Transport and Main Roads - aapaqtmr.org · 23-May-12 3 Transport and Main Roads Performance...

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Transport and Main Roads

Insitu Stabilisation


Transport and Main Roads Transport and Main Roads

Erosion


Delaminations

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Transport and Main Roads Block cracking Transport and Main Roads

Punching of stabilised layer



Pavement Design – Cemented Pavements

• Items required:o Accurate traffic data to calculate design ESAso Existing Pavement Structureo Insitu subgrade strengtho Depth of suitable material for stabilisationo Applied load (full standard axle 750kPa tyre pressure)o Stabilised pavement stiffness – Resilient Modulus

(MPa)o Performance criteria???

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Performance Criteria

• Pre-cracking Criteria o CAT I CTB - (310/)12, Modulus 5,000MPa UCS 3 – 4MPa Type 1.1, 1.2, 2.1, 3.1 material

o CAT II CTB - (440/)12 Modulus 2,000MPa UCS 2 – 3MPa Type 1.1, 1.2, 2.1, 3.1 material

UCS 3 – 4MPa other materials (if appropriate for use)

o CAT I and Cat II CTB generally provide insufficient fatigue life in most situations without going to deep lift stabilisation (300mm+) or inclusion of post cracking life in the design calculations.


Post-Cracking Life

• Should only be assumed where there is:o 175mm of cover material (asphalt or granular)

o Geotextile seal or interlayer

o PMB Interlayer (S9S @ 2.5L/m2)

• Post cracking life - 500MPa anisotropic layer (no sublayering)


Performance Warning

• Disasters can occur which may result in a maintenance nightmare for years to come!

Note the strategically placed soft drink can!


Cementitiously Insitu Modified Pavements

• UCS Target 1.5MPa at 7 days (Min 1MPa and Max 2MPa)

• Performance criteria /Design Methodology– ??? Now available

• Generally modeled as a granular layer with a higher modulus (sub layered)

• Extracted field cores indicate that stiffening over time , fatigue could develop if proper design and support conditions are not provided


Roma : Insitu Stabilisation

• 12 projects amounting to 63km of varying construction between June 1997 – Oct 2001

• Construction : 3 Full Width; 9 OWPs

• Subgrade : 4 NonReactive; 8 Reactive

• Additive Type : 6 Cem/Fly; 3 Lime/Fly;

2 Lime/Cem/Fly; 1 Hydrated Lime

• Depth of stabilisation : 6 x 250mm; 6 x 300mm

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Where abouts ?

RomaMiles

Charleville

Cunnamulla


Type of Materials Stabilised• 25% Added Gravel + 25% Exist Gravel + 50% Loam

: 4% C/F• 50% Ridge Gravel + 50% Sandstone : 5% L/C/F

(30/30/40)• 50% Ridge Gravel + 50% Loam : 5% C/F (75/25)• 50% Ridge Gravel + 50% White Rock : 5% C/F

(75/25)• 40% Ridge Gravel + 60% Loam to Clay Loam : 2%

C/F• 50% Loam + 50% Clay : 2.5% C/F• 83% Loam + 17% Clay : 6.5% Hyd Lime


Assessing Performance• Structural Performance :

