Concrete Pavements: How to Get the Biggest Bang for the Buck · 1 Concrete Pavements How to Get the...
Transcript of Concrete Pavements: How to Get the Biggest Bang for the Buck · 1 Concrete Pavements How to Get the...
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Concrete Pavements
How to Get the Biggest Bang for the Buck in Street/Local Road Applications
Brian Killingsworth, PE
VP, Pavement Structures NRMCA
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Concrete Overlays • Concrete Intersections • Sustainability
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Concrete Overlays • Concrete Intersections • Sustainability
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Pavement Long-Term Performance = Design + Drainage + Materials + Construction + Maintenance
MATERIALS
CONSTRUCTION
MAINTENANCE
DESIGN
DRAINAGE
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Typical Pavement Types
– Hot-Mixed Asphalt Concrete (HMAC)/Granular Base
– HMAC/Granular Base/Stabilized Subgrade
– Full Depth HMAC
– Continuously Reinforced Concrete Pavement (CRCP)
– Jointed Reinforced Concrete Pavement (JRCP)1
– Jointed Plain Concrete Pavement (**JPCP**)
– HMAC Overlay (Rehabilitation)
– Unbonded/Bonded Concrete Overlay (Rehabilitation)
Note 1: JRCP No Longer Recommended.
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Jointed Plain Concrete Pavement
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Definitions - Joints
Contraction/Sawcut Construction
Longitudinal
Isolation
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Longitudinal Joint
Transverse Joint
Subgrade Subbase
Surface Texture
Surface Smoothness or Rideability
THICKNESS DESIGN
Dowel Bars (may be optional)
Concrete Materials
Tiebars
Concrete Pavement Design
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Concrete Overlays • Concrete Intersections • Sustainability
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Rigid (or Semi-Rigid) Materials
• Conventional Concrete • Full Depth Reclamation With Cement • Roller Compacted Concrete • Pervious Concrete • Fiber Reinforced Concrete • Latex Modified Concrete
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Rigid Pavement Applications
• Highways and Interstates • Ramps • Shoulders • Roadways and Streets • Overlays • Intersections • Industrial Applications • Parking Lots • Bases
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Are Concrete Pavements Competitive?
• YES!
• When designed equivalent to the other pavement options that are being compared.
• When detailed appropriately (i.e. optimized).
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Are Concrete Pavements Competitive?
• Design Equivalence: Pavement designs using different surface material types or combinations of materials must be designed to be “equivalent”, i.e. comparable in terms of:
– Structural Capacity (i.e. Traffic Loading Applications) – Reliability (Similar Factors of Safety) – Service Life – Distress Failure Conditions
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Are Concrete Pavements Competitive?
• Optimized Design
– Avoid Overdesign by Using Appropriate Method – Refine Design Inputs to Match Requirements – Evaluate Joint Spacing – Maximize Maintenance (Methods & Timing) – Develop Multiple Cross-Sections w/Various Materials – Conduct Multiple Life-Cycle Cost Analyses
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Concrete Overlays • Concrete Intersections • Sustainability
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CONCRETE STRUCTURAL DESIGN OPTIMIZATION
Optimizing Design for Cost Effectiveness
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Design to Minimize Key Distresses
Transverse Cracking Joint Faulting
Under Slab Erosion Corner Cracking
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Pavement Design Methods
• 1993 AASHTO Design of Pavement Structures (DARWin)
• AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG or Pavement ME)
• ACI 325.12R-02: Guide for Design of Jointed Concrete Pavements for Streets and Local Roads
• American Concrete Pavement Association (ACPA) StreetPave12
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• Variables which can be optimized for projects:
– Improved Traffic Estimates (Now & Future)
– Reliability (What is the Right Factor of Safety?)
– Concrete Strength (Is Higher Always Better?)
– Edge Support Conditions (Does Adding Curb Help?)
Optimizing Designs
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Optimizing Designs
• Variables which can be optimized for projects:
– Subbase (Type, Thickness & Strength, if Needed)
– Reinforcing Steel (Is It Really Needed?)
– Load Transfer Condition (Are Dowels Needed?)
– Joint Sealing (How Necessary Is This?)
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When is a Subbase Needed?
• Subbases Have Little Influence on Required Concrete Pavement Thickness.
• What Conditions Need to Exist for Subbase Use?
