2 point bending beam• Where, WC: wearing coarse, BC: binder coarse
VSS 2006/503, Performance Orientated Specification for Bituminous Mixtures
18 specimens *12 mixtures = 216 specimens
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y
Ongoing Research on 4PB: Field SamplesMaterials Layer
DenominationDepth[mm]
Layingyear Section Layer
Field Cores
AC B 22 60 1989 A9 Conthey-Sion Binder-1AC T 22 90 1989 Base-1PA 11 50 2007 A2 Bellinzone Sud-
Bellinzone NordWearing-1
AC B 22H 90 2007 Binder-2AC T 22H 70 2007 Base-2SMA 11 40 1998 A3 Aargau Wearing-2
AC 22 90 1998 Binder-3AC MR 8 30 2008 Bern Wearing-3
AC 22 S 70 2008 Binder-4AC 22 S
(AC B 22 H) 80 2008 Aargau:N1/05 Limmattal
Binder-5
AC MR 11 35 1999A1 Yverdon-Berne:Tronçon Yverdon-
Arrissoules
Wearing-4
AC 11 40 1999 Binder-6AC EME 22 80 1999 Base-3
AC F 32 105 1999 Subbase-1PA 11 45 1999
A1 Yverdon-Berne: Tronçon Payerne-Avenches:
Wearing-5
AC 16S 45 1999 Binder-7AC B 22 80 1995 Base-4
110 1994 Subbase-2Laboratory Mix EME C1 2009 LAB-1
EME C1 2009 LAB-2
Materials Sci ence & Technolog yMaterials Sci ence & Technolog y13
Example: Micromechanical Fracture Model
(a) Microstructure and Crack Propagation
Fracturing in aggregates
Total: 149,922 particles, 298,855 contacts
Kim et al., Materials and Structures, Vol.42, pp.677-689, 2009.Kim and Buttlar, Int. J. Solids and Structures, Vol.46, 2593-2604, 2009.
External
Fracture
Frictional
Strain
Materials Sci ence & Technolog y
Thank You!!!Thank You!!! hyunwook.kim@empa.ch
14
Full-Scale APTSmall-Scale APT
Reinforcement
3D
2D
Fracture Test
Fatigue Test
Laboratory Tests
Modulus Test
Nano - Micro - Meso
X-ray CT
Full-Scale
Visualization
Leys 2009
FEM
DEM
FEM
DEM
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