Concrete%20(PCC)%20Mixture%20Designs%20for%20O

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Concrete (PCC) Mixture Designs for OHare
Modernization Program
Principal Investigators Prof. Jeff Roesler Prof.
David Lange
PROJECT GOAL Investigate cost-effective concrete
properties and pavement design features required
to achieve long-term rigid pavement performance
at Chicago OHare International.
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Acknowledgements

• Principal Investigators
• Prof. Jeff Roesler
• Prof. David Lange
• Research Students
• Cristian Gaedicke
• Sal Villalobos
• Rob Rodden
• Zach Grasley
• Others students
• Hector Figueroa
• Victor Cervantes

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Project Objectives

• Develop concrete material constituents and
  proportions for airfield concrete mixes
• Strength
• volume stability
• fracture properties
• Develop / improve models to predict concrete
  material behavior
• Crack width and shrinkage
• Evaluate material properties and structural
  design interactions
• joint type joint spacing (curling and load
  transfer)
• Saw-cut timing

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Project Objectives
Material constituents and mix design
Analysis of existing concrete mix designs
Long-term perfor-mance at ORD
Concrete properties
Laboratory tests
Modeling
Test for material properties
Optimal joint types and spacing.
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FY2005-06 Accomplishments

• Tech Notes (TN) -
• TN2 PCC Mix Design
• TN3 Fiber Reinforced Concrete for Airfield Rigid
  Pavements
• TN4 Feasibility of Shrinkage Reducing Admixtures
  for Concrete Runway Pavements
• TN11 Measurement of Water Content in Fresh
  Concrete Using the Microwave Method
• TN12 Guiding Principles for the Optimization of
  the OMP PCC Mix Design
• TN15 Evaluation, testing and comparison between
  crushed manufactured sand and natural sand
• TN16 Concrete Mix Design Specification
  Evaluation
• TN17 PCC Mix Design Phase 1

www.cee.uiuc.edu/research/ceat
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FY2006 Accomplishments

• Tech Notes (TN) -
• TN21 An Overview of Ultra-Thin Whitetopping
  Technology
• TN23 TN23 Effect of Large Maximum Size Coarse
  Aggregate on Strength, Fracture and Shrinkage
  Properties of Concrete
• TNXX Effects of Concrete Materials and Geometry
  on Slab Curling
• TNYY Concrete Saw-Cut Timing Model
• TNZZ Functionally Layered Concrete Pavements

www.cee.uiuc.edu/research/ceat
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Presentation Overview

• Large-sized coarse aggregate mixtures
• Saw-cut timing model
• Slab Curling
• Field Demo Project
• Recycled Concrete Aggregate

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Aggregate Interlock Joints

• Reduced LTE with small maximum size CA

Dowels deemed necessary
Crack width, cw
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Larger maximum size CA
Aggregate Interlock Joints
Larger aggregate top size increases aggregate
interlock and improves load transfer
Crack width, cw
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Why Larger Size Coarse Aggregate?

• Potential benefits
• Less paste ? lower cementitious content
• Shrinkage
• Higher toughness
• Fracture and crack propagation resistance
• Increase roughness of joint surfaces
• Increased load transfer between slabs
• Reduced of dowels
• Durability (??)
• D-cracking

• Cost - Effectiveness

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Experimental Design

• Effect of aggregate size (1.0 vs. 1.5)
• Effect of 1.5 coarse aggregate
• Total cementitious content
• 688 lb/yd3, 571 lb/yd3, 555 lb/yd3 and 535 lb/yd3
  
• Water / cementitious ratio
• 0.38 versus 0.44
• Fly Ash / cementitious ratio
• 14.5 versus 0
• Effect of coarse aggregate cleanliness

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Mix Design Results
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Phase II Mix Summary
Effect of larger-size coarse aggregate on
strength
Larger-size coarse aggregate
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Drying Shrinkage Phase II
Effect of larger-size coarse aggregate on
shrinkage
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Fracture Energy Results-Phase II
Effect of larger-size coarse aggregate on
fracture properties