o Rutting

o Shoving

o Block/Fatigue Cracking

o Pavement Repairs

• Functional Performance :o Longitudinal Cracking

o Vertical Depression at Joint

o Roughness

o Surfacing Defects


Early Performance (2 – 7 yrs) by Design Lab UCS

• Poor Performers : UCS < 0.7MPa

• Fair Performers : UCS 0.7MPa – 1.2 MPa

• Good Performers : UCS 1.2MPa –1.5MPa


Early Performance (2 – 7 yrs) by Stabilisation Depth

• 300mm Depth (6 Projects):o Good Structural = 1 Good Functional = 0

o Fair Structural = 3 Fair Functional = 5

o Poor Structural = 2 Poor Functional = 1

• 250mm Depth (6 Projects) :o Good Structural = 5 Good Functional = 4

o Fair Structural = 1 Fair Functional = 2

o Poor Structural = 0 Poor Functional = 0


Early Performance : Conclusions

• Target 1.0 MPa to 1.5MPa Design Lab UCS

• Plan a Geotextile Seal for stabilised Pavements on Reactive subgrades

• Lime/Flyash (40/60), in economic proportions, struggles to provide UCS

• Depth of 250mm

• Better construction practices to avoid depressed joint

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South of SuratStructural = GoodFunctional = Fair


Block Cracking : North of Roma

Structural = FairFunctional = Fair


94/23A/22 Job – Good Structural: 6.5% Hyd Lime

94/23A/23 Job – Poor Structural: 5% Lime/Flyash (40/60)


Performance Warning

• It is essential that the following items are adequately controlled to achieve the desired outcomes:o Design UCS testing and calculation of design thickness

Determination of the allowable working time

Incorporation of a geotextile seal and PMB interlayer

o Construction Additive content, moisture content, stabilisation depth and

compaction


Typical binder types

• lime

General purpose, Types GP or GBSpecial purpose, Types LH, SR, etcComplying with AS3972

• cement

Hydrate (MRS 11.23)Quicklime (MRS 11.23)


Typical binder types (cont.)

• Ground granulated iron blast furnace slag

(AS 3582.2 )

• Flyash

(AS 3582.1 - fine grade)

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Typical blends

“Slagment” 75 cement : 25 slag cement

“Pozzoment” 75 cement : 25 flyash

“Stabilment” 85 granulated : 15 lime slag

“Triple blends” lime/slag/flyash30/50/20 or 33/33/33 etc.


• WORKING TIME FOR MODIFIED MATERIALS


Definitions - working time (RTA)

(a) Working time for maximum dry density

The working time for maximum density is defined as the time measured from the commencement of the addition of the stabilising agent to the compaction of the stabilised material, which corresponds to 97.0% of the mean value of three determinations of maximum dry density in accordance with RTA T130, for samples compacted one hour after incorporation of the stabilising agent. All samples shall be cured in a loose condition in airtight containers at 23°C 2°C.


Definitions - working time (cont.)

(b) Working time for unconfinedcompressive strength (UCS)

The working time for UCS is defined as the time measured from the commencement of the addition of the stabilising agent to the compaction of the stabilised material, which corresponds to 80% of the mean value of three determinations of UCS in accordance with RTA T131, for samples compacted one hour after incorporation of the stabilising agent. All samples shall be cured in a loose condition in airtight containers at 23°C ± 2°C.


Definitions - working time (cont.)

(c) Nominated working time

The nominated working time is the lesser of the working time determined for either the maximum dry density or the unconfined compressive strength.


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Inglewood – 2001

Fatigue CrackingPossible CTB Patch?

Fatigue Cracking Fatigue Cracking


Rainbow Beach – 2003


Allora - 2002

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Transport and Main RoadsGuide to selecting method of stabilisation

Rehabilitation of Unbound Pavements Using Foamed

Bitumen Stabilisation


What is Foamed Bitumen?

• Hot Bitumen + Water = Foamed Bitumen

• Enables coating of wet materials

• Foam collapses relatively quickly coating predominantly the finer particles of the material.



Expansion Ratio

V1

V2

Maximum Volume After Foaming

Volume After Collapse of Foam

EXPANSION RATIO = V1/V2

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HALF LIFE - TIME

V1

V2

Maximum Foamed Volume

Half of Maximum Foamed Volume

Half life is the time in seconds for the foam to settle to one-half of the maximum volume which it attained.

Transport and Main Roads“Half-life” is defined as being the time by which the foamed bitumen has reduced its maximum achieved volume by 50%, i.e. half the expansion. After a certain time, the foamed bitumen collapses. The half-life is measured in seconds and usually lies between 10 and 15 seconds. As a rule: The larger the expansion and the longer the half-life, the better the quality of the foamed bitumen.

