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Progress Report on Concrete Mix Designs for O’Hare Modernization Plan. University of Illinois Department of Civil and Environmental Engineering . July 14, 2005. Project Goal.

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Progress Report on Concrete Mix Designs for

O’Hare Modernization Plan

University of Illinois

Department of Civil and Environmental Engineering

July 14, 2005


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Project Goal

Investigate cost-effective concrete properties and pavement design features required to achieve long-term pavement performance at Chicago O’Hare International.


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Project Objectives

  • Develop material constituents and proportions

  • Characterize strength, volume stability,and fracture properties of airfield concrete mixes

  • Develop / improve models to predict material behavior.

  • Evaluate material properties and structural design interactions, e.g.,

    • joint spacing

    • joint types

    • 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

Laboratory tests

Concrete properties

Modeling

Test for material properties

Optimal joint types and spacing.


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2005 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




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Tech Note 3

  • Fiber Reinforced Concrete for Airfield Rigid Pavements

  • Final cost: reduction of 6% to an increase of 11%


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Tech Note 4

  • Feasibility of Shrinkage Reducing Admixtures for Concrete Runway Pavements

    • Reduced Shrinkage and Cracking Potential ~ 50% reduction

    • Cost limitations (?)

Figure 1. Unrestrained shrinkage of mortar bars, w/c = 0.5 (Brooks et al. 2000)


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Tech Note 11

  • Measurement of Water Content in Fresh Concrete Using the Microwave Method

    • Strengths: quick, simple, and inexpensive

    • Limitations: need accurate information on

      • cement content

      • aggregate moisture and absorption capacity


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TN 12: Guiding Principles for the Optimization of the OMP PCC Mix Design

  • 1st order:

    • Strength, workability

  • 2nd Order:

    • Shrinkage, fracture properties

    • LTE & strength gain


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Tech Note 15 PCC Mix Design

  • Evaluation, testing and comparison between crushed manufactured sand and natural sand

    • Gradation

    • physical properties


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Manufactured vs Natural Sand PCC Mix Design

4mm

500mm

4mm

500mm

  • Visual evaluation

    • Material retained in the #8 sieve shows difference in the particle shape

    • The Manufactured sand shows a rough surface and sharp edges due to the crushing action to which it was subjected.

Sieve No. 8

Sieve No. 50


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Tech Note 16 PCC Mix Design

  • Concrete Mix Design Specification Evaluation

    • Preliminary P-501 evaluation

    • Strength, shrinkage, and material constituent contents


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2005 Accomplishments PCC Mix Design

  • Specification Assistance

    • On-site meetings at OMP headquarters

    • Continued specification recommendations:

      • Material constituents (aggregate type and size, SCM, etc.)

      • Modulus of rupture and fracture properties of concrete

      • Shrinkage (cement content, w/c ratio limits,etc.)

      • Saw-cut timing, spacing and depth

      • Pavement design


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TN17: PCC Mix Design Phase 1 PCC Mix Design

  • Develop mix design factorial and verify fresh and hardened concrete properties

  • More later …


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Project Tasks and Progress PCC Mix Design

Status

Done,

TN2, 3, 4, 15

  • Literature Review

    • Survey of existing mix designs

    • Review of mix design strategies

  • Volume Stability Tests

    • Drying and Autogenous shrinkage

    • Optimization of concrete mixes to reduce volumetric changes

  • Strength Testing

    • Modulus of rupture, splitting and compressive strength

    • Fracture energy and fracture surface roughness

Done, TN 12

In progress,

TN 12 and TN 17.

In progress, TN 12 and TN 17

Start tests in July


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Project Tasks and Progress PCC Mix Design

  • Joint Type Design

    • Slab size and jointing plans: productivity, cost, performance.

    • Optimization of concrete aggregate interlock to ensure shear transfer.

    • Joint (crack) width prediction model for concrete materials.

In progress, TN 3. Requires fracture results.

