Block 3 SP 14
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Transcript of Block 3 SP 14
Asphalt Binder General Rheology 1
General Rheology
Senior/GraduateHMA Course
Asphalt Binders General Rheology 2
Rheology
• Rheology:– the study of flow and deformation
• Constitutive relations– fundamental relationships between
force and deformation
Asphalt Binders General Rheology 3
Rheometers
• Equipment used to measure rheology• Shear rheometers
– Drag flow– Pressure driven flows
• Rheometers for measuring stiffness and strength– Bending beam– Direct tension
Asphalt Binder General Rheology 4
Shear Rheometers
Asphalt Binders General Rheology 5
Drag Flow Rheometers
• Sliding plate
Asphalt Binders General Rheology 6
Schematic of Sliding Plate Viscometer
(not to scale)
Chart Recorder
Asphalt Binders General Rheology 7
Assumptions
• Steady, laminar flow, isothermal flow• No radial or vertical flow• Negligible gravity and end effects
Asphalt Binders General Rheology 8
Concentric Cylinder
Drag Flow Rheometers
RMi
Ri2 L
R
Ro - Ri
Narrow gaps: Ri / Ro > 0.99
Asphalt Binders General Rheology 9
Drag Flow Rheometers
• Cone and Plate
Similar triangles for shear flow
Homogeneous flow
Asphalt Binders General Rheology 10
Drag Flow Rheometers
• Parallel Plate
Shear flow varies with gap height and radius
Non-homogeneous flow
Asphalt Binders General Rheology 11
Assumptions
• Steady, laminar, isothermal flow• Negligible body forces• Cylindrical edge
Asphalt Binders General Rheology 12
1 cycle
TimeAA
B
C
CA
B
Fixed Plate
Oscillating Plate
Test operates at 10 rad/secor 1.59 Hz
360o = 2 p radians per circle1 rad = 57.3o
Asphalt Binders General Rheology 13
Elastic Viscous
TimeA
A
B
C
Strain
Strain in-phase = 0o
Strain out-of-phase = 90o
Asphalt Binders General Rheology 14
Viscous Modulus, G”
Storage Modulus, G’
Complex Modulus, G*
Complex Modulus is the vector sum of the storage and viscous modulus
Asphalt Binders General Rheology 15
Master Curves• DSR testing can be used to develop master
curves– Need range of temps and frequencies at
each temperature• Information
– Affect of loading time on asphalt binder stiffness
– Estimate of thermal coefficient of expansion
Asphalt Binders General Rheology 16
Equipment Example
Asphalt Binders General Rheology 17
Equipment Examples
Asphalt Binders General Rheology 18
25 mm Plate with Sample
Equipment Example
Asphalt Binders General Rheology 19
Pressure Driven Rheometers
• Vacuum Viscometer
Velocity Profile Shear Stress Profile
Asphalt Binders General Rheology 20
Viscometer Tube
• Asphalt Institute Tube
Asphalt Binder General Rheology 21
Stiffness and Strength Rheometers
Asphalt Binders General Rheology 22
Bending Beam Rheometer
Air Bearing
Load Cell
Deflection Transducer
Fluid Bath
Computer
Asphalt Binders General Rheology 23
Bending Beam Rheometer
• S(t) = P L3
4 b h3 (t)
Where:S(t) = creep stiffness (M Pa) at time, tP = applied constant load, NL = distance between beam supports (102 mm)b = beam width, 12.5 mmh = beam thickness, 6.25 mmd(t) = deflection (mm) at time, t
Asphalt Binders General Rheology 24
Bending Beam Rheometer• Evaluates low temperature stiffness properties
– Creep stiffness– Slope of response (called m-value)
8 15 30 60 120 240
Log Creep Stiffness, S(t)
Log Loading Time, t (sec)
Asphalt Binders General Rheology 25
Direct Tension Test
Le
Stress = = P / A
Strainf
L
Load
f
Asphalt Binders General Rheology 26
Equipment Example
Cooling System
Fluid BathLoading
Ram
Asphalt Binders General Rheology 27
Direct Tension Test
Asphalt Binder General Rheology 28
QUESTIONS?