block 28 sp 13
TRANSCRIPT
![Page 1: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/1.jpg)
HMA Characterization Stiffness 1
Stiffness of HMA Mixtures
Senior/GraduateHMA Course
![Page 2: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/2.jpg)
HMA Characterization Stiffness 2
Important for PredictingPavement Performance
• Used to predict:– Critical stresses and strains
• ELSM5• WESLEA
– Fatigue cracking– Permanent deformation characteristics
![Page 3: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/3.jpg)
HMA Characterization Stiffness 3
General Terms
• Dynamic load– Load applied using a
sinusoidal wave form
• Repeated load– Load pulse applied then
removed– Rest period between loads
Load
Load
Time
Time
![Page 4: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/4.jpg)
HMA Characterization Stiffness 4
Elastic Viscous
TimeAA
B
C
Strain in-phase = 0o
Strain out-of-phase = 90o
Dynamic Loading
Strain
Stress
Strain
Stress
![Page 5: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/5.jpg)
HMA Characterization Stiffness 5
Resilient ModulusRepeated Load
Strain
TimeLoad Period
Rest Period
Instantaneous Recoverable
Strain
TotalRecoverable
Strain
![Page 6: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/6.jpg)
HMA Characterization Stiffness 6
Stiffness
• Fundamental to the analysis of pavement response to traffic loading
• Various methods– Axial resilient (ASTM D3497)– Diametral resilient (ASTM D4123)– Flexural dynamic– Shear dynamic
![Page 7: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/7.jpg)
HMA Characterization Stiffness 7
Resilient Modulus
• Axial (without pressure cell)
OEM, Inc., 2000
![Page 8: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/8.jpg)
HMA Characterization Stiffness 8
Axial Resilient Stiffness
10
100
1,000
10,000
0 10 20 30 40 50
Temperature, C
Stif
fnes
s, k
siLow Air VoidsHigh Air Voids
Affect of Temperature and Air Voids
(Tayebali, Tsai, and Monismith, 1994)
![Page 9: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/9.jpg)
HMA Characterization Stiffness 9
Axial Resilient Stiffness
10
100
1,000
10,000
0 10 20 30 40 50
Temperature, C
Stif
fnes
s, k
siOptimumHigh AC Content
Affect of Temperature and Asphalt Content
(Tayebali, Tsai, and Monismith, 1994)
![Page 10: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/10.jpg)
HMA Characterization Stiffness 10
Diametral Resilient Modulus
![Page 11: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/11.jpg)
HMA Characterization Stiffness 11
Diametral Stiffness
10
100
1,000
10,000
0 10 20 30 40 50
Temperature, C
Dia
met
ral R
esili
ent
Mod
ulus
, ks
i
Opt. ACHigh AC
(Tayebali, Tsai, and Monismith, 1994)
Increased AC content = decreased modulus
![Page 12: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/12.jpg)
HMA Characterization Stiffness 12
Diametral Stiffness
10
100
1,000
10,000
0 10 20 30 40 50
Temperature, C
Dia
met
ral R
esili
ent
Mod
ulus
, ks
i
4% Air Voids8% Air Voids
(Tayebali, Tsai, and Monismith, 1994)
Increased air voids = decreased modulus
![Page 13: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/13.jpg)
HMA Characterization Stiffness 13
Diametral Stiffness
10
100
1,000
10,000
0 10 20 30 40 50
Temperature, C
Dia
met
ral R
esili
ent
Mod
ulus
, ks
i
0.5 Hz1.0 Hz
(Tayebali, Tsai, and Monismith, 1994)
No significant influence on frequency (rest period)
![Page 14: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/14.jpg)
HMA Characterization Stiffness 14
Axial vs. Diametral
• Axial more sensitive to air voids than diametral• Diametral stiffness about 35 to 45% greater than axial
stiffness• Elastic modulus difficult to measure even at
moderately warm temperatures (40oC (104oF)) because of excessive sample deformation– Best to limit test temp to < 25oC (77oF)
![Page 15: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/15.jpg)
HMA Characterization Stiffness 15
Flexural Stiffness
Beam
![Page 16: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/16.jpg)
HMA Characterization Stiffness 16
Flexural Stiffness
• Typical beams– 38 x 38 x 381 mm (1.5 x 1.5 x 15 in)
• Testing parameters– 0.1 sec load, 1.67 Hz haversine– range of temperatures
• 0 to 25oC (32 to 77oC)• Used to estimate stiffness at critical strain
anticipated in pavement
![Page 17: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/17.jpg)
HMA Characterization Stiffness 17
Comparisons
0
300
600
900
1,200
Flexural Axial Diametral
8% Air Voids
4% Air Voids
20oC (68oF)
Resilient Modulus, psi
![Page 18: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/18.jpg)
HMA Characterization Stiffness 18
Comparisons
0
300
600
900
1,200
Flexural Axial Diametral
Opt AC
High AC
20oC (68oF)
Resilient Modulus, psi
![Page 19: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/19.jpg)
HMA Characterization Stiffness 19
Dynamic Shear Modulus
Can be conducted over a range of frequencies or at a fixed frequency
![Page 20: Block 28 Sp 13](https://reader036.vdocuments.net/reader036/viewer/2022062419/558e46f41a28ab56268b46d3/html5/thumbnails/20.jpg)
HMA Characterization Stiffness 20
Stiffness
• General conclusions, independent of method used to estimate– Sensitive to:
• Asphalt binder type• Aggregate type• Air-void content• Temperature