Concrete Pavement Jointing and Details · 2020-04-27 · vRecognize why joints are needed in a concrete pavement. vStudy dowel and tie bars and know when and how to use them. vLearn

Don A. Clem, P.E.Vice-President – Local Paving, NRMCA

Amanda Hult, PESenior Director, Local Paving, NRMCA

Concrete Pavement Jointing and Details

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National Ready Mixed Concrete Association

• National Trade Association – Established in 1930• HQ in Alexandria, VA• 1,400+ Member Companies• NRMCA Represents ~75% of North American Ready Mixed Production• Mission - Serve Industry and Partners Through:

• Compliance and Operations

• Engineering

• Government Affairs

• Local Paving: Pave Ahead™ Initiative

• Structures and Sustainability: Build With Strength™ Initiative

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Your Instructors Today…

• Don A. Clem, P.E.– NRMCA Local Paving, Vice President, Northwest Rocky Mountains– 41 Years in Practice– Pavement Design, Concrete Overlays, Forensics

• Amanda Hult, P.E.– NRMCA Local Paving, Senior Director, South Central Region– 20+ Years in Practice– Civil Design – Streets / Local Roads & Parking Lots

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NRMCA Super Sponsors

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NRMCA Disclaimer

This presentation has been prepared solely for information purposes. It is intended solely for the use of professional personnel, competent to evaluate the significance and limitations of its content, and who will accept full responsibility for the application of the material it contains. The National Ready Mixed Concrete Association and any other organizations cooperating in the preparation of this presentation strive for accuracy but disclaim any and all responsibility for application of the stated principles or for the accuracy of the content or sources and shall not be liable for any loss or damage arising from reliance on or use of any content or principles contained in this presentation. Unless otherwise indicated, all materials in this presentation are copyrighted to the National Ready Mixed Concrete Association. All rights reserved. Therefore reproduction, modification or retransmission in any form is strictly prohibited without the prior written permission of the National Ready Mixed Concrete Association. ©2015 National Ready Mixed Concrete Association.

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Instructions

• Everyone is muted• Webinar is being recorded• Type questions in the question box• Download the handouts in the GoToWebinar control panel• Credit for course

– Based on attendance– Survey (Quiz) – In follow-up e-mail, not required, but encouraged– Certificate – In follow-up e-mail 1 hour after webinar– AIA members – We will register your attendance with AIA-CES if you provided AIA number

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About the Course

Learning Units (LU) or Professional Development Hours (PDH)• AIA-CES Course - 1.0 LU| Elective or 1.0 PDH

• Learning Objectives:

v Recognize why joints are needed in a concrete pavement.v Study dowel and tie bars and know when and how to use them.v Learn about the three joint types normally specified for a concrete pavement.v Understand the various types of equipment used to form joints.

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ACI 330R-08: Parking Lots and ACI 325.12R-02: Streets and Roads

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American Concrete Pavement Association (ACPA) & CP Technology Center

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Concrete Pavement Jointing and Details - Agenda

• Concrete Pavement Terminology• Why are Joints Needed• Joint Spacing• Types of Joints

– Contraction (control)– Construction– Isolation

• Jointing Plan• Jointing and Load Transfer• Reinforcing Steel• Joint Sealing• Additional Resources

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Pavement Design

Longitudinal Joint

Transverse Joint

SubgradeSubbase

Surface Texture

Surface Smoothnessor Rideability

THICKNESS DESIGN

Dowel Bars

Concrete Materials

Tiebars

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What Causes Pavement Distress?

Traffic Loading

Environmental Conditions

Material Properties of

Pavement Layers

Stress, Strain, and Deflection

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Concrete volume change (and cracking) behavior is the basis of many jointing and construction procedure recommendations.

Concrete Volume Change Effects and Jointing

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Shrinkage + Restraint = Cracking

Cracking results from combined effects of restraint and shrinkage(drying and/or thermal)……whenever resulting tensile stresses exceed tensile strength.

Drying Shrinkage and Cracking

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Why Are Joints Needed in Concrete Pavement?

• Control the location, width, and appearance of expected cracks.

• Accommodate normal slab movements.

• Divide pavement into practical construction elements

• Provide load transfer where needed.

• Minimize performance implications of any random (unexpected) cracks.

