control of early cracking of concrete bridge decks compaction and durability of concrete l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Control of Early Cracking of Concrete Bridge Decks (Compaction and Durability of Concrete) PowerPoint Presentation
Download Presentation
Control of Early Cracking of Concrete Bridge Decks (Compaction and Durability of Concrete)

Loading in 2 Seconds...

play fullscreen
1 / 31

Control of Early Cracking of Concrete Bridge Decks (Compaction and Durability of Concrete) - PowerPoint PPT Presentation


  • 602 Views
  • Uploaded on

29 th September 2005. Control of Early Cracking of Concrete Bridge Decks (Compaction and Durability of Concrete). Presenter: Taha Ahmed, Project Engineer, Bridge Maintenance & Rehabilitation Methods RTA Bridge Technology Section. Australian Small Bridges Conference 2005.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Control of Early Cracking of Concrete Bridge Decks (Compaction and Durability of Concrete)' - Audrey


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
control of early cracking of concrete bridge decks compaction and durability of concrete

29th September 2005

Control of Early Cracking of Concrete Bridge Decks (Compaction and Durability of Concrete)

Presenter: Taha Ahmed, Project Engineer,

Bridge Maintenance & Rehabilitation Methods

RTA Bridge Technology Section

Australian Small Bridges Conference 2005

control of early cracking of concrete bridge decks a case study
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Contents

  • Background
  • Concrete cracking – causes and consequences
  • Early cracking – mitigation strategies
  • Case study – Four Mile Creek Bridge
    • Description of the bridge
    • Construction practices adopted
    • Instrumentation and data logging
    • Data analysis and deck inspections
    • Conclusions
control of early cracking of concrete bridge decks a case study3
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Background

Bridge Over Plain Creek, 22 km NE Dubbo, Golden HWY

control of early cracking of concrete bridge decks a case study4
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Background

Macksville Bridge Over Nambucca River 52.49 km N Kempsey

control of early cracking of concrete bridge decks a case study5
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Background

  • Cracks diminish durability & structural integrity
  • Cracking commences within first few days
  • Visible cracks in concrete decks within first year
  • Early cracking is the single most prevalent problem
  • Many RTA controlled bridges suffer deck cracking
  • 100,000 bridges suffer early deck cracking in USA
  • RTA requires deck waterproofing & surfacing
control of early cracking of concrete bridge decks a case study6
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Concrete Cracking

  • Main causes of cracking
    • Physical changes (temperature and moisture)
    • Structural loadings
    • Chemical reactions
  • Main components of early cracking :
    • Plastic settlement
    • Plastic shrinkage
    • Thermal shrinkage
control of early cracking of concrete bridge decks a case study7
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Early Cracking – Mitigation Strategies

  • Concrete mix design (mix engineer)
    • W/c and cement content/type
    • Aggregate type and size
    • Supplementary cementitious materials
  • Structural design (design engineer)
    • End restraint and support stiffness
    • Deck reinforcement and thickness
    • Bridge articulation
  • Construction practices (contractor/ project manager)
    • Compaction/ finishing/curing
    • Control of rates of heating/cooling & evaporation
control of early cracking of concrete bridge decks a case study8
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Description of the 4 Mile Creek Bridge

control of early cracking of concrete bridge decks a case study9
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Construction Practices - 4Mile Creek Bridge

  • Control concrete placement and compaction
  •  Prior placement and curing of shear keys
  • Attention to construction joints
  • Use of vibrating screed
  • Continuous steel bull floating before broom finish
  • Protection of fresh concrete from evaporation
  • Wet-cure deck by soaker hoses over hessian
  • Apply thermal insulation
    • 60 mm Glasswool Anticon roofing blanket (foil side upward)
    • Two 0.3 mm black polyethylene sheets
control of early cracking of concrete bridge decks a case study10
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Construction Practices - 4Mile Creek Bridge

  • Four Mile Creek Bridge
control of early cracking of concrete bridge decks a case study11
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Instrumentation - 4Mile Creek Bridge

  • Thermocouples
    • 22 k-type wire thermocouples (+/- 1C)
    • 6 locations, top & bottom reo
    • Two locations with temperature profile
  • Strain gauges
    • 12 Vishay EGP-120 wire resistance (+/-10ms)
    • 6 locations, top & bottom reo
  • Dataloggers
    • 2 Series 3 DataTakers
  • Instrumentation box
control of early cracking of concrete bridge decks a case study12
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Instrumentation - 4Mile Creek Bridge

control of early cracking of concrete bridge decks a case study14
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Data Analysis - 4Mile Creek Bridge

  • Temperature monitoring
    • Placement temp. was 11C ( 20/5.5C max/min)
    • RH 77%, no wind speed recorded (calm)
    • Following two days temps were 20/4.5 C &17/8C
    • Average temp over 7 days was 17/6.5C.
    • Max rise in deck temp 11C at 12 hrs
    • Max temp difference in deck 4C at 12 hrs
    • Deck temp almost uniform, 19C at 7 days
    • Max gradient in planks 14C at 12hrs, 6C at 48hrs almost zero at 7 days
slide19

Data Analysis - 4Mile Creek Bridge

  • Strain monitoring
    • Strains recorded at top and bottom reo only
    • Strains were negative, i.e. shrinkage
    • Strains peaked to 150 ms at 24 hrs
    • Successive peaks at noon gradually decreasing
    • Max strain of 80 ms at 7days
    • Strain gradient, top and bottom, 30 ms at 48hrs
    • Strain gradient insignificant at 7 days
slide24

Data Analysis - 4Mile Creek Bridge

  • Crack monitoring
    • No visible cracks at 7 days
    • No visible cracks at “28” days
    • Link slab cracks of 0.12 mm at 4 months
    • <0.025 cracks in deck outside link slabs
control of early cracking of concrete bridge decks a case study29
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Crack monitoring – 4 Months

Crazing in Span 1 < 0.025 mm

Longitudinal crack 0.05 – 0.075 mm in Span1-Span2 Infill

Longitudinal Crack 0.025 mm in Span1

control of early cracking of concrete bridge decks a case study30
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Crack monitoring – 4 Months

Longitudinal Crack 0.05 – 0.075 mm in Span2-Span3 Infill

Longitudinal Crack <0.025 mm in Span 2

Longitudinal Crack 0.1 – 0.12 mm in Span2 –Span 3 Infill

control of early cracking of concrete bridge decks a case study31
Control of Early Cracking of Concrete Bridge Decks - A Case Study

Conclusions

  • Bridge Technology’s construction practices adopted have alleviated early deck cracking.
  • Further refinement of construction practices is required especially the way link slabs are constructed.
  • Further refinement of bridge design is required