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HMA Characterization Permanent Deformation 1
Permanent Deformation
Senior/GraduateHMA Course
HMA Characterization Permanent Deformation 2
Permanent Deformation
HMA Characterization Permanent Deformation 3
Test Methods
• Gyratory Shear Compactors• Loaded Wheel Testers• Simple Shear Tester• Uniaxial and Triaxial
HMA Characterization Permanent Deformation 4
Terms
• Uniaxial– Vertical axial load only – no confining
pressure• Triaxial
– Both vertical and horizontal pressure used•Horizontal pressure used to
simulate field conditions of lateral support
HMA Characterization Permanent Deformation 5
Terms
• Creep– Static load applied over some time
interval•Usually 1 hour or more•Vertical deformation measured
• Creep recovery•Load removed and rebound of
material measured
HMA Characterization Permanent Deformation 6
Terms
• Repeated loading– Step load followed by a rest period
•Load from 0.05 to 3 seconds•Rest
–From 0.6 to 1 minute– Typical = 0.1 second load & 0.9 sec
rest
HMA Characterization Permanent Deformation 7
Terms
• Dynamic loading– Cyclic loading
•Can be all compression or include stress reversal
–Tension to compression cycles»Simulates stress reversal seen
in pavement as tire passes a point
HMA Characterization Permanent Deformation 8
Loaded Wheel Testers
Asphalt Pavement Analyzer (APA)
Hamburg Wheel Tracking (HWT)
Purdue Wheel Tracker (PurWheel)
LCPC Wheel Tracker (LCPC)
Mobile Load Simulator (MLS) - 1/3 scale
HMA Characterization Permanent Deformation 9
Asphalt Pavement Analyzer
HMA Characterization Permanent Deformation 10
Asphalt Pavement Analyzer
HMA Characterization Permanent Deformation 11
Asphalt Pavement Analyzer
HMA Characterization Permanent Deformation 12
Typical APA Results
0
2
4
6
8
10
0 2,000 4,000 6,000 8,000 10,000Numbers of Load Cycles
APA R
ut
Depth
, m
m
Good HMA Poor HMA
Example of 5 mm Max Limit
HMA Characterization Permanent Deformation 13
Loaded Wheel Testers
Parameters GLWT APA
Specimens 3 Beams 6 Gyratory
Air Voids, % 4 or 7% 4 to 7%
Load, N (lb) 445 (100) 445 (100)
Hose Press kPa (psi) 690 (100) 690 (100)
Conditioning dry wet or dry
Temperature, oC (oF) 35 to 60 (95 to 140) 40 to 64 (105 to 147)
No. of Cycles 8,000 8,000
HMA Characterization Permanent Deformation 14
Asphalt Pavement Analyzer• Three stages in deformation vs passes
0
5
10
15
20
25
0 2,000 4,000 6,000 8,000 10,000
Wheel Passes
Per
man
ent
Def
orm
., m
m
Secondary
Tertiary
Primary
HMA Characterization Permanent Deformation 15
Hamburg
HMA Characterization Permanent Deformation 16
PurWheel
HMA Characterization Permanent Deformation 17
PurWheel
HMA Characterization Permanent Deformation 18
Loaded Wheel Testers
Parameters Hamburg PurWheel
Specimens 2 slabs 2 slabs
Air Voids, % 7 + 1% Varies Load, N (lb) 175 (385) 175 (385)
Wheel Steel Wheel Pneumatic tire 793 kPa (115 psi)
Conditioning wet or dry wet or dry
Temp., oC (oF) 25 to 70 (77 to 158) Variable
No. of Cycles 20,000 or 20 mm rut 20,000 or 20 mm rut
HMA Characterization Permanent Deformation 19
LCPC (French unit)
www.lcpc.fr/LCPC/English/Presentation
HMA Characterization Permanent Deformation 20
US Corps of Engineers Gyratory• Originated at the US Corps of Engineers
Waterways Experiment Station • Generally applicable to dense-graded mixes
– May not be strictly applicable to mixes that are not sensitive to bitumen content
• Can get Mohr’s circle information
HMA Characterization Permanent Deformation 21
US Corps Gyratory (Old)
HMA Characterization Permanent Deformation 22
US Corps Gyratory (New)
HMA Characterization Permanent Deformation 23
Simple Shear Tester (SST)
• Simple Shear Tests– Permits controlled rotation of
principal axes of stress and strain– Assumes shear deformation rather
than densification is the primary rutting mechanism
9
HMA Characterization Permanent Deformation 24
SST
Prepared sample
Computer control and chamber
HMA Characterization Permanent Deformation 25
SST
Empty chamber ready for sample
Sample mounted in chamber and ready to test
HMA Characterization Permanent Deformation 26
Uniaxial and Triaxial Testing
www.mts.com
HMA Characterization Permanent Deformation 27
QUESTIONS ?