Difference between revisions of "304 - Rubbilizing Existing PCC Pavement"

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<center><span STYLE="font: 60pt arial;">'''304'''</span></center>
 
<center><span STYLE="font: 60pt arial;">'''304'''</span></center>
  
<center><span STYLE="font: 40pt arial;">'''Rubberizing Portland Cement Concrete Pavement'''</span></center>
+
<center><span STYLE="font: 40pt arial;">'''Rubblizing Portland Cement Concrete Pavement'''</span></center>
  
<center>[http://mdotcf.state.mi.us/public/specbook/files/2012/304%20Rubbilizing%20PCC%20Pavt.pdf 2012 STANDARD SPECIFICATIONS FOR CONSTRUCTION - SECTION 304]</center>
 
  
  
==GENERAL==
 
  
This work will consist of rubblizing existing concrete pavements to be used as a base course for Hot Mix Asphalt (HMA) pavements.
+
==[[#GENERAL|GENERAL DESCRIPTION]]==
 +
=== Definitions of Terms ===
 +
'''Aggregate Filler:''' Aggregate filler is additional aggregate required to adjust rubblized pavement to meet specified plan grades.
 +
 
 +
'''Portland Cement Concrete (PCC):''' PCC is a material used within a pavement system as a roadway surface.
 +
 
 +
'''Rubblizing:''' Rubblizing is the process of disintegrating concrete pavement or structures using hydraulic breakers, jackhammers, or specialized machinery to produce rubble suitable as a base course for hot mix asphalt (HMA).
 +
 
 +
'''Sawcut, Rubblize:''' A full-depth relief sawcut between rubblized pavement and pavement areas planned to be retained.
 +
 
 +
=== General Overview ===
 +
Rubblizing PCC pavement is a method employed in road rehabilitation and reconstruction. It entails breaking existing concrete pavement into small, irregular pieces of rubble using specialized machinery like resonant pavement breakers or high-energy impact breakers. This process allows for in-place recycling of existing concrete, providing a suitable base for the construction of a new asphalt overlay. Rubblizing is chosen for its cost-effectiveness, reduced construction time, and minimal disruption to traffic compared to conventional pavement removal methods. It can be used on both reinforced and non-reinforced pavement. For an overview of operations, refer to [https://www.youtube.com/watch?v=0Z-7ipTvDF0 HMA Paving Operations Video 6 – Rubblizing (youtube.com)].
  
 
{{top}}
 
{{top}}
  
===Equipment===
+
==[[#MATERIALS|MATERIALS]]==
 +
All materials must meet acceptance requirements in the Materials Source Guide and be listed on the Contractor-provided Material Source Lists in the project files.
 +
 
 +
=== Dense-Graded Aggregate (21AA) ===
 +
If additional material is needed after pavement rubblization, only dense-graded 21AA aggregate is permitted for aggregate filler.
 +
 
 +
The aggregate must meet the requirements in Section 902 of the Standard Specifications for Construction and the Aggregate Inspection Manual. Aggregate filler can consist of:
 +
* Limestone
 +
* Recycled concrete
 +
* Slag aggregate
 +
 
 +
Loss by wash should be in accordance with Section 902 of the Standard Specifications for Construction.
 +
 
 +
{| class="wikitable"
 +
|+
 +
|-
 +
| [[File:304-002.png|300px|thumb|center|'''Filler Aggregate Placed over Crushed Pavement''']]
 +
|-
 +
|}
 +
 
  
Equipment will be as listed in subsection [http://mdotcf.state.mi.us/public/specbook/files/2012/304%20Rubbilizing%20PCC%20Pavt.pdf 304.03] of the Standard Specifications for Construction.  The existing pavement condition will determine the size of the shoe the Contractor will be able to use on the resonant frequency pavement breaking machine.  If the pavement is demolishing easily and with little oversize, a wider shoe could possibly be used.
 
  
 
{{top}}
 
{{top}}
  
==MATERIALS==
+
==[[#EQUIPMENT|EQUIPMENT]]==
 +
The following equipment is typically used for construction of a rubblizing PCC pavement:
 +
* Resonant frequency breaker
 +
* Multi-impact hammer
 +
* Bulldozer
 +
* Grader
 +
* Single or dual drum rollers
 +
* Z-grid roller
 +
* Pneumatic tire roller
 +
* Water injection system
  
Filler aggregate will meet the Open-graded Aggregate 3G Specification, Section [http://mdotcf.state.mi.us/public/specbook/files/2012/902%20Aggregate.pdf 902] of the Standard Specifications for Construction.
+
=== Description of Equipment ===
 +
Rubblizing is performed by either a resonant frequency breaker or a multi-impact hammer. Once the pavement is rubbilized, fine grading is performed with a bulldozer or grader to achieve the correct cross-section. The rubblized pavement is then compacted with a z-grid roller to achieve the required density. Water injection systems are used throughout the process to limit dust created by the rubblization.
 +
 
 +
=== Photos of Equipment ===
 +
 
 +
{| class="wikitable"
 +
|+
 +
|-
 +
| [[File:304-004.png|300px|thumb|center|'''Resonant Frequency Breaker''']] | || [[File:304-006.png|300px|thumb|center|'''Multi-Impact Hammer''']]
 +
|-
 +
| [[File:304-008.png|300px|thumb|center|'''Z-Grid Roller''']]  
 +
|-
 +
|}
  
 
{{top}}
 
{{top}}
  
===Documentation===
+
==[[#PRECONSTRUCTION|PRECONSTRUCTION]]==
 +
Preconstruction meetings are held for the Engineer and Contractor to discuss and understand rubblization requirements, placement of the aggregate filler, and acceptance/payment.
 +
 
 +
Prior to the start of pavement rubblizing, the Inspector should perform the following:
 +
# Review the plans to verify the location of the work.
 +
# Verify a surveyor has provided stakes for the work.
 +
# Review the plans and the Special Provision for Maintenance of Traffic. There may be restrictions or staging requirements for installation of the aggregate. Installation restrictions are typically associated with staging requirements on a project and access to side streets and driveways.
 +
# Verify all materials are approved for use and meet specifications, and verify stockpiled materials are protected from weather and sunlight as required by the specifications and manufacturer recommendations.
 +
# Obtain photographs of material tickets, storage method, and location.
 +
# Verify a full depth sawcut relief joint is at the interface of the rubblization and concrete pavement intended for retention or future rubblization.
 +
# Verify constructed pavement widening or shoulders align with adjacent pavement elevations designated for rubblization, and ensure these areas can adequately support a pavement breaker and maintain traffic if required.
 +
# Check construction of new drainage systems, including outlet endings, is complete and functional. Backfill should be compacted to the existing grade to safeguard the drainage system’s integrity.
 +
# Verify utilities are marked prior to starting rubblizing operations. Be aware of any existing utilities, such as drainage structures, valves, and monument boxes, that are to remain. Caution should be used to prevent damage to utilities during rubblization operations.
 +
# Verify pavement over utilities or pipes with less than 18 inches of granular material cover is removed following the plans or Engineer's directives. Removal boundaries should be extended 3 feet beyond each utility or pