1. 1Simulation of compaction of asphalt concrete
Alieh Alipour
Simulation of compaction
of asphalt concrete
Alieh Alipour
Delft University of Technology
Section of Pavement Engineering

2. 2Simulation of compaction of asphalt concrete
Alieh Alipour
Simulation
No-Tension
characteristics
of aggregates
Simulation
Compaction
of asphalt
concrete layer

3. 3Simulation of compaction of asphalt concrete
Alieh Alipour
Compaction
Reduction of air voids in hot mix asphalt by applying force
Desired Density

4. 4Simulation of compaction of asphalt concrete
Alieh Alipour
 Increase stability and strength
 Decrease moisture damage
 Decrease rutting and consolidation by traffic
Effect of compaction on pavement performance
Low level of
compaction
high level of
compaction

5. 5Simulation of compaction of asphalt concrete
Alieh Alipour
Important parameters in compaction
 Composition of asphalt mixture
 Mixture with high volume of natural sand and soft
bitumen
 Mixture with high volume of crushed aggregates and
stiff bitumen

6. 6Simulation of compaction of asphalt concrete
Alieh Alipour
Important parameters affecting compaction
 Temperature
 Initial mixture temperature
 Base temperature
 Air temperature
 Wind speed
 Layer thickness
Compactioneffort
Mix temperature in ⁰C
End of Compaction
Favourable Compaction
Temperature
Start of Compaction
40 60 80 100 120 140 160 180 200

7. 7Simulation of compaction of asphalt concrete
Alieh Alipour
Important parameters in compaction
 Type and magnitude of applied load
 Static compaction
 Tandem rollers
 Pneumatic tired rollers
 Vibratory compaction

8. 8Simulation of compaction of asphalt concrete
Alieh Alipour
Level of compaction
Void content (%)
Density (kg/m3 )
Specific volume (%)
volume of voids in mixture
100%
volume of total mixture including air
aV  
 
3
weight of the material kg
volume of the material [m ]
 
total volume of mixture
100%
volume of solid part of the mixture
v  

9. 9Simulation of compaction of asphalt concrete
Alieh Alipour
Methods of compaction
Laboratory
compaction
method
Field
compaction
method
Marshal Superpave

10. 10Simulation of compaction of asphalt concrete
Alieh Alipour
Methods of measuring compaction
Laboratory
compaction
method
Field
compaction
method
Modelling
compaction
(FEM)Aggregate
properties
Bitumen
properties
Environment
information
Type of roller
Number of
passes
Suitable mix
design

11. 11Simulation of compaction of asphalt concrete
Alieh Alipour
Constitutive Model
 Phase 1 : Aggregates matrix (Elasto-Plastic)
 EffectofPressureontangentmoduli
 Effect of void reduction

12. 12Simulation of compaction of asphalt concrete
Alieh Alipour
Constitutive Model
 Phase 2 : Bitumen (Visco-Elastic)
Viscosity
Temperature in ⁰C

13. 13Simulation of compaction of asphalt concrete
Alieh Alipour
Pressure dependent elasticity
p
p
p
p
p
Bulk Modulus (K)
Pressure dependent
force
Shear Modulus (G)
Constant

14. 14Simulation of compaction of asphalt concrete
Alieh Alipour
Loading-unloading curve
lnv
ln( )p
Normal consolidation line
Swelling line
Plastic volume
changing
Elastic volume
changing
Nonlinear elastic law
Triaxial test
device
2p1p

15. 15Simulation of compaction of asphalt concrete
Alieh Alipour
2J
1I
Yield surface for aggregates matrix
2 2 2
2 1 2 2 3 3 1
1
( ) ( ) ( )
6
J           
1
2
3
2
1
Invariants of stress tensor
1 1 2 3
1
( )
3
I       Yield surface
(growth)
1 1I I 

16. 16Simulation of compaction of asphalt concrete
Alieh Alipour
Hardening rule based on experimental data
lnv
ln( )p
2J
1I
Hardening Law
Loading-
unloading
curve
Yield
surface

17. 17Simulation of compaction of asphalt concrete
Alieh Alipour
Results
Stress-Strain curve for hydrostatic test
P
P
P

18. 18Simulation of compaction of asphalt concrete
Alieh Alipour
Results
Equivalent Plastic Strain development
for hydrostatic test
P
P
P

19. 19Simulation of compaction of asphalt concrete
Alieh Alipour
Conclusions and future plans
 Develop a model to simulate no-tension characteristics of unbound
aggregates in base and subbase layer
 Develop a model to simulate compaction of aggregates (elasto-plasticity)
 Consider the effect of viscosity and temperature to simulate compaction
of asphalt mixture (elasto-visco-plasticity)
 Evaluate the model with experimental data
 Develop CST (Compaction Simulation Tool)

20. 20Simulation of compaction of asphalt concrete
Alieh Alipour
a.alipour@tudelft.nl