Post on 13-Apr-2017
D O T T O R AT O D I R I C E R C A I N I N G E G N E R I A C I V I L E , C I C L O X X V I I
I N D I R I Z Z O I N F R A S T R U T T U R E V I A R I E E T R A S P O R T I
PERFORMANCES AND DURABILITY OF ASPHALT MIXTURES MADE WITH RECLAIMED ASPHALT PAVEMENT
Ph.D. Candidate: Luca Noferini Tutor: prof. Andrea Simone
Reclaimed Asphalt Pavement (RAP)
• Asphalt mix obtained from dismatling / milling of existing asphalt layers
• Made of aggregate and bitumen • 100% reusable and recyclable (European Asphalt Pavement
Association, 2010) to produce new asphalt mixes
Research topic and objectives
USE OF RAP IN NEW ASPHALT MIXES PRODUCED WITH HOT-IN-PLANT TECHNOLOGY
• How much RAP can be incorporated in a new asphalt mix with no negative effects on mix’s performance?
• To what extent RAP affects the final mix’s properties?
PHASE 1: European and Italian context of RAP usage
PHASE 2: Study of RAP influence on a specific asphalt mix
• RAP availability and applications
• Economic and environmental advantages of RAP usage
• Production technologies
RAP applications
Hot, warm, cold asphalt mixes
Bitumen and aggregate
High
Average
Low/cost
Aggregate
None
Granular material (filling)
Landfilling
Value What is reused Application
Pros and Cons of RAP usage
2. Reduced costs of virgin bitumen (5% mass weight / >50% price)
1. Reduce the need of natural and not-renewable resources (aggregate and bitumen)
3. Lower GHG emissions, atmosferic pollution (ground level ozone creation and acidification) related to raw materials supplying
1. Costs for retrofitting of asphalt plants
2. Special handling procedures and management required
3. Strategy (market regulation)
5. RAP mixes are high quality and long lasting products (if...)
4. Public admin. are concerned about RAP mixes performance
39
32 31
22 21 18
15
9
2014 European asphalt production, million tonnes
• European road netword is 5.7 million km long
• 230 million cars and 31 million heavy vehciles
• 40 mil tonnes of asphalt required for road maintenance in Italy
2014 RAP availability in Europe, million tonnes
10.9
9.2 9.0
4.5 3.4
2.3 1.3 1.2 1.0 1.0
0.4
Use or RAP in valuable applications (% of 2014 availability)
100% 100% 95% 90% 85% 85%
75% 64% 63%
54% 50%
6%
• High-value: hot / warm / cold in place / in plant recycing
• Low-value: use as unbound granular material
• No value / cost: landfilling
Percent of available RAP used for different purposes in Europe
Hot Mix Asphalt, 61%
Warm Mix Asphalt, 4%
Cold Recycling, 5%
Unbound Layers, 13%
Other civil eng. applications, 10%
Landifll/other, 7%
Percent of available RAP used for different purposes in Europe (%)
0
10
20
30
40
50
60
70
80
90
100
Hot Mix Asphalt Warm Mix Asphalt
Cold Recycling Unbound Layers
Other civil eng. applications Landifll/other
Experimental programme
4 versions of AC Binder 0/20 @ 0%, 10%, 20% and 30% RAP
Same PSD, 5% air voids and 5% bitumen content
LAB TESTS ON ASPHALT MIXES LAB TESTS ON BITUMEN
Characterization of raw mat.
Mix desing of RAP mixes
Volumetrics
Production of asphalt beams
Fatigue testing (4PB)
Extraction and recovery
Penetration and R&B
Dynamic viscosity
Dynamic Shear Rheometer
ONLY CEN STANDARDISED TESTS!