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Typical Crack Formation Sequence

• Initial cracking is caused by shrinkage and temperature variations

• Initial cracks vary in length from about 40’ to 150’• Then, curling and warping stresses, and loading of the

pavement cause intermediate cracking, as shown in Fig. 2a

• We strive to design joints as shown in Fig. 2b below

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Joint Design & Layout Affect Performance

Spacing Issue

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The extent of cracking due to key influences is somewhat predictable; joints can be spaced accordingly.

Maximum Recommended Spacing (ACI 330)

Exception: good design may call for even closer joint spacing due to load transfer considerations.

Joint Spacing

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Rules of Thumb for Jointing & Slab Dimensions

• Maximum Spacing:

– Recommendation of 2.5 times the depth in feet

– For example: 4” thick = 10’ maximum (4 x 2.5)

• Panel shall be kept as square as possible

– L:W of 1 ¼ -1½:1 (Maximum length to width ratio)

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Slab Length vs. Pavement Thickness Relationships

slab thickness but decrease with increased (stiffer) foundation support conditions.

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Types of Joints: Schematic Representation

Contraction or Control

Construction

Isolation

CONTRACTION (CONTROL) JOINTS

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Joint Sawing/Forming

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Tooled Control Joints

Advantages:

• Simplest to make.

• Most reliable crack initiation.

Disadvantages:

• Most noticeable joint.

• Not smoothest for rolling wheels.

• Not designed for sealers / fillers.

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Control Joints Inserts

Advantages:

• Almost invisible.

• Somewhat resistant to intrusion of water and debris even when unsealed.

• Provides good rideability.

• Reliable crack initiation.

• Fast and economical.

Disadvantages:

• Learning curve for crew.

• Can ravel or spall if not installed plumb.

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Spalling Results If The Insert Is Not Plumb

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Advantages:• Makes best sealant reservoir.

• Not as noticeable as tooled.

• Smoothest for wheels.

Disadvantages:

• Timing is critical to success -

least reliable crack initiation

with gravel aggregates.

• Expensive to make.

Sawcut Control Joints

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Rules of Thumb for Sawcut Joints

• Depth:

– Conventional Sawing:

• Minimum of ¼ of the depth: e.g. 8” thick = 2” deep

• ACPA recommends minimum of 1/3 of the depth for longitudinal joints

– Early Entry Sawing:

• Typical 1” to 1.5” depth

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Sawcut joints with conventional saws must be

made within 4-12 hours after final finishing.

This joint was sawed at correct time

This one was sawed too late

Timing of Joint Sawing–A Critical Factor

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Early Entry “Dry Cut” Saws

• Designed to initiate cracks with a shallow cut made much earlier than with wet-cut saws.• Timing - “window of opportunity” is 1 to 2 hours.

CONSTRUCTION JOINTS

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Construction joints are used between separate concrete placements, typically along placement lane edges.

formed or slipped face

Butt joints are recommended for most parking lots where load transfer needs are minimal.

1st placement2nd placement

Use of Construction Joints

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Keyway Dimensions

D

0.1D

0.2D

1:4 Slope

0.2D

Trapezoidal Half-round

No longer recommended for light traffic pavements!

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Keyway Construction Joints in a 5-inch Thick pavement

ISOLATION JOINTS

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…are sometimes called expansion joints but should generally not be used to provide for expansion. They provide no load transfer and should not be used as regularly spaced joints in a joint layout. Their proper use is to isolate fixed objects, providing for slight differential settlement without damaging the pavement.

Isolation Joints

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Diagonal

Isolationjoint

Inlet

Isolation joint

Circular

Isolationjoint

Square with Fillets

Isolation joint

Inlet - Round

Isolationjoint

Telescoping Manhole

No boxout orisolation jointnecessary

None

Isolationjointaroundperimeter

SquareIsolationjoint

Reinforcing barsrecommended tohold cracks tight

Common Details for Isolation of Fixtures

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Examples - Isolation of Fixtures

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Expansion Joints

• Expansion joints are NOT isolation Joints• Placed in a pavement to allow for anticipated expansion• Only needed when:

1. the pavement is divided into long panels (>60 feet) without contraction joints in between2. the pavement is constructed while ambient temperatures are below 40 degrees F3. the contraction joints are allowed to be infiltrated by large incompressible materials 4. the pavement is constructed of materials that in the past have shown high expansion

characteristics• Under normal conditions, regularly placed expansion joints (IE every 100 feet) are not

necessary

Longitudinal Joints

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Longitudinal Joints

• Spacing Criteria:

– Spacing of 10 to 13 feet serves as both crack control and lane delineation.

