National Concrete Consortium Rapid City, South Dakota

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Partial Depth Crack and Joint Rehabilitation

Dale S. Harrington P.E. Representing the National Concrete Technically Center

National Concrete Consortium Rapid City, South Dakota

September 13, 2011

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About the Guide

• The purpose of this guide is to provide information and techniques on completing partial-depth repairs in the upper 1/3 to 1/2 of the pavement thickness.

• Principal Authors

- Daniel P. Frentress, Frentress Enterprises, LLC

- Dale S. Harrington, PE, Principal Senior Engineer, Snyder & Associates, Inc.

• Plan to publish PDR Guide late fall 2011

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Acknowledgements • Gratefully acknowledge the contributions of the project’s

Technical Advisory Committee: 1. Andy Bennett, Michigan DOT 2. John Cunningham, ICPA 3. Dan DeGraaf, Michigan ACPA 4. Larry Engbrecht, South Dakota Chapter ACPA 5. Andy Gisi, Kansas DOT 6. Todd LaTorella, MO/KS ACPA 7. Kevin McMullen, Wisconsin ACPA 8. Kevin Merryman, Iowa DOT 9. Jim Parry, Wisconsin DOT 10. John Roberts, IGGA 11. Robert Rodden, ACPA 12. Matt Ross, Penhall 13. Doug Schwartz, Gateway Engineering and Training 14. Gordon Smith, ICPA 15. Kurt Smith, Applied Pavement Technology 16. Sam Tyson, FHWA 17. Leif Wathne, ACPA 18. Matt Zeller, Concrete Paving Association of Minnesota

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Introduction

• Existing load transfer devices are functional

• Cost ≈ $25 to $30 / sq. ft.

• Cost on Major Quantities of Longitudinal can be $12 - $20 / sq. ft.

• Cost on night work can be as high as $55 / sq. ft.

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Three Types of Partial Depth Repairs

Type 1 - Spots Repairs (SR) - Pay by Square Foot. Type 2 - Long Joint/Crack Repairs (LJCR) - Pay by Linear foot Type 3 - Bottom Half Repairs (BHR)

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Type 1 – Conventional Spot Repairs of Joints, Cracks and Spalls

• Spot repairs are at least 15 inches long, but less than 6 feet along a transverse or longitudinal crack or joint

• When spot repair areas are closer than 2 ft apart, they should be combined

Crack Joint Spalling

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• When the saw and chip method is used to form the edges of the repair, the edges are tapered using a small (10- to 30-lb.) jackhammer to remove the vertical edges left by the sawing operation

• Compression relief must be provided for the full depth of the patch and should extend at least ½ inch beyond if possible

Type 1 (saw and chip) spot repairs

Chip out concrete 2” from saw cut with lightweight jackhammer at 30-60 degree angle.

2”

Saw and Chip Removal

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• As long as there is an adequate volume of repairs to be made on a particular project, milling for spot repairs can be completed faster than the chip and saw method

• Payments for joint repairs are by the square ft of completed patch area for Type I repairs (less than 6 ft in length)

• Typically crack partial depth repairs are paid by the square foot for any length of a crack repair

Type 1 (milled) spot repairs Type 1 spot milling

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Type 2 – Extended Length Repairs

• Longitudinal or transverse joints (Type 2A) • Cracks (Type 2B) longer than 6 ft.

Joint (Long) Joint Crack (Transverse)

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• Type 2A (Joints), the joint re-establishments typically by sawing

• Type 2B (cracks) the crack pressure relief is preformed joint material in the crack itself.

• Removal of the existing pavement is usually by milling

Type 2 (milled) Extended Length Repair

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• Payments for Type 2A joint repairs are generally by the linear ft.

• Payments for Type 2B crack repairs are by square feet which is the same as Type 1.

• Widening of the milled area has to be performed to obtain a minimum space (3 inches).

Type 2B – Crack Milling V-head Milling (Type 1 & 2)

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Kansas Approach

• To prevent edge chipping from milling Kansas saws pavement 2” to 3” from milled edge.

• Remove pavement to edge of saw cut.

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Bottom-Half Spot Repairs

• Used for spot locations where the deterioration along the partial-depth repair exceeds T/2 in depth thus requiring a full-depth repair.

Type 3 – (Chip) Bottom – Half Corner Joint Repair Candidates

Type 3 Repair – Removal by Milling and Chipping

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Bottom-Half Spot Repairs • For work performed in the bottom half of the pavement with

payment for the bottom half under Type 3 repair and top half under a Type 1 repair

• Should be limited to 18 in. long

Type 3 – Bottom – Half Repairs

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Material Selection for Partial-Depth Repairs Patch Material

• Material selection for partial-depth repairs depends on these factors: - Allowable lane closure time (strength of material)

- Shrinkage Characteristics

- Coefficient of Thermal Expansion

- Ambient temperature

- Cost

- Size of repair

- Estimated performance

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• Repair materials for partial-depth repairs are generally classified cementitious, polymeric, or bituminous

• Concrete mixes along with a wide variety of rapid-setting and high-early-strength proprietary materials have been developed

• High-quality portland cement concrete is generally accepted as the most appropriate material for the repair of existing concrete pavements

• Concrete mix requires use of small-sized, coarse aggregate, usually less than 1/2 in.

