crack and seat presentation.pdf
TRANSCRIPT
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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