Important for the assessment of the foamed bitumen quality: As the percentage of added water is increased, the parameters “half-life” and “expansion” develop in opposite directions.



Binder Requirements

• Class 170 Bitumen – 3.5%o Equivalent to Pen 80 – 100

o Inclusion of a bitumen foaming agent

• Hydrated Lime – 2%o Superior early strength and

performance


Construction Process

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Tray tests 1

• To check application rate

• Should be done regularly

• Usually 3 trays, each a third of a square metre


Tray tests 2

• Tare scales with trays before laying out trays

• Stop applicator very soon after passing over trays


Lime applied

• Multiple tests in series if necessary

• Reapply lime in trays

• Rate must be correct before allowing the run/s to be completed


Slake Lime 1

• Necessary for quicklime only

• Multiple passes may be necessary to ensure full slaking


Slake Lime 2

• Slaking generates steam clouds

• Environmental and perhaps safety concerns


Slake Lime 3

• Temperature may indicate if hydration is complete

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Foamed bitumen stabilisation 1

• Foamed bitumen stabiliseASAP after slaking is complete


Foamed bitumen stabilisation 2

• Stabiliserpushes bitumen tanker

• Check foaming of bitumen at start of run (halt if necessary)


Compaction

• Follow stabilising run with compaction equipment

• Be aware if padfoot allowed too close to surface its pattern will reflect through to the seal.


Testing

• Sample ASAP after stabilising for tests such as bitumen content

• Sample ASAP after compaction to obtained reference density

• Complete reference density test ASAP (within 2 hours) after stabilising (binders affect compaction).

Transport and Main Roads Transport and Main Roads Pavement Design –Foamed Bitumen

• Performance Criteria??? o Assumed to fatigue and behave similar to asphalt

o Reduce Vb due to low bitumen content

• Resilient Moduluso Based off laboratory test results

o Reduction factors are applied to laboratory test values to account for field moisture conditions, field compaction and material variability

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Capillary Rise Over TimeTransport and Main Roads Capillary Rise of

Various Base Materials


Issue

• In projects where a variation in the pavement materials exist the current test methods do not always give meaningful compaction results. The material sampled to determine MDD may not be the same type of material sampled to determine compaction ratio after the grader and stabiliser have been over it

Bruce Highway @ Pine Rivers

Shoulder widening for new steel cable guardrails

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As designed concept

0.5 to 1.0m wide existing shoulder

embankment

asphalt 100 to 150mm deep

NEW CONSTRUCTION

Note: - new construction was originally designed as unsealed RAP, but unsafe. Therefore asphalt was designed as surfacing.

edge line

New steel wire guardrail

AS DESIGNED SHOULDER AND NEW GUARDRAIL

existing Bruce Highway pavement

Deep lift asphalt

3.0m wide shoulderup to 2 m wide


0.5 to 1.0m wide existing shoulder

AS CONSTRUCTED SHOULDER AND GUARDRAIL

Deep lift asphalt Foamed bitumen stabilised milled gravel and asphalt - 150mm deep

sealed surface

edge line

existing Bruce Highway pavement

New steel wire guardrail

3.0m wide shoulder


Foamed bitumen shoulder in place


Fresh bitumen seal


Bitumen seal over foamed bitumen shoulder


Mixing plant for foamed bitumen milled product

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Lime hopper


Start = load box with screen


Control panel


Controls for mixing foamed bitumen


Pugmill end – to stockpile


Stockpile of recycled material before stabilisation

Transport and Main Roads - aapaqtmr.org · 23-May-12 3 Transport and Main Roads Performance...

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Transcript of Transport and Main Roads - aapaqtmr.org · 23-May-12 3 Transport and Main Roads Performance...