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• Should be a low-slump mixture of air-entrained concrete

• Water-cement ratio not exceeding 0.44

• Rich mixtures (up to 8 bags of cement)

• Gain strength rapidly

• Insulating layers can be used to retain the heat of hydration and reduce curing time

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• A mix developed by the Minnesota DOT, called 3U18, has been very successful for more than 30 years

• Results in an 18± hour opening strength of 2,500 psi

• Earlier opening times can be achieved with other appropriate admixtures

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• Cementitious 3U18 Recommended for Use in Partial-Depth Repairs - 850 lbs Type I Cement

- 295 lbs of water

- 1,328 lbs of coarse aggregate

- 1,328 lbs of sand

- Target W/C of 0.35

- Type E Water Reducing and Accelerator

- 6.5% air

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• Cementitious 3U18 Recommended for Use in Partial-Depth Repairs - Maximum 1 in. slump (measured after allowing to

set 5 minutes after mixing)

- Cure time of 18± hours

- Fine aggregate gradation of 100% passing 3/8 in. sieve

- Coarse Aggregate gradation of o 100% passing the 3/8 in. sieve

o 55% - 95% passing the #4 sieve

o Not more than 5% shall pass the #50 sieve

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Bonding (Grout) Agent

• Sand-cement grouts have proven adequate when used as bonding agents with concrete repair materials. - 2 parts Type I cement

- 1 part water (may be more or less to develop a creamy consistency)

- 1 part sand

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Bonding (Grout) Agent

• The Kansas DOT uses a different approach regarding bonding agents.

• Use a more watery mix which helps cool and pre-wets the existing concrete pavement before placement. - 1 part Type I cement

- 3 parts water

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Type 1 and 2 – Mill and Removal

Milling along the joint or crack

Milling perpendicular to the joint or crack

Type 2B Crack Milling

Rounded Milling (Type 1 & 2)

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Repair Area Preparation • Surface of

the repair area must be clean.

Sweeping loose materials

Sounding with hammer

Sandblasting to remove loose debris

Air Blasting for final cleaning

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Compression Relief – Joint/Crack • Most frequent failure of partial-depth repairs occurs from

excessive compressive stresses on the repair material at the repaired joint or crack.

Illustration of joint preparation using bond breaker

Illustration of joint preparation without bond breaker

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Compression Relief – Joint/Crack • To prevent failure, a strip of polystyrene or polyethylene

compressible material is typically placed in short Type I joints or cracks and Type 2B crack repairs (to the depth of the repair) to act as a bond breaker.

View of cardboard cut to fit irregular random crack for Type 2B crack repair

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Bonding Agent Application • Cleaning the surface of the existing concrete

• Just prior to placement of the repair material, coat the surface with a sand-cement grout to ensure complete bonding of the repair material

• Mixed to the creamy consistency

• Placed immediately before the repair material, so the grout doesn’t set

Cement grout of Type 2A – Joint Repair

Cement grout of Type 3 – Bottom Half

Repair

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Placement of Compression Relief • Waxed cardboard fits with the irregular nature of random

cracks.

• Has the ability to maintain its rigidity for the concrete placement.

• Place a foot on the cardboard during concrete vibration, so it does not float.

Concrete placement for Type 1 repair using waxed cardboard

Type 2B – Crack Repair

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Placement and Consolidation of Material

• Repair materials should not be placed when the air temperature or pavement temperature is below 40ºF.

• Additional precautions, such as the use of warm water, insulating covers, and longer cure times, may be required at temperatures below 55ºF.

• Failure to properly consolidate concrete results in poor repair durability, spalling, and rapid deterioration.

Consolidation of Repair Material for Type 2A Joint Repair

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Sawing Relief Joints • Type 1 and Type 2A joints have been successfully sawed

to create compression relief.

• Tooling of the joint can be done to help create a weak plane during concrete placement.

• Joint reservoir shall be wider than the crack under the repair.

Tooling of the joint

Sawing following tool of the joint

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Screeding and Finishing • Screed the repair surface on each side of the compression

relief. • At least two passes should be made to ensure a smooth

repair surface. • Paint a sand-cement grout (the same grout as used for

bonding. • At the edges of the repair to impede delamination of the

patch.

Placement of grout at edge of partial-depth repair

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Curing

Cutting excess compression relief board of Type 2B crack repair

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Curing

• Prevent moisture loss

• White-pigmented curing compound commonly used (some require 1.5 to 2 times normal rate)

• Opening to traffic - Mix / temperature

dependent - Common values: 2,000 to 3,000 psi

P.D.P. Have large surface areas in relation to their volumes (which can lead to rapid moisture loss)

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Completed Repairs

Completed Type 2A joint repair

Completed Type 1 crack repair

Completed Type 2B crack repair

Completed Type 3 repair

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Optional Diamond Grinding

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Joint Sealing

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Examples of Long Lasting Partial Depth Repairs

20 year old Type 2A longitudinal and transverse partial depth repairs in

Hopkins, MN

Close up of partial depth patch in Hopkins, MN done in 1991 and

picture taken 2011

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Crack or Joint Repair When Deterioration is in the Lower Half of the Slab

Remove unsound concrete with 35 lb Max. chipping hammer

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Short-Term Partial Depth Patch Fill Void Below Joint

• Use Sand to provide compression relief in milled crack (no lockup)

• Must use caution when needing to do a lot of this before patching

• Repair will not last as long as one placed in sound concrete

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Short-Term Partial Depth Patch Precautionary Note in Specs

• Sand can prevent locking of the joints together due to concrete infiltration when placing repairs.

• This will probably result in a reduced repair life.

• The following is an example of over using the sand principle.

• Duct tape is an excellent way to prevent bond on exposed old dowel bars.

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THANK YOU!

National Concrete Pavement Technology Center

Documents

National Concrete Consortium Rapid City, South Dakota