In progress, TN 12. Fracture tests

In progress, need shrinkage/creep results.


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Project Tasks and Progress PCC Mix Design

Review in progress, requires fracture results.

  • Saw-cut timing and depth

    • Saw-cut timing criteria for the expected materials

    • Analytical model / Validation

  • Fiber Reinforced Concrete Materials

    • Overview of structural fibers for rigid pavement

Literature Review done, TN 3.


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PCC Mix Optimization – Phase I PCC Mix Design

  • Factor Levels

    • Three variables changed independently:

      • Coarse aggregate top size

        • ¾” and 1.5” top sizes

      • Total cementitious content

        • 588lb/yd3 versus 688lb/yd3

      • Water / cementitious ratios

        • 0.38 versus 0.44

    • Phase I was used to develop Phase II mixes.


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PCC Mix Optimization – Phase I PCC Mix Design

  • Mix Design

    • Five mixes proposed to investigate 3 variables:

    • Water reducer was added as necessary


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PCC Mix Optimization – Phase I PCC Mix Design

  • Results

    • Values within range for a typical O’Hare mix


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PCC Mix Optimization – Phase II PCC Mix Design

  • Phase II mix objectives:

    • Mechanical Properties

      • Meet specified strength, air content, workability, etc

      • Maximize fracture resistance & ductility

  • Volume Stability

    • Minimize shrinkage

  • Load Transfer

    • Maximize aggregate interlock


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    PCC Mix Optimization – Phase II PCC Mix Design

    • Experimental Design

      • Primary factors of interest:

        • Max. aggregate size, w/c ratio, cement content and

          fly ash /cementitious ratio.

      • No water reducers are added in Phase II


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    PCC Mix Optimization – Phase II PCC Mix Design

    • Mix Design

      • Mixes identical to Phase I with the addition of two mixes to investigate O’Hare specification extremes

      • No water reducers are added in Phase II


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    PCC Mix Optimization – Phase II PCC Mix Design

    • Testing

      • Fresh concrete properties

        • Slump, Air Content, Unit Weight

    • Mechanical Testing

      • Compressive strength at 7 and 28 days

      • Modulus of Elasticity at 7 and 28 days

      • Split tensile strength at 7 and 28 days

      • Modulus of Rupture at 7 and 28 days

    • Stability Testing

      • Drying and Autogenous Shrinkage trends for 28+ days

    • Fracture tests

      • Early-ages (<48 hrs)

      • Mature age (28 days)


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    PCC Mix Optimization PCC Mix Design

    • Preliminary Strength Summary


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    Toward a shrinkage specification PCC Mix Design

    • How much shrinkage is acceptable?

      • Little information in the literature

      • State of California Materials and Research Lab

        • ASTM C157-64 used

        • Three classes defined

          • Class A: <320 microstrain

          • Class B: <480 microstrain

          • Class C: <640

      • Shrinkage over 735 microstrain is considered very severe


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    Toward a shrinkage specification PCC Mix Design

    • Other recommendations

    Non standard test:

    8x8x2” specimens

    Sealed 2 d, air dried 26 d, soaked 4 d, initial measurement taken, oven dried at 122 F and 17% RH

    Building research station (UK), “Shrinkage of natural aggregates in concrete”, Build. Res. Stat. dig., no. 35, 1963.


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    Toward a shrinkage specification PCC Mix Design

    • Do we know exactly how much shrinkage is acceptable?

      • Not exactly

        • We know when a material is really bad and when a material is really good

      • Bad materials should be avoided, and strategies should be examined for approaching low shrinkage concrete at minimal cost


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    PCC Mix Optimization – Phase II PCC Mix Design

    • Shrinkage Results

      • All mixes show similar drying shrinkage

      • As expected, mixes 688.44 and 688.38 that have a higher amount of cementitious material (688 lb) show higher shrinkage compared to mix 588.38 (588lb of cementitious material)

    • The water cemen-titious ratio is not a significant factor so far.