• Age 28-days

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PCC Mix Design Phase II

• Summary
• Larger aggregates reduce strength by 20, but
• 28-day GF similar ? similar cracking resistance
• Larger aggregates reduce concrete brittleness
• 1-day fracture energy ? with larger MSA
• ? greater joint stiffness / performance
• No significant shrinkage difference
• TN23 April 2006

Roesler, J., Gaedicke, C., Lange, Villalobos,
S., Rodden, R., and Grasley, Z. (2006),
Mechanical Properties of Concrete Pavement
Mixtures with Larger Size Coarse Aggregate,
accepted for publication in ASCE 2006 Airfield
and Highway Pavement Conference, Atlanta, GA.
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Saw-Cut Timing Model

• Concrete E and fracture properties(cf ,KIC) at
  early ages.
• Develop curves of nominal strength vs notch depth
  for timing.

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

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Saw-Cut Timing and Depth

• Saw cut depth / timing EXPERIENCE
• Fracture properties at early ages
• Critical Stress Intensity Factor (KIC)
• Critical Crack Tip Opening Displacement (CTOCC)
  form this type of specimen
• Wedge Splitting Test (WST)
• need geometric factors

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Saw-Cut Timing and Depth

• Objectives
• Develop a FEM Model for WST specimens
• Integrate measured fracture properties with a
  Size Effect Model
• (after Zollinger et al. 2001)
• Effect of coarse aggregate size, cementitious
  content and age on timing/depth
• Determine saw cut depth for different pavement
  thicknesses

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Saw-Cut Timing and Depth

• Process

• Concrete Mix
• Aggregate size
• Cementitious content

Crack Propagates
FRACTURE PROPERTIES
Wedge Split Test
FEM Model
Saw Cut Depth Model
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Wedge Split Testing

• WST setup and specimen

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Saw-Cut Timing and Depth

• FEM Model
• Special Mesh around crack tip
• Q8 elements
• Symmetry and BC considerations

200 mm
100 mm
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Saw-cut timing and depth

• FEM Model Results
• Determination of Fracture parameters

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Saw-cut timing and depth

• FEM Model Results
• Determination of Fracture parameters

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Saw-Cut Depth Model

• SEM Model (Bazant)

Nominal Strength vs Notch Depth Chart
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Saw-cut timing and depth

• Mix proportions
• Aggregate gradations

• Concrete

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Concrete Fracture Properties

• Critical Stress Intensity Factor (KIC)
• Critical Crack Extension (cf)

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Curling Stress in Concrete Slab

• Westergaard Slab Curling

Saw cut Depth
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Low Cementitious Content

• Saw Cut Depth Charts

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High Cementitious Content

• Saw Cut Depth Charts

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Summary of Notch Depth Requirements
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Saw-cut timing and depth

• Summary
• Saw cut depth increases with concrete age
• dramatic increase in depth after 10 to 12 hr.
• Larger maximum aggregate size increases saw cut
  depth
• High cementitious materials especially

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Curling Questions

• How does shrinkage effect slab size?
• What are the combined effect of
  moisture/temperature profile?
• What is the role concrete creep?
• How do other concrete materials behave FRC
  SRA?

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Slab Curling

• Effects of materials and slab geometry on
  moisture and temperature curling

after Grasley (2006) Rodden (2006)
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Field vs Lab
Field
Lab
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RH Profile - Lab
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STD Cube Moisture Stresses
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Summary of Curling

• Moisture profile effects
• Temperature
• Set temperature
• Shrinkage Reducing Admixtures
• Fiber Reinforced Concrete

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Joint Type Analysis

• How can we choose dowel vs. aggregate interlock
  joint type joint spacing?
• Need to predict crack width LTE
• Shrinkage, zero-stress temperature, creep
• Aggregate size and type (GF)
• Slab length base friction

If we use aggregate interlock joints there is a
significant cost savings
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Field Demo Project
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Joint Opening Measurement
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Two week joint opening
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Concrete Free Shrinkage
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Dong/Zach formula
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Slab Lift-Off (Curling)
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Crack Width Model Approach
after Zollinger
Crack spacing Drying shrinkage Temperature
drop Restraints
Base friction Curling (thermal and
moisture) Steel reinforcement
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Recycled concrete aggregate (RCA)
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RCA
Can RCA (coarse) provide similar mechanical
properties for airfield rigid pavements as virgin
aggregates?

