Progress Report on OHare Modernization Plan

1
Progress Report on OHare Modernization
Plan
Concrete Mix Designs
University of Illinois Department of Civil and
Environmental Engineering
February 8, 2004
2
Concrete Mix Design Team

• Prof. David Lange
• Concrete materials / volume stability
• High performance concrete
• Prof. Jeff Roesler
• Concrete pavement design issues
• Concrete materials and testing

3
Graduate Research Assistants

• Cristian Gaedicke
• Concrete mix design / fracture testing
• Sal Villalobos
• Concrete mix design and saw-cut timing
• Rob Rodden
• testing, instrumentation, shrinkage
• Zach Grasley
• Concrete volume stability

4
Overview of Project Objectives

• Mix Design
• Minimize cracking potential
• Short and long-term
• Minimize Shrinkage
• Joint Enhancement
• Aggregate Interlock
• Targeted dowel placement

5
Completed Activities

• Survey of Existing Concrete Mixes
• Initial Mix and Testing Methods Evaluation
• Technote Shrinkage Reducing Admixtures in
  Concrete Pavements
• Technote Fiber-Reinforced Concrete Pavements

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Survey of Existing Mixes
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Survey of Existing Mixes
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Initial Mix Evaluation

• Mix used in previous projects at OHare
• Revised Mix 1905 (2000)

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Common Strength Tests
Compressive strength and Concrete elastic modulus
3rd Point Loading (MOR)
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Standard Concrete Shrinkage
Concrete shrinkage prism ASTM C157
Mortar Bar shrinkage ASTM C596
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Initial Mix Evaluation

• Compressive strength ? 4470 psi _at_ 7days
• Modulus of Rupture ? 380 psi _at_ 7days
• Drying shrinkage ? 440 mm
• Autogenous shinkage ?170 mm
• Instrumented cube (measurement of RH and Temp.)

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Fracture vs. Strength Properties
MOR
GF

• Peak flexural strength (MOR) same but fracture
  energy (GF) is different
• Avoid brittle mixes

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Fracture Test Setup
Notched Beam Test
Wedge Split Test
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Wedge Split Test Result

• The concept of GF
• Wedge split Gf and lch EGf/ft2

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Effect of Aggregate Type on GF
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Benefits of SRA in Pavements

• Reduced Shrinkage and Cracking Potential
• Near 50 60 reduction
• Increased Joint spacing

Brooks et al. (2000)
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Problems of SRA in Pavements

• Technical
• Early age strength loss
• Delay in set time
• Interaction with air entrainment admixture
• Potentially washout with water
• Economic
• Cost

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Fiber-Reinforced Concrete Pavements

• Application of low volume, structural fibers

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Benefits of FRC Pavements

• Increased flexural capacity and toughness
• Thinner slabs
• Increased slab sizes
• Limited impact on construction productivity
• Limits crack width
• Promotes load transfer across cracks (?)

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Use of FRC in Pavements

• Fiber-reinforced concrete

• Final cost reduction of 6 to an increase of
  11

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Testing Program

• Variables- Phase I

• Proposed Variables- Phase II

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Testing Factorial

• Where
• fc7 compressive strength at 7 days
• E 7 modulus of elasticity at 7 days
• Gf 7 energy release rate at 7 days
• sfl 7 flexural strength at 7 days
• ssp 7 splitting strength at 7 days
• esh drying shrinkage
• eas autogenous shrinkage

• 28-day properties
• Fracture Energy

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Joint Type Selection

• Are dowels necessary at every contraction joint?

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Aggregate Interlock Joint

• Dummy contraction joint
• No man-made load transfer devices
• Shear transfer through aggregate/concrete surface
  
• aggregate type and size joint opening

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Joint Design

• Saw-cut timing
• Aggregate
• Interlock
• Targeted
• Dowels

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Joint Design

• Promote high shear stiffness at joint
• High LTE
• Larger and stronger aggregates
• Increase cyclic loading performance
• Predict crack or joint width accurately

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Effect of Concrete Mix on GF
38mm Trap Rock
38 mm Gravel
25mm Trap Rock
25mm Gravel
25mm Gravel
25mm Limestone
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• GF and Shear Load Transfer

• Shear load transfer depends on GF at 28 days.
• Concrete with high GF at 28 days provides good
  shear load transfer across cracks/joints.

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• AGGREGATE TYPE
  
• 
  

TRAP ROCK
gt RIVER GRAVEL

gt LIMESTONE
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• AGGREGATE GRADATION
• 
  

Gradation doesnt have much impact.
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• AGGREGATE SIZE

LARGE BETTER THAN SMALL
(38MM)
(25MM)
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Other significance of GF

• GF better characterize the effect of CA on
  concrete performance.
• w/c 0.49
• ? fc (12 hrs) 3.80 4.20 MPa
• ? fc (28 days) 31.7 38.1 MPa
• ? GF (12 hrs) 52.7 194.5 N/m
• ? GF (28 days) 93.7 573.3 N/m

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Saw-cut Timing and Depth

• Notch depth (a) depends on stress, strength, and
  slab thickness (d)
• Stress f(coarse aggregate,?T, RH)

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Requirements for Saw-cut Timing
Stress
Strength
s
Time

• Stress f(thermal/moisture gradients, slab
  geometry, friction)
• Strength (MOR,E) and fracture parameters (Gf or
  KIC) with time

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Project Goals

• Crack-free concrete (Random)
• Specification for shrinkage
• Specification for GF
• Specifiction for MOR
• Optimal joint type
• Aggregate Specification
• Stabilized base
• Saw-cut timing
• Cost effective!
• Minimum Quantity of Cement
• Improvement of Aggregate Interlock

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Concrete Mix Design

• Minimum strength criteria (MORmin)
• Minimum fracture energy (GF)
• Max. concrete shrinkage criteria (?sh)
• Aggregate top size (Dmax)
• Strong coarse aggregate (LA Abrasionmax)
• Saw-cut timing table
• Slow down hydration rates and temperature

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Summary of Progress

• Concrete Mix Survey Technote
• FRC Technote
• SRA Technote
• Initial Mix Evaluation
• Phase I - Testing Program
• Saw-Cut Timing

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• Questions