– Lanes (driveways) that are greater than 13’ require a longitudinal joint.

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Tie Bar Dimensions and Spacing (US)

Table 4.1—Tie bar dimensions and spacings (commonly Grade 60)*

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Typical Jointing Plan

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Jointing Plans and Details

• Designer provides basic recommendations regarding joint layout and other joint considerations that affect pavement performance. May also provide jointing plan.

• Materials and construction specifications provide requirements for acceptable joint placement methods and the equipment that may be used.

• Contractor implements the above requirements by following or developing a comprehensive jointing plan.

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Joint Layout Guidelines

• What You Should Do:

– Jointing plan drawn by designer of record, or submitted by contractor & approved by designer.

– Match existing joints or cracks.

– Cut at the proper time.

– Place joints to meet in-pavement structures.

– Adjust spacings to avoid small panels or angles.

– Intersect curves radially, edges perpendicular.

– Keep panels square.

• What You Should Avoid:

– Jointing plan left to field personnel with no oversight.

– Slabs < 1 ft. wide.

– Slabs > 15 ft. wide.

– Angles < 60º (90º is best).

– Creating interior corners.

– Odd Shapes (keep slabs square).

– Offset (staggered) joints.

– Isolation (unthickened) joints in traffic areas.

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Carry joint through curb(integral curb shown) Intersect joints (Avoids

acute angles)

Intersect at corners

Jointing Layouts: Corners, acute angles, & edges with extreme curvature

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Meet structures at corners

Avoid acute angles(Intersect at perpendicular)

Jointing Layouts: Corners, Acute Angles, edges with extreme curvature

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Thickened Edges

Concrete at pavement edges or along isolation joints that will support wheel loads may be thickened to provide extra support.

Source: ACPA

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Load

Load

Excessive deflections and flexure - same as free edge loading.

Deflections and flexural stresses are reduced.

Definition – Load Transfer

• Shear strength provided at joints (or cracks) by dowels or other features, aggregate interlock, or contact friction.

• Significantly reduces load-related deflection.

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Load Transfer Efficiency (LTE)

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Load Transfer

• Load Transfer is a Function of:

– Aggregate Interlock

– Stiffness of Supporting Layers

– Mechanical Devices (i.e. Dowels)

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Aggregate Interlock

• Effectiveness depends on the crack width and the spacing between joints.

• Good for lighter traffic.

• For ADTT greater than 100, aggregate interlock may not be sufficient.

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Factors That Enhance Aggregate Interlock Effectiveness:

• Larger coarse aggregate sizes

• Angular coarse aggregate texture (crushed vs. natural)

• Thicker slabs

• Shorter joint spacing

• Stiff subbases

• Edge support

• Coarse-grained subgrade soils

• Functioning drainage system

Aggregate interlock load transfer may not be sufficient for high volumes of heavy truck traffic!

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Stabilized Subgrades or Subbases in Relation to Joint Considerations

• Reduces:– Potential joint deflection,– Erosion potential.

• Improves working surface, if necessary.

• Extend 2’ beyond an unsupported slab edge.

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Doweled Joints

• Not needed on low volume streets and roads.– Especially when transverse joint spacing is less than 15 feet.

• May be justified when k values are less than 75 psi/in.

• Generally, pavement must be at least 7”-8” thick to accommodate conventional dowels.

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Dowels…

Generally not used in low volume situations. May be needed when there is poor subgrade and/or many trucks.

Dowels provide load transfer and allow the joints to move.

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Smooth Round Dowels

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Round Dowels in Baskets

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Plate Dowels – Widely Used in Floor Slabs

• Now being used in some parking areas / industrial pavements.

• Accommodate some differential movement longitudinally along the joint.

• Greater concrete bearing area, less stress.

• Can be effectively used in thinner slabs than round dowels.

• Efficient use of steel.

• Diamond shapes for formed construction joints.