– Heavy Loading (i.e. Trucks; ADTT > 100 - 200)
– Subgrade Susceptible to Pumping/Erosion (fine-grained)
– Water Available to Subgrade (infiltration or high water table)
– Risk of Deep Frost Penetration & Heave
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When is a Subbase Needed?
• If Conditions Exists, What Kind of Subbase?
– Granular (Crushed Stone)
– Treated (Asphalt or Cement)
– Recycled (Concrete or Asphalt)
– Permeable With or Without Drainage System
• Project Conditions Will Dictate…
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When is a Subbase Needed?
• If Conditions Exists, Are There Other Options?
– Subgrade Stabilization
– Soil Mixing
– Subsurface Drainage
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Pavements On Expansive Soils
Soil Heave Pavement Distress From Expansive Clay Subgrade
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Pavements On Expansive Soils – Mitigation Techniques
• Soil Treatment with Cement, Lime, or Fly Ash • Geosynthetics: Geotextiles or Geogrids • Removal and Replacement of High PI Soils • Drains or Barriers to Collect or Inhibit Moisture
Infiltration • Chemical Injection of Soil • Moisture Treatment • Soil Mixing
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Selecting the Right Treatment
• Soils and Environment Dependent
• Presence of Sulfates
• Material Availability and Cost
• Local Contractor Experience
• Project Schedule and Complexity
• Meet Owner Guidelines
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Don’t Forget…
• Mitigation Techniques: – May Need to be Combined, and – May Not Completely Solve the Problem!
Treatment of Upper Native Soil
Water Native Expansive Soil (High PI)
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Is Reinforcing Steel Required?
• Reinforcing Steel Does Not Contribute to Load Carrying Capacity of Pavement (i.e. Does Not Reduce Required Pavement Thickness).
• Primarily Used to Keep Cracks Tight.
• Cause of Pavement Distress Because of Steel Corrosion.
• Reduce Mid-Slab Cracking By Appropriate Joint Spacing. Thus, No Steel Is Needed!
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When Are Dowels Needed?
• Heavy Truck Traffic • Weak Subgrade Conditions • Poor Aggregate Interlock
• If Used:
– Concrete Thickness > 8 inches – Plate Dowels for Thinner Pavements
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When Is Joint Sealing Required?
• Always Should be Considered; However,
– Will the Joint Sealant be Maintained Over Time? – Is There Water or Wind Blown Material Present? – Is Subgrade Likely to Pump? – Is There Risk of Joints Opening (i.e. Expansive
Subgrade)?
• If These Risks Can be Minimized, Joint Sealing is NOT Necessary.
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CONCRETE MIXTURE DESIGN OPTIMIZATION
Optimizing Design for Cost Effectiveness
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Supplementary Cementitious Materials
Fly Ash Slag Cement
Silica Fume
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Fly Ash Use in Ready Mixed Concrete
• ACAA 2008 Survey – 72 M Tons Produced – 16 M Tons in Cement and Concrete – 41 M Tons Landfilled (58%)
• 2000 PCA Survey – >50% of all Ready Mixed Concrete had Fly Ash – 15 to 40% Fly Ash is Typical – High Volume Fly Ash Mixtures >40%
• What happens to concrete performance with increased fly ash?
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Supplementary Cementitious Materials
Properties of Fresh Concrete
Fly Ash
Slag Cement Silica Fume Type F Type C
Water Demand Lower Lower Lower Increase
Workability Increase Increase Increase Lower
Bleeding and Segregation Lower Lower Inc./Lower Lower
Setting Time Increase Inc./Lower Increase No Impact
Air Content Lower Lower No Impact Lower
Heat of Hydration Lower Inc./Lower Lower No Impact
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Supplementary Cementitious Materials
Properties of Hardened Concrete
Fly Ash
Slag Cement Silica Fume Type F Type C
Early Age Strength Gain Lower No Impact Inc./Lower Increase
Long Term Strength Gain Increase Increase Increase Increase
Permeability/Absorption Lower Lower Lower Lower
Alkali Silica Reactivity Lower Lower Lower Lower
Sulfate Resistance Increase No Impact Increase Increase
Freezing and Thawing No Impact No Impact No Impact No Impact
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High Volume Fly Ash: Bleeding and Finishing
• Low w/cm High Volume Fly Ash (HVFA) Concrete:
– May Have Low Bleeding
– Possibly Slow Bleed Rate
– Higher Chance of Plastic Shrinkage Cracking
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Cementitious Admixture Interactions
• Sometimes Very Delayed Setting (> 3 days), Poor Strength Development Possible
– Mostly in Hot Weather
– Aluminate-Sulfate Interactions
– Class C Fly Ash Contributes Aluminates
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Recycled Concrete as Aggregates
Concrete Structures Concrete Pavements
Returned Concrete
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Recycled Fine Aggregates
Foundry Sands and Slags
Crushed Concrete
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Effects on Fresh Properties
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Effects on Hardened Properties
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Effect on Durability
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Recycled Water
Concrete Wash Water (or Greywater)
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COMPASS: Mixture Optimization
Computer-Based Guidelines (Software Tool) For Job-Specific Optimization of Paving Concrete
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COMPASS: Mixture Optimization
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Concrete Overlays • Concrete Intersections • Sustainability
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Complementary Standard Details
• Standard Details That Should be Addressed:
– Joints (Contraction, Construction, Expansion) – Curbs, Curbs and Gutters – Pavement Junction – Bus Stop Pad – Driveways – Inlets/Manholes
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Concrete Overlays • Concrete Intersections • Sustainability
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• Can be placed on both concrete and asphalt pavements.