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    PCC Mix Optimization – Phase II PCC Mix Design

    • Shrinkage Results

      • All mixes show similar drying shrinkage

      • As expected, mixes 688.44 and 688.38 that have a higher amount of cementitious material (688 lb) show higher shrinkage compared to mix 588.38 (588lb of cementitious material).

    • The w/c ratio is not

      a significant factor

      so far.


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    PCC Mix Optimization – Phase II PCC Mix Design

    • Shrinkage models vs. experimental results

      • ACI Model

        • Cement content

        • Fine/Total agg.

        • Entrapped air

        • Volume/Surface

        • Relative humidity

      • This model underestimates the experimental results during the first 28 days for the mixes done so far.


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    PCC Mix Optimization – Phase II PCC Mix Design

    • Shrinkage models vs. experimental results

      • FIB 2000 Model

        • fc at 28 days

        • Volume/Surface

        • Relative humidity

        • Type of cement

      • This model fits the experimental results during the first 28 days for the mixes done so far.


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    Concrete Shrinkage Summary PCC Mix Design

    - 1.5” max aggregate size

    *units in microstrain


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    Fracture Properties PCC Mix Design

    • The relationship between Fracture Energy and Joint Performance

      • Fracture Energy is characterized using GF

      • The Shear Stiffness is a good indicator of Joint Performance


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    Fracture Properties PCC Mix Design

    • Wedge Splitting Test

      • Test configuration

        • Low self weight effect

        • Ideal for early age testing

        • Similar to beam test

      • Load vs. CMOD curve


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    Fracture Properties PCC Mix Design

    ft

    GF = Area under the Curve

    Cracking Area

    • Obtaining the Fracture Energy

      • Calculation of area under the curve


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    Fracture Properties PCC Mix Design

    • Effect of aggregate size on Fracture Energy

      • Larger coarse aggregate and higher Crushing Value increase Fracture Energy


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    Fracture Properties PCC Mix Design

    • Effect of Aggregate Type on GF


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    Fracture Properties PCC Mix Design

    • Other significance of GF

      • GF better characterize the effect of coarse aggregate on concrete performance.

      • For w/c = 0.49

        • f’c (12 hrs) = 3.80 – 4.20 MPa

        • f’c (28 days) = 31.7 – 38.1 MPa

        • GF (12 hrs) = 52.7 – 194.5 N/m

        • GF (28 days) = 93.7– 573.3N/m


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    Requirements for Saw-cut Timing PCC Mix Design

    Stress

    Strength

    s

    • Stress = f(thermal/moisture gradients, slab geometry, friction)

    • Strength (MOR,E) and fracture parameters (Gf / KIC cf / CTODc) with time

    Time


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    Saw-cut Timing and Depth PCC Mix Design

    a

    d

    • Notch depth (a) depends on stress, strength, and slab thickness (d)

    • Stress = f(coarse aggregate,T, RH)


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    Tasks for FY 2006 PCC Mix Design

    • PCC Mix Optimization

      • Fracture testing (finish Fall 2005)

      • Alternative cementitious materials/admix. (Phase III)

        • FRC, HVFA, Slag

        • Manufactured Sand (?)

    • Design and Construction Issues

      • Saw-cut timing (Dec. 2005)

      • Joint (crack) width prediction (Summer 2006)

      • Slab curling analysis* (Summer 2006)


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    Proposed New Ideas PCC Mix Design

    • Two-layer concrete pavements

      • Multi-functional rigid pavement

      • Cost saving

    • GREEN-CRETE

      • Recycled concrete aggregate

      • Effect of recycled aggregate on mechanical and volumetric properties of concrete

    • Experimental pavement section and pavement instrumentation


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    Multi-layer concrete pavements PCC Mix Design

