Dynamic Modulus Testing of Asphalt Mixtures
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Transcript of Dynamic Modulus Testing of Asphalt Mixtures
Dynamic Modulus Testing of Dynamic Modulus Testing of
Asphalt MixturesAsphalt Mixtures
Mihai O. MarasteanuTim Clyne
University of Minnesota
IntroductionIntroduction
Superpave mix design procedureProduct of SHRP
Different design levels based on traffic levelVolumetric mix design (<106 ESALS)Intermediate analysis (up to 107 ESALS)Complete analysis (> 107 ESALS)
IntroductionIntroduction
Superpave volumetric mix designNo mechanical test to check performance!!!–Marshall method included mechanical test
In the past years comprehensive research efforts to develop
A simple performance test (SPT)To provide material parameters for use in
pavement design (AASHTO 2002)
Introduction Introduction
Recent research efforts (NCHRP 9-19, 1-37A) indicate that
Complex Dynamic Modulus is a strong candidate for both pavement design and SPT
Complex Dynamic ModulusComplex Dynamic Modulus
Not a new concept (Papazian, 1962)Different research projects over the years
Various combinations of frequencies and temperaturesCompression, tension-compression, tension
Most comprehensive in the past yearsProfessor Witzack and his research team–Compression
– Uniaxial loading– Triaxial loading
BackgroundBackground
Based on linear viscoelasticity conceptsControlled sinusoidal load applied to cylindrical
specimenDeformation (strain) measured at different
locations on the sampleTwo fundamental parameters determined–The absolute value |E*|–Phase angle, δ
Test SetupTest Setup
2 LVDT’s4 specimens
3 LVDT’s2 specimens
Experimental DataExperimental Data0.1 Hz @ 24.3°C
0.0
0.5
1.0
1.5
2.0
2.5
100.2 105.2 110.2 115.2 120.2 125.2 130.2 135.2 140.2 145.2 150.2 155.2Time, sec
Forc
e, k
N
0.100
0.105
0.110
0.115
0.120
0.125
0.130
0.135
0.140
0.145
Exte
nsom
eter
Dis
plac
emen
t, m
m
Sample PreparationSample PreparationSample preparation under comprehensive investigation (NCHRP 9-29)Typical gyratory sample not homogeneous
Density gradients–Across diameter (Surface vs. Interior)Top and bottom vs. Interior
Coring procedure recommended:Prepare tall 6” gyratory specimenObtain 4” by 6” tall test specimen
Sample PreparationSample Preparation
Sample PreparationSample PreparationCoring procedure
Difficult to performPossible solution
Use slender 4” mold
AASHTO 2002AASHTO 2002
Dynamic modulus of asphalt mixturesCritical parameter in the design
Difficult to obtain in the laboratoryLink it to properties of components–Components properties easier to determine
Witczak predictive equationRegression techniques developed from–2750 measurements–205 different asphalt mixtures
Mixture Master CurveMixture Master Curve
Simple Performance TestSimple Performance Test
W1: SPT for Permanent Deformation Based Upon Static Creep/Flow Time StrengthW2: SPT for Permanent Deformation Based Upon Repeated Load TestX1: SPT for Permanent Deformation Based Upon Dynamic ModulusX2: SPT for Fatigue Cracking Based Upon Dynamic ModulusA1: Dynamic Modulus of Asphalt Mixtures and Master Curves
SPT SelectionSPT Selection
Recent study shows that|E*| from unconfined test performed at 54.4C
correlates best with rutting–Confinement may be required for SMA and open-graded mixtures|E*| good indicator of fatigue cracking|E*| not a good indicator for thermal cracking–Need Fracture Mechanics
ConclusionsConclusions
Dynamic Complex Modulus critical parameter for design and specificationsSample preparation and testing protocol detailed in AASHTO draft test protocols
Coring vs. slender mold Extensive validation required
Predictive equationDesign parameterPerformance specification
Thank YouThank You