RAP asphalt mixtures durability
0
20
40
60
80
100
0.01 0.1 1 10 100
Perc
ent
pas
sin
g (%
)
Sieve size, Log (mm)
Mix0 (control mixture) Mix1 (control+10% RAP)
Mix2 (control+20% RAP) Mix3 (control+30% RAP)
Mix Design – Particle Size Distribution of RAP mixes
Total blending RAP/neat bitumen assumed Proportioning with extracted RAP PSD
Mix Design – Total bitumen content of RAP mixes
5.0% 4.5%
4.1% 3.6%
0%
1%
2%
3%
4%
5%
6%
0
10
20
30
40
50
60
Bit
um
en c
on
ten
t (%
by
aggr
egat
e m
ass)
Bit
um
en c
on
ten
t (g
ram
s o
n 1
kg
sam
ple
)
RAP 0/8 RAP 8/12 Virgin 50/70 Virgin bitumen content (%)
Total blending RAP/neat bitumen assumed Proportioning with extracted RAP PSD
75
78
80
83
85
88
90
93
95
98
100
1 10 100 1000
Perc
ent
of
max
imu
m d
ensi
ty ρ
M (
%)
Number of gyrations, Log
Mix Design – Volumetric study with gyratory compactor
Target 5% air voids
0% RAP
30% RAP
• Compactability increase with RAP content • Higher presence of fines with increasing RAP content
Production of samples – Bulk Density of asphalt beams
Mix0 2337
Mix1 2379
Mix2 2359
Mix3 2387
1900
2000
2100
2200
2300
2400
2500
Bu
lk d
ensi
ty (
kg/m
3)
• Density used as parameter to check if materials are comparable • Testing the material vs testing the sample
Wöhler Fatigue lines
1.E+04
1.E+05
1.E+06
1.E+07
10 100 1000
Nu
mb
er o
f cy
cles
to
fai
lure
(N
f20
)
Strain amplitude (με)
Mix0
Mix1
Mix2
Mix3
Mix0 Fatigue Line
Mix1 Fatigue Line
Mix2 Fatigue Line
Mix3 Fatigue Line
0% RAP
30% RAP
• 4PB, strain-controlled, 25 Hz, 10°C at 100, 150, 200 µε, NF 20% • RAP contributes stiffening the neat binder (slope changes with bitumen type) • Mix with 30% RAP shows the longest fatigue life (highest Nf)
Number of cycles to failure
Mix0 - 0% RAP Mix1 - 10% RAP Mix2 - 20% RAP Mix3 - 30% RAP 0.E+00
2.E+06
4.E+06
6.E+06
8.E+06
1.E+07
1.E+07
Load
cyc
les
to f
ailu
re (
Nf2
0)
at
stra
in le
vel o
f 1
00
με
Va= 5.9% BD = 2463 kg/m3
Bc = 5.07%
Va = 4.0% BD = 2477 kg/m3
Bc = 4.97%
Va = 4.9% BD= 2480 kg/m3
Bc = 5.0%
Va= 3.8% BD= 2480 kg/m3
Bc = 5.03%
• Adding up to 20% RAP seems to have no negative effect on mixes’ durability • Higher sensitivity to RAP content than to other material properties (voids) • Mix 3 has the highest results variability
Analysis of fatigue data with RDEC approach
• Same conclusion of Wohler fatigue lines • The RDEC approach is more time-consuming and may be inconsistent
Interaction neat-RAP bitumen
• Laboratory testing on bitumen obtained from prismatic samples with cold extraction method (DCM) and recovered with Rotavapor
Penetration and softening point of recovered bitumen
• RAP bitumen causes hardening of the bitumen blend in proportion to RAP content
Pen at 25°C
Ring & BallMix 0
Mix 1Mix 2
Mix 3RAP
27 25
21 16
7
55 56 57 63 73
Dynamic viscosity at 135, 150, 160 and 170 °C
• Viscosity increases in proportion to RAP % (... above 0.23 Pa*s at 160°C) • No significant changes in viscosity up to 20% RAP content • Increase in RAP-neat bitumen blend viscosity at 30% RAP
0
1
10
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Dyn
amic
vis
cosi
ty (
Pa∙s
)
% RAP
135
150
160
170
RAP BITUMEN NEAT BITUMEN
Bitumen rheology – Complex modulus isochrones
• Hardening and increased elastic response in proportion to RAP content • No effects on blend’s rheology up to 10% RAP, limited effects at 20% RAP • Apparently no brittleness issues at 30% RAP
1.E+02
1.E+05
1.E+08
0 10 20 30 40 50 60 70 80 90
Co
mp
lex
mo
du
lus
|G*|
(Pa
)
Temperature (°C)
B0
B1
B2
B3
BRAPHardening
Bitumen rheology – Phase angle isochrones
• Hardening and increased elastic response in proportion to RAP content • No effects on blend’s rheology up to 10% RAP • Significant effects on bitumen rheology when RAP content is 20% or above
0
2
4
6
8
10
0 10 20 30 40 50 60
Tgδ
Temperature (°C)
B0
B1
B2
B3
BRAP
Increased elastic response
Research findings
1. The specific type of asphalt mixture can be produced with hot-in-plant technology incorporating up to 20% RAP with no detrimental effects on its performance and durability
2. RAP can be incorporated in the investigated mix at percentages up to 10% with no significant effects on bitumen properties. In this case, RAP can be added without the need to perform any additional lab test on the recovered binder
3. For 20% or more of RAP content being incorporated in the new mix, it’s highly recommended to perform lab investigations on the recovered bitumen to determine: penetration at 25°C, softening point and dynamic viscosity at 160°C
Recommendations
1. Standard mix design procedures shall be adjusted for RAP mixes in order to take into account of RAP variability and the presence of aged bitumen
2. The amount of bitumen being added in new mixes shall be calculated considering the contribute of the old bitumen which is present in the RAP aggregate
3. RAP sampling shall be aimed to obtained representative portions of RAP and to avoid segregation to impact samples’ representativeness (see EN 932-1 and 12697-27 for sampling procedures)
4. RAP characterization contributes to limiting its variability making RAP usage reliable and therefore more attractive to public authorities