• Trapezoidal shapes in baskets for control joints.

Diamond dowels for construction joints:Dowel receptacle is nailed to form prior to placement.

Dowel is inserted into receptacle after form

removal.

Construction joints using diamond dowel system

Plate/Diamond dowel system for both control joints and construction joints – prior to concrete placement

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Distributed Steel Reinforcement

…

…

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PLACEMENT OF STEEL SHALL BE IN TOP 1/3 OF PAVEMENT SECTION


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Steel Placed Too Low

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Joint Sealing

• Topic of some debate.

• Sealants must be maintained and drainage design must be effective.

• Low cost poured sealants not durable.

• Some joint types difficult to seal.

• Factors to consider in whether or not to seal joints:

– Traffic level– Soil types & local performance– Subbase use– Presence of wind blown debris

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Joint Sealing

Minimize surface water & incompressible material into pavement system in an attempt to reduce:

-Subgrade softening

-Pumping/Faulting

-Erosion of fines

-Spalling

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To Seal or Not to Seal?

• Sealing joints & maintaining well-sealed joints MAY improve performance of the pavement; research into this topic is ongoing…

• … however, some agencies/owners no longer require joints to be sealed under certain conditions

www.sealnoseal.org

http://www.sealnoseal.org/

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Joint Sealants

• Three basic types are:

– Hot poured

– Silicone

– Preformed

• Applicable specs for each type.

• Specialty types (e.g., jet fuel resistant, self-leveling and no tooling, etc.), and backer rods are available in literature and from manufacturers.

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Sealing? Make Certain the Joint is Clean!

• All sealed joints must be cleaned immediately behind saw cutting or joint widening and immediately prior to sealing operations:

– Removes saw-cut slurry, soil, sand, etc.

• Cleanliness of both joint faces is extremely important to concrete/sealant bond.

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It’s Not Hard to Check…

• If wiping a finger along the face picks up dirt or dust, recleaning should be done before sealing!

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Sealant Selection

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NRMCA Jointing Details

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Additional documents on jointing

https://paveahead.com/register/

Pave Ahead™

Concrete Pavement Design Center


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• Design recommendations• Cost comparisons including life cycle costs• Specification review• Ready mixed products:

– Conventional concrete (full depth and overlays)– Pervious concrete– Roller compacted concrete– Cement slurry for full depth reclamation (FDR)


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Local Paving Division: State and Regional Assignments

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Local Paving Division: State and Regional Assignments

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www.paveahead.com/education

• More Concrete Pavement professional development:

– Each Thursday beginning at 2:00 pm EDT

– April 02 Designing Concrete Parking Lots and Streets

– April 09 Designing Concrete Industrial Pavements

– April 16 Soils 101: What to Know for a Successful Paving Project

– April 23 Concrete Pavement Jointing and Details

– April 30 Materials and Construction Specifications for Concrete Pavement Projects

– May 07 Concrete Street and Parking Lot Maintenance and Repair

– May 14 Concrete Overlays of Existing Asphalt Surfaced Streets and Parking Lots

– May 21 Concrete Trail Design

• Concrete Buildings Webinar Series: https://buildwithstrength.com/education/

– Each Wednesday beginning at 2:00 pm EDT

https://buildwithstrength.com/education/

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www.paveahead.com/education• More Concrete Pavement professional development:

– Each Thursday beginning at 2:00 pm EDT

– May 28 Designing Pervious Concrete

– June 4 Specifying Pervious Concrete

– June 11 Installing Pervious Concrete

– June 18 Maintenance Guidelines for Pervious Concrete

• Portland Cement Association Webinar Series: www.cement.org/events

– Each Wednesday beginning at 9:00 am EDT

– April 22 Full-Depth Reclamation with Cement

– April 29 Lightweight Cellular Concrete for Geotechnical Applications

– May 6 Roller-Compacted Concrete Pavements

– May 13 Cement Stabilized Subgrade Soils

– May 20 Cement-Based Water Resource Applications

https://www.cement.org/events

Amanda Hult, PESr. Director – Local Paving

Don A. Clem, PEVP – Local Paving

Documents

Concrete Pavement Jointing and Details · 2020-04-27 · vRecognize why joints are needed in a concrete pavement. vStudy dowel and tie bars and know when and how to use them. vLearn