Stiffness Comparisons of Mastics Asphalt in Different Test ... · Stiffness Comparisons of Mastics Asphalt in Different Test Modes 2 nd. Workshop on 4PB at Guimarães, Portugal, 24-25

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


Outline

1. Introduction

2. Materials

3. Experimental program

4. Testing results

5. Summary and Conclusion

6. Ongoing Research on 4PB


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

SN 640 441a (EN 13108-6: 2006)


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.


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


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


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


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.


• 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


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


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


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


Thank You!!!Thank You!!! [email protected]

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

Documents

Stiffness Comparisons of Mastics Asphalt in Different Test ... · Stiffness Comparisons of Mastics Asphalt in Different Test Modes 2 nd. Workshop on 4PB at Guimarães, Portugal, 24-25