    Porous Concrete Friction/Noise Layer

    h1, E1, υ1, α1, k1, ρ1, D1

    No fibers

    h2, E2, υ2, α2, k2, ρ2, D2

    fB = 0.1%

    Shrinkage Resistant Layer

    h3, E3, υ3, α3, k3, ρ3, D3

    fA = 0.25%

    Fatigue Resistant Layers

    h4, E4, υ4, α4, k4, ρ4, D4

    fA = 0.5%

    Support Layers

    T, RH

    P

    Functions

    Wear Resistant

    h

    E(z), υ(z), α(z), k(z), ρ(z), D(z)

    Shrinkage Resistant

    Fatigue Resistant

    z

    Support Layers

    • Multi-functional rigid pavement:

      • Volume stability and fracture resistance maximized independently

      • Skid resistance, aggregate interlock

      • Reduced slab curling


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    Preliminary Testing of PCC Mix DesignTwo-layer Concrete

    P

    d

    Mixture 1

    h1

    CMOD

    Mixture 2

    h2

    a0



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    Recycled Concrete Aggregate PCC Mix Design

    • Advantages of RCA

      • Performance

        • Improves strength of base when used in base layer

        • Potential to minimize D-cracking and ASR

      • Economic

        • Limited haul distance

        • Reduced disposal costs

        • Lower aggregate cost = lower concrete cost

        • Overall project savings

      • Resource Conservation (RCAC is a green material)

        • Reduced land disposal and dumping

        • Conservation of virgin aggregates

        • Reduced impact to landscapes

    G. P. Gonzalez, H. K. Moo-Young, “Transportation Applications Of Recycled Concrete Aggregate”, FHWA State of the Practice National Review September 2004.


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    Recycled Concrete Aggregate PCC Mix Design

    • Some potential disadvantages

      • Reduced strength and modulus

        • Particularly with a large amount of recycled fines

      • Higher drying shrinkage

        • The reduced stiffness of aggregates reduces the restraint to paste shrinkage

        • Part of the RCA is just hydrated paste… this will also shrink when dried


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    Recycled Concrete Aggregate PCC Mix Design

    • Can we mitigate the disadvantages?

      • Use low w/cm concrete (below ~0.35)

        • Drying shrinkage will be greatly reduced due to decrease in diffusivity

        • Strength and stiffness will be satisfactory

      • But what about autogenous shrinkage in low w/cm?

        • There is evidence that RCA can be used as an “internal curing agent” by saturating the aggregate prior to use


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    Recycled Concrete Aggregate PCC Mix Design

    • Some findings from literature

      • When used with a very low w/cm, RCAC compressive strength can exceed 9000psi at 28 d

      • Autogenous shrinkage can be lowered by 60% by adding saturated RCA

    While there are no reports in the literature, it is likely that RCA increases tensile creep, which would reduce propensity for shrinkage cracking or curling

    I. Maruyama, R. Sato, “A trial of reducing autogenous shrinkage by recycled aggregate”, in Proceedings of self-desiccation and its importance in concrete technology, Gaithersburg, MD, June 2005.


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    Experimental Pavement PCC Mix DesignSections & Instrumentation

    16 instrumented slabs

    80 ft

    75 ft

    34

    400 ft

    • Opportunity to test new ideas!!

    • Factor Levels

      • FRC vs. Plain

      • Slab Size and Curling

      • Joint Type - Dowel vs. no dowels

      • Base Type

    • Gaging

      • RH and Temperature profile

      • Strain

      • Deflection

      • Joint opening

    DIA Project


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    FULL-SCALE TESTING PCC Mix Design

    (Advanced Transportation Loading ASsembly)

    • 80,000 lbs max load

    • 85 feet loading length

    • 65 feet at 10mph

    • Uni- or Bi-directional

    • Variable lateral position

    Test ideas at UIUC


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    Use of Manufactured Sand PCC Mix Design

    • Gradation

      • Coarse graded material

      • High amount of fines (passing #200), exceeding the 3% limit recommended by ASTM.