• Offers an economically sound solution with proven extended pavement life.
• Easy to correct problem areas like poor drainage.
• Can be Constructed Quickly.
Why Concrete Overlays?
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Concrete Overlays
Bonded Concrete Overlay of Concrete
Pavements
Bonded Concrete Overlay of
Asphalt Pavements
Bonded Concrete Overlay of Composite Pavements
Bonded Overlay Family
Unbonded Concrete Overlay of Concrete
Pavements
Unbonded Concrete Overlay of
Asphalt Pavements
Unbonded Concrete Overlay of Composite Pavements
Unbonded Overlay Family
Thinner Thicker
Bond is integral to design Old pavement is base
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Construction (Concrete Overlay of Existing Asphalt)
• Place concrete when surface temperature is <120°F.
• Conventional fixed-form or slip form placement used.
• Shotblast or mill (if needed) and clean surface thoroughly.
• Grout or epoxy bonding agents are not required (however local
conditions and experience will dictate).
• Texture Pavement for friction.
• Curing material must be placed as soon as possible (<30 minutes).
Full coverage is essential.
• Begin sawing as soon as possible (use of early entry saw is
recommended).
• Test mix throughout placement for QC.
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Typical Construction Sequence
1
4
2 3
5 6
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Paver Screeds
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Paver Screeds
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LOCAL ROAD OVERLAY How About an Example…
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Lombard is a suburb due west of Chicago in DuPage County, Illinois
Source: PCA from the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
Date
60 60 www.conexpoconagg.com Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
61 61 www.conexpoconagg.com Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
62 62 www.conexpoconagg.com Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
63 63 www.conexpoconagg.com Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
64 64 www.conexpoconagg.com Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
65 65 www.conexpoconagg.com Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
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f
Joints: 5.5 ft. X 5.5 ft. spacing
Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
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October 15, 2010
Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Concrete Overlays • Concrete Intersections • Sustainability
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Concrete Intersections - Considerations
• Typically Eliminates Rutting/Cracking Concerns • Complete reconstruction or inlay? • Concrete intersection construction limits • Thickness Design • Subgrade and subbase requirements • Jointing detail • Pavement profiles • Concrete materials • Concrete to asphalt transitions • Traffic detection systems • Coordination with local agencies
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Concrete Intersections - Timing
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Concrete Intersections - Timing
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Concrete Intersections - Timing
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Concrete Intersections - Timing
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Concrete Intersections - Timing
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How to Get the Biggest Bang for the Buck
• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Life Cycle Cost Analysis • Concrete Overlays • Sustainability
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Concrete Sustainability
• Concrete streets last longer with less maintenance.
• Concrete streets reduce Heat Island Effect.
• Concrete streets are safer at night: – lighter color surface reflects more light.
• Concrete can be used for stormwater management.
• Concrete is locally produced so you can buy at home and can be recycled at the end of its life.
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The Concrete Sustainability Hub
http://web.mit.edu/cshub/index.html
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Thank You!
Brian Killingsworth, P.E. Vice President, Pavement Structures
National Ready Mixed Concrete Association
Phone: (830) 438-2690 Mobile: (210) 508-4923
http://www.nrmca.org/about/Staff-Bio-BKillingsworth.asp
http://www.nrmca.org/