Bituminous Stabilized Materials Guideline

Project Initiated By:

Gautrans

Sabita

The Need for Recycling Alternatives

Percentage of Designs in TRH4 Catalogue for > 3 msa

10% 20% 30% 40% 40% 50% 60%

G1 base on cemented subbase

> 100 mm Asphalt on cemented

subbase

> 400 mm Cemented Base

G1 or G2 base on unbound subbase

300 to 350 mm Cemented base &

subbase

Current Guidelines: Main Deficiencies

Mix Design Lack of a suitable curing method Lack of a suitable Shear Strength test Lack of criteria to assess durability & flexibility

Structural Design Very Conservative designs Need to expand knowledge base and incorporate

long term field data

Project Structure

Mix Design Structural DesignPhase 1: Inception Study

Mix DesignStructural

Design

Phase 2: Development of Methodologies

Phase 3: Guideline

Compilation & Review

Selection Criteria

Mix Design Guidelines

Structural Design Issues

Construction Issues

Guideline Finalization & Review

Tasks for Phase 2• Mix Design

– Adapt triaxial test and classification limits– Develop durability test and classification limits– Standardize specimen preparation, curing,

compaction & testing

• Structural Design– Expand LTPP database– Develop and calibrate material classification

method and pavement design method

Crushed stone

CTB

Natural gravel

ETB

Support

3 6 9 12 15 18 21 24Section Age

YearsMESA Accommodated to Date

N12-19 (1)

N12-19 (2)

N1-13&14

N2-16

30

30

25

25

N1-1 20

N3-4 17

19N7-7

P23/1 13

D2388 8

N4-5X (20-25) 8

8N4-5X (27-30)

N4/1 6

MR27 17

MR 504 (1)

P24/1

MR 504 (2)

MR 504 (3)

Same-Himo (1)

Same-Himo (2)

Same-Himo (3)

10

6

10

10

11

11

11

LTPP

3 6 9 12 15 18 21 24Section MESA Accommodated Age

Years3 6 9 12 15 18 21 2490 Surfacing200 ETB150 Lime stabilized base150 Lime stabilized base

N3 HVS (1) 0

N3 HVS (2) 0

N3 HVS (3) 0

N3 HVS (5) 0

N2-16 (322A2) 8

P9/3 (372A3) 0

P9/3 (373A3) 0

P9/3 (374A3A) 0

P9/3 (374A3B) 0

P9/3 (375A3) 0

P9/3 (376A3) 0

D2388 (397A4) 0

D2388 (403A4) 1

D2388 (407A4) 2

D2388 (408A4) 3

P243/1 (409A4) 0

P243/1 (410A4) 0

P243/1 (411A4) 1

N7 (415A5) 0

P243/1 (412A4) 1

N7 (416A5) 0

N12-19 (415A5) 30

Crushed stone

CTB

Natural gravel

LTB

Support

HVS

Structural Design MethodVision:

• Depend on Rational Inputs: Determined from field tests using a specific

procedure Direct linkage with specifications

• Clarity and Transparency Traceable validation Implements design fundamentals

• Straightforward Implementation Requires no specialist software Reliable and Robust

Design Outputs & Expectations

Cost, Effort & Experience Needed

Design Method Outputs

Reliability: E.g.:Is this design suitable for traffic of 3 to 8 mesa?

Life Cycle: How will the pavement fail? How can it be rehabilitated?

Sensitivity: What layers/parameters are most critical to prevent premature failure?

Optimization: What can be done to minimize costs at reasonable risk?

Prediction: How will rut depth, riding quality etc develop over time? Requires simulation

Development Approach

CBR 7-15%

> 200 mm G6

130 mm C4

200 mm BSM 1

Shear Potential

Range of Traffic Accommodated

Rut situation, RQ situation

Cracking situation

Need for rehabilitation

Area = Shear Potential “Fingerprint”

System Performance Indicators

System Behaviour Indicator ???

Cu

mu

lativ

e T

raffi

c Failed Condition

Good Condition

Warning Condition

Design Catalogue Structures

“Fingerprint” Indicator

Conclusion• Structural Design:

– Concept finalized March 2007– Pilot implementation & refinement Mar ’07 to

Jan ‘08

• Mix Design Protocols (2007)– Focus on Shear & Durability– Improved criteria and classification limits – Longer term testing and implementation of new

tests…(2008+)

Design Methodology ConceptTraffic Accommodated (mesa)

1

3

10

30

100 - 200 mm BSM on G7+

support

200 - 300 mm BSM on G6+

150 - 200 mm BSM on 150 mm

Stabilized Support

150 - 200 mm BSM on >250 mm

Stabilized Support