concrete pavements: how to get the biggest bang for the buck · 1 concrete pavements how to get the...

1 1 www.conexpoconagg.com

Concrete Pavements

How to Get the Biggest Bang for the Buck in Street/Local Road Applications

Brian Killingsworth, PE

VP, Pavement Structures NRMCA


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


Pavement Long-Term Performance = Design + Drainage + Materials + Construction + Maintenance

MATERIALS

CONSTRUCTION

MAINTENANCE

DESIGN

DRAINAGE


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.


Jointed Plain Concrete Pavement


Definitions - Joints

Contraction/Sawcut Construction

Longitudinal

Isolation


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


Rigid (or Semi-Rigid) Materials

• Conventional Concrete • Full Depth Reclamation With Cement • Roller Compacted Concrete • Pervious Concrete • Fiber Reinforced Concrete • Latex Modified Concrete


Rigid Pavement Applications

• Highways and Interstates • Ramps • Shoulders • Roadways and Streets • Overlays • Intersections • Industrial Applications • Parking Lots • Bases


Are Concrete Pavements Competitive?

• YES!

• When designed equivalent to the other pavement options that are being compared.

• When detailed appropriately (i.e. optimized).



• 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



• 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


CONCRETE STRUCTURAL DESIGN OPTIMIZATION

Optimizing Design for Cost Effectiveness


Design to Minimize Key Distresses

Transverse Cracking Joint Faulting

Under Slab Erosion Corner Cracking


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


• 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


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?)


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



• 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…



• If Conditions Exists, Are There Other Options?

– Subgrade Stabilization

– Soil Mixing

– Subsurface Drainage


Pavements On Expansive Soils

Soil Heave Pavement Distress From Expansive Clay Subgrade


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


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


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)


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!


When Are Dowels Needed?

• Heavy Truck Traffic • Weak Subgrade Conditions • Poor Aggregate Interlock

• If Used:

– Concrete Thickness > 8 inches – Plate Dowels for Thinner Pavements


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.


CONCRETE MIXTURE DESIGN OPTIMIZATION

Optimizing Design for Cost Effectiveness


Supplementary Cementitious Materials

Fly Ash Slag Cement

Silica Fume


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?



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



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


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


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


Recycled Concrete as Aggregates

Concrete Structures Concrete Pavements

Returned Concrete


Recycled Fine Aggregates

Foundry Sands and Slags

Crushed Concrete


RCA for Pavements (ACPA 2009)

http://www.acpa.org/

http://www.acpa.org/


Effects on Fresh Properties


Effects on Hardened Properties


Effect on Durability


Recycled Water

Concrete Wash Water (or Greywater)


COMPASS: Mixture Optimization

Computer-Based Guidelines (Software Tool) For Job-Specific Optimization of Paving Concrete


COMPASS: Mixture Optimization


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


• 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?


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


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.


Typical Construction Sequence

1

4

2 3

5 6


Paver Screeds


LOCAL ROAD OVERLAY How About an Example…


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


f

Joints: 5.5 ft. X 5.5 ft. spacing

Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11


October 15, 2010

Source: Presented by PCA at the ACI & NRMCA Concrete Solutions Seminar, 9/20/11


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


Concrete Intersections - Timing



• Definitions and Nomenclature • Types of Concrete Pavements? • Design Optimization • Complimentary Design Details • Life Cycle Cost Analysis • Concrete Overlays • Sustainability


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.


The Concrete Sustainability Hub

http://web.mit.edu/cshub/index.html

http://web.mit.edu/cshub/index.html


Thank You!

Brian Killingsworth, P.E. Vice President, Pavement Structures

National Ready Mixed Concrete Association

Phone: (830) 438-2690 Mobile: (210) 508-4923

[email protected]

http://www.nrmca.org/about/Staff-Bio-BKillingsworth.asp

http://www.nrmca.org/

mailto:[email protected]






http://www.nrmca.org/

concrete pavements: how to get the biggest bang for the buck · 1 concrete pavements how to get the...

Documents