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1616thth Road Pavement ForumRoad Pavement Forum

CSIR Conference CentreCSIR Conference Centre

1111 12 November 200812 November 2008

CONCRETE PAVEMENTCONCRETE PAVEMENT

REHABILITATIONREHABILITATION

Philip Joubert

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Presentation Overview

Look at:

Restoration of pavement lifein

existing rigid pavementusing techniques

of

Cracking & Seatingor

Rubblizing

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Rehab. of Concrete Pavement

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Typical Failed Pavements

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Typical Failed Pavements

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Typical Failed Pavements

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Typical Decision Flow DiagramTypical Decision Flow Diagram

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1. CRACK AND SEAT (C&S)1. CRACK AND SEAT (C&S)

Principles and MethodPrinciples and Method

ofof

Crack and SeatCrack and Seat

OperationsOperations

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Principle of Cracking & SeatingPrinciple of Cracking & Seating

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Objective of C & S

TO:

modify characteristics of rigid pavement:

into a more flexible structure,

BUT ALSO TO:

minimise asphalt overlay thickness :

by retaining max pavement stiffness / strength

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C & S Technique - 1

Produces shorter slabs

0.6 2m in length

Retains structural integrity

Induces fine, vertical, transverse cracks in JCP

Reduces effective length of slab between joints.

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C & S Technique - 2 Size of slabs is effectively reduced

Therefore: Horizontal strains - from thermal movements:

distributed more evenly over pavement,

less likely to cause reflective cracks in HMA overlay

Cracks induced in PCC slab so fine that:

load transfer between newly formed slabs = good

because of aggregate interlock.

After cracking:

PCC segments firmly seated by heavy pneumatic tire roller

ensure - no voids beneath PCC segments prior to overlay

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Typical Equipment

8600 Badger Guillotine Breaker 20 ton Pneumatic Tyre Roller

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Cracking & Seating Operation

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Typical Induced Crack

Broken core showing good

aggregate interlocking

Crack should be verticalthroughout depth of core

Core taken from a

450mm thick

pavement

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C & S @ Heathrow Airport

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C & S @ Heathrow Airport

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C & S Issues affecting performanceC & S Issues affecting performance

Foundation = firm with good seating

Too small slab size: accelerate cracking

Better in un-reinforced JCP

Method preferred for cracked/faulted

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2.2. RubblizationRubblization ((Asphalt Institute)

Process of: breaking / pulverising PCC pavement in-place

into small, interconnected pieces (75 - 200mm)

Serve as base course for HMA overlay.

Deflections / weak spots: filled with coarse aggregate

Rubblized - compact with steel roller The rubblizing process:

reduces slab to an granular base for overlay

eliminates all reflective cracking concerns

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Distressed Concrete

Mid-panel cracking

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Water trapped below concrete

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Before rubblization

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After rubblization

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RubblizationRubblization MethodMethodTo meet specifications for concrete pavements:

1. Firstly - break using guillotine

2. Then - 16hammer Breaker

3. Then - grid roller:

to further pulverize

to shape concrete particles at surface

to begin compaction process.

4. Final - seating typically accomplished with:

20-ton pneumatic-rubber tyre roller [PTR]

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Layer StiffnessLayer Stiffness

The rubblized layer stiffness:

700 - 3000MPa

Compared a typical high quality crushed

aggregate base 500 MPa

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Pre-cracking 500mm concrete

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Pre-cracking pattern

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Pre-cracking concrete

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Rubblization

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Completing the rubblization

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Completing the rubblization

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Surface after grid rolling

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Surface after grid rolling

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Test hole

T t h l

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Test hole

T t h l

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Test hole

P i ith M/T V hi l

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Paving with M/T Vehicle

Pl i t b l

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Placing aggregate base layer

C t l i

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Concrete overlay in process

S t i bilitS t i bilit

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SustainabilitySustainability

No hauling or disposal costsNo hauling or disposal costs

Existing pavement retainedExisting pavement retained -- saves natural resourcessaves natural resources

Saves landfill spaceSaves landfill space

Expedites constructionExpedites construction

Environmentally friendlyEnvironmentally friendly

CostCost--effective as rehabilitation technique.effective as rehabilitation technique.

Existing concrete pavement stays in placeExisting concrete pavement stays in place

Becomes base for new HMA pavementBecomes base for new HMA pavement

Reduce or eliminate need for new virgin aggregates.Reduce or eliminate need for new virgin aggregates.

Weather delays minimisedWeather delays minimised -- sub grade never openedsub grade never opened

Th k YTh k YG i H ?Going Home?

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Thank YouThank YouGoing Home?Going Home?

Project sizeProject size

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Project sizeProject size

Minimum: 25 000mMinimum: 25 000m2

R30/m2 2 weeks on site