effects of specimen compaction on performance ... of specimen compaction on performance...

TECHNISCHE UNIVERSITTECHNISCHE UNIVERSIT ÄÄTT

CAROLOCAROLO --WILHELMINAWILHELMINAzu Braunschweigzu Braunschweig

ISBSInstitut für Straßenwesen

Effects of Specimen Compaction on Performance Characteristics:

Results of Triaxial tests on AC

Konrad Mollenhauer

Update of progress at ISBS




Compaction methods at ISBS

Roller Sector Gyratory Marshall




Compaction of Asphalt mix

Goal: Vm = 4 %




Preparation of specimens

French Roller




Triaxial Tests: EquipmentLV

DT

(ra

dial

)

LVD

T (

radi

al)

LVDT (axial)

LVDT (axial)

rubber membrane hydraulic oil(radial loading)

axial loading

specimen




Triaxial Test: Loading (EN 12697-25)

Axial Stress

Radial Stress

• Sinusoidal axial stress:σa = 0.3 MPa; σb = 0.15 MPa; frequency: f = 10 Hz

• static radial stress:σrad = 0.15 MPa

• Temperature: +50°C• Specimen dimensions:Diameter: 100 mm (MPK: 101.4 mm)Height: 60 mmd/H: 0.6




Triaxial test: Results

• Course of cumulatedaxial strain εax(N):

• creep rate fc,ax(N=1,000)

fc,ax






• creep rate fc,ax(N=1,000)Bε1000,calc

fc,ax

εax = A · NB

ε1000,calc






• creep rate fc,ax(N=1,000)ε1000,calc

• Course of cumulatedradial strain εrad(N):fc,rad(N=1,000)

εax = A · NB

ε1000,calc

εrad

fc,ax

fc,rad




Triaxial Test: Results

( ) axaxaxradrad

axradradax

2 ε⋅σ−ε−ε⋅⋅σε⋅σ−ε⋅σ=µ

εrad

εax

here:σax: axial mean stressσc: radial (confining) stressεax: fc,ax

εrad: fc,rad




Triaxial Tests: cumulated axial strains

French Roller

German Sector

Gyratory

Marshall




Triaxial Test: creep rate fc,1000

French Roller

German Sector

Gyratory

Marshall




Triaxial Test: strain after 1000 cycles ε1000,calcFrench Roller

German Sector

Gyratory

Marshall




Triaxial Tests: cumulated radial strains

French Roller

German Sector

Gyratory

Marshall




Poisson‘s ratio µ




Compaction method or void content?

Further Tests necessary:• Further specimens

available:Marshall: Vm = 2,0 %Gyratory: Vm = 1,6 %

• New specimens- Roller Sector (Vm: 1.5 & 3.5)

(2 new slabs: 25 kg mix)- French Roller with varied

compaction energy?




Comparative test program „Segment Roller Compaction”

Scope:• Roller Sector Compactor Devices are commonly used Europe-

wide• Compaction Procedure varies considerably Objective:• Analysation of impact of given compaction procedure on

mechanical properties of asphalt specimens• Evaluation of reproducibility of Roller Sector compaction Participants:

ISBS (Germany), ISTU (Austria), TUDD (Germany), UVT (Hungary); ifbGauer (Germany); TUD (Netherlands)





AC 11 (bitumen 50/70)

2.476maximum density [g/cm³]

6.0binder content [mass-%]

52softening point Ring & Ball [°C]

50/70binder type

C90/1content of crushed aggregate

53.0 %> 2.0 mm

37.5 %> 0,09 mm & < 2.0 mm

9.5 %< 0.09 mm

[%]

2.698maximum aggregate density [g/cm³]

0,25 0,71 2 5 11,28 160,090

10

20

30

40

50

60

70

80

90

100

Sieve [mm]

pass

ing

[%]

Asphalt Mixture: AC11

Each laboratory uses 2 compaction procedures:1. Common procedure (according German Standard)2. Laboratory standard procedure




German Standard Compaction Procedure

00,10,20,30,40,50,60,70,8

-20 -10 0 10 20 30 40 50

Number of compaction cycles

For

ce p

er c

m

slab

wid

th [k

N/c

m]

Force [kN/cm] Pre-Compaction

Force [kN/cm] Main-Compaction

5

6

7

8

9

10

Hei

ght o

f as

phal

t sla

b [c

m]

Slab height during pre-compaction

Slab-height during main compaction

Pre-Compaction Main-Compaction

Force = 0,1 kN/cm slab width

+0,5 cm / cycle

5 cycles ± 0

-0,5 cm / cycle

Force = 0 kN





Test program:

• Slab compaction: January/February

• Specimen preparation (cores) February/March• Mechanical Tests (Triaxial tests)March/April

• Presentation of Results: May




ATCBM pre-conference workshop

Laboratory compaction of asphalt mixtures for the preparation of specimens for performance-based test methods

Topics:Impact of specimen compaction

- on aggregate structure- on performance properties

Comparability with site compacted asphalt




ATCBM pre-conference workshop

Laboratory compaction of asphalt mixtures for thepreparation of specimens for performance-based test methods

Tuesday, May 26th8 presentations about 20 min (selection accordingsubmitted 2 page abstract)

Deadline for abstract submission: February 15thNotice of Acceptance until March 31st

effects of specimen compaction on performance ... of specimen compaction on performance...

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