• Slight strength reduction
• Higher shrinkage potential
• Lower modulus
• Lower concrete density
• Potential cost saving

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Use of RCA for OMP

• RCA may lead to cost savings
• Disposal, trucking, aggregate costs
• RCA may increase shrinkage?
• RCA less stiff than natural aggregate
• RCA can shrink more than natural aggregate
• Shrinkage may be same or reduced if RCA is
  presoaked to provide internal curing

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UIUC First Trial

• RCA from Champaign recycling plant
• Concrete came from pavements, parking garages,
  etc.
• Mix of materials with unknown properties
• Material washed, dried, and sieved to match
  natural fine aggregate
• Soaked for 24 hrs, surface dried, and then 100
  replacement of natural fine aggregate

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Saturated RCA vs Lab Aggregates

• Similar autogenous shrinkage curves

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Mechanical Property Test Plan

• Simple lab crusher
• Three Point Bend (TPB) test
• Fracture properties
• (Spring 2006)
• Full-scale crushing at contractor
• Fracture / strength properties
• Shrinkage
• (Summer 2006)

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Sample Preparation

• 1. Crush Process

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Sample Preparation (Cont)

• 2. Gradation

• 3. Mixture Design

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Sample Preparation (Cont)
4. Dimensions
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Sample Preparation(Cont)

• 3 beams
• Tested 7 day
• Position control displacement
• CMOD 3 Max
• 3 Cycles
• Load CMOD curve

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Test
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Plain Concrete Fracture Behavior
PCC
RCA
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FRC Fracture Behavior
FRC
RCA w/ Fibers
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Fracture Energy
 
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Results (Cont)
Virgin
RCA
Virgin
RCA
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Results
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RCA vs FRCA
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Summary of Fracture Properties
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Fracture Energy
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Initial Findings

• RCA reduce the concrete fracture energy by 50
• RCA does not affect the fracture energy in fiber
  reinforced concrete (peak load still less)

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Summer 2006 RCA Concrete Mixtures
Type of Coarse Aggregate Virgin (V) Virgin (V) Recycled (R) Recycled (R) V R
Fibers Yes No Yes No No
Mix ID VF VP RF RP MP
Mix date 7.11.06 7.11.06 7.21.06 7.21.06 7.24.06
Mixture lb/yd3 lb/yd3 lb/yd3 lb/yd3 lb/yd3
Water 308 308 308 308 308
Cement Type I 607 607 607 607 607
Coarse Aggregate 1645 1645 1645 1645 1645
Fine Aggregate 1360 1360 1360 1360 1360
Synthetic Fibers 3 --- 3 --- ---
BSGSSD 2.42 AC 5.7
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RCA Tests

• Fresh properteis
• Slump, Density, Air
• Compressive Strength (7 days)
• Split Tensile (7 days)
• Three Point Bending at 7days
• GF
• Gf
• CTODc
• Drying Shrinkage 28 days

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RCA Summary to Date

• Optimization of RCA gradation may lead to
  reduction in overall shrinkage
• Other concerns
• Reduced concrete strength and modulus
• Potential for ASR from RCA?
• Source of chlorides to cause corrosion of dowels?
• Future work - use RCA with known properties
• Try different gradations
• Measure strength/fracture properties also

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Work remaining for FY2006

• Joint type and size analysis cont
• Saw-cut timing model - TN
• Materials and geometry effects on curling - TN
• Functionally-layered concrete pavements - TN
• Recycled concrete aggregate cont

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QUESTIONS

• www.cee.uiuc.edu\research\ceat
• Thanks!