Innovations on the Asphalt Mix Design for the Rehabilitation of National Route 3 between
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Innovations on the Asphalt Mix Design for the Rehabilitation of National Route 3 between Mariannhiill and Key Ridge. Jaco Liebenberg Dennis Rossmann Philip Joubert. Overview. Introduction to project Structural design limitations Mix design requirements Mix design process

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Jaco Liebenberg Dennis Rossmann Philip Joubert

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Jaco liebenberg dennis rossmann philip joubert

Innovations on the Asphalt Mix Design for the Rehabilitation of National Route 3 between Mariannhiill and Key Ridge

Jaco Liebenberg

Dennis Rossmann

Philip Joubert


Overview

Overview

  • Introduction to project

  • Structural design limitations

  • Mix design requirements

  • Mix design process

  • Mix design performance tests & results

  • Construction


Introduction

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)

13 mm Bitumen rubber seal

40 mm AC

40 mm AG

125 mm AC

300 mm C3 subbase

150 mm G7 selected

CBR 3 subgrade


Introduction1

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


Pavement design options

Pavement Design Options

? mm Concrete overlay

? mm overlay

40 mm AC

125 mm AC

300 mm C3 subbase

150 mm G7 selected

CBR 3 subgrade


Pavement design options1

Pavement Design Options

40 mm AC

125 mm AC

300 mm C3 subbase

150 mm G7 selected

CBR 3 subgrade


Pavement design options2

Pavement Design Options

300 mm C3 subbase

150 mm G7 selected

CBR 3 subgrade


Structural design

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


Mix design requirements

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


Mix design

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%


Trial sections

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


Deformation and rutting resistance

Deformation and rutting resistance

  • MMLS testing and Hamburg wheel tracking tests

    • Also discussed in paper by Hugo et.al


Fatigue resistance

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


Adopted mix design

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


Construction

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


Conclusions

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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