innovations on the asphalt mix design for the rehabilitation of national route 3 between...
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![Page 1: Innovations on the Asphalt Mix Design for the Rehabilitation of National Route 3 between Mariannhiill and Key Ridge Jaco Liebenberg Dennis Rossmann Philip](https://reader038.vdocuments.mx/reader038/viewer/2022110116/551b72ef550346a10a8b4a60/html5/thumbnails/1.jpg)
Innovations on the Asphalt Mix Design for
the Rehabilitation of National Route 3
between Mariannhiill and Key Ridge
Jaco Liebenberg
Dennis Rossmann
Philip Joubert
![Page 2: Innovations on the Asphalt Mix Design for the Rehabilitation of National Route 3 between Mariannhiill and Key Ridge Jaco Liebenberg Dennis Rossmann Philip](https://reader038.vdocuments.mx/reader038/viewer/2022110116/551b72ef550346a10a8b4a60/html5/thumbnails/2.jpg)
Overview
• Introduction to project• Structural design limitations• Mix design requirements• Mix design process• Mix design performance tests & results• Construction
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CBR 3 subgrade
Introduction
• N3/1&2 Mariannhill – Key Ridge• Main link Durban - Gauteng• Constructed in 1985• 40 to 50 million E80’s• Constructed as• Maintenance
– 1994/5 (+14 years)
• Identified for Rehabilitation– 2006 (+20 years)
150 mm G7 selected
40 mm AG
125 mm AC
300 mm C3 subbase
40 mm AC
13 mm Bitumen rubber seal
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Introduction
• Major typical defects– Rutting in slow lane– Some isolated rutting in middle lane– Cracking and pumping in slow lane
• Design traffic
• Design requirements– Slow lane: Substantial pavement required– Middle lane: Some repairs required– Fast lane: None required
Slow lane Middle lane
15 years 70 million 22 million
30 years 185 million 54 million
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Pavement Design Options
40 mm AC
125 mm AC
150 mm G7 selected
300 mm C3 subbase
CBR 3 subgrade
? mm overlay? mm Concrete overlay
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Pavement Design Options
40 mm AC
125 mm AC
150 mm G7 selected
300 mm C3 subbase
CBR 3 subgrade
![Page 7: Innovations on the Asphalt Mix Design for the Rehabilitation of National Route 3 between Mariannhiill and Key Ridge Jaco Liebenberg Dennis Rossmann Philip](https://reader038.vdocuments.mx/reader038/viewer/2022110116/551b72ef550346a10a8b4a60/html5/thumbnails/7.jpg)
Pavement Design Options
150 mm G7 selected
300 mm C3 subbase
CBR 3 subgrade
![Page 8: Innovations on the Asphalt Mix Design for the Rehabilitation of National Route 3 between Mariannhiill and Key Ridge Jaco Liebenberg Dennis Rossmann Philip](https://reader038.vdocuments.mx/reader038/viewer/2022110116/551b72ef550346a10a8b4a60/html5/thumbnails/8.jpg)
Structural design
• Stabilised subbase performed well– Only localised repairs required– Not thick enough for traffic volume (req 450 mm)
• Asphalt inlay considered most appropriate– Mix design to compliment structural design– Stiff as possible (req: E = 4 000 Mpa)
• Slow lane– Signs of stripping in lower part of layer replace all asphalt– Selective repairs of subbase
• Middle lane– Some cracking and deformation Only repair upper 80 mm
• Fast lane– Only Isolated repairs
• New surfacing over full width
Paper discuss process to consider for restrictions in structural design by optimising the asphalt mix design
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Mix design requirements
• Primary requirements– Rut resistant– Stiff (≈ 4 000 MPa)– Fatigue resistant
• Secondary requirements– Low permeability– Good moisture susceptibility
• Mix design process– Standard mix design process– 2 mix designs in parallel – selection process– Much emphasis on performance testing– Performance tests on mixes from trial sections
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Mix design
• Aggregate and grading – Coarse aggregate quartzite– Fine aggregate: quartzite & tillite mix– Bailey method to determine optimum grading– Contained 15 % RAP
• Binders– Two binders evaluated– A-P1 (4% EVA) with Optimum binder Content @ 4.2%– vs. A-E2 (3.5% SBS) with Optimum binder Content @ 4.4%
• Min component of mix design:– Performance under accelerated testing
• 6 trial sections constructed– Directly north of toll Plaza in slow lane– A-P1 mix: 3.9% 4.2% and 4.5%– A-E2 mix: 4.0% 4.3% and 4.6%
0.01 0.1 1 10 1000
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Sieve Size (mm)
% P
as
sin
g
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Trial sections
• From trial sections (extracted from pavement)– 228 cores– 16 beams
• Tested for– Rut resistance under MMLS and Hamburg wheel tracking– Moisture susceptibility under MMLS and mod. Lottmann– Permeability– Fatigue
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Deformation and rutting resistance
• MMLS testing and Hamburg wheel tracking tests– Also discussed in paper by Hugo et.al
4.2% A-P1
4.5% A-P1
4.3 % A-E2
4.5 % A-E2
MMLS Dry, 7200/hr, 60 °C Yes Yes Yes Yes
MMLS Dry, 2400/hr, 60 °C Yes No Yes No
MMLS Wet, 7200/hr, 60 °C Yes No Yes No
Hamburg Yes Yes Yes Yes
A-P1 (3,9%) A-P1 (4,2%) A-P1 (4,5%) A-E2 (4,1%) A-E2 (4,4%) A-E2 (4,7%)0
0.5
1
1.5
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2.5
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3.5MMLS
MMLS dry @ 7 200/hour
MMLS wet @ 7 200/hour
Mix
Ru
t a
fte
r 1
00
00
0 r
ep
itit
ion
s (
mm
)
A-P1 (3,9%) A-P1 (4,2%) A-P1 (4,5%) A-E2 (4,1%) A-E2 (4,4%) A-E2 (4,7%)0
0.0001
0.0002
0.0003
0.0004
0.0005
0.0006
0.0007Hamburg wheel tracking
Mix
Ru
t ra
te (
mm
/pa
ss
)
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Fatigue resistance
• Coarse rut resistant mixes generally poor fatigue• Beams extracted from pavement
– 6 beams for 4.2% A-P1 tested– 6 beams for 4.3% A-E2 tested
• Fatigue test– 4 point bending beam– Constant strain
10 000 100 000 1 000 000 10 000 0000
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Repetitions
Str
ain
(m
e)
A-P1
A-E2
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Adopted mix design
• A-P1 mix considered most appropriate mix– Better rut resistance– Better moisture susceptibility– Fatigue comparable to A-E2, within acceptable guidelines
• A-E2 probably suitable as well• Performance tests A-P1
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Construction
• High level of control comfort design intent is built• Tight control of
– Mix properties– Compaction
• Ability to project trends and act pro-actively• Construction quality
– No rejected work or rework on Asphalt base– Some issues recently with UTFC currently being investigated
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Conclusions
• Limitations during structural design• Possible to optimise mix design to compliment
structural design– Require cooperation
• Asphalt mix design process– Benefits not a standalone process– Tie in with pavement design
• Attention to mix design – mix appropriate for application – considers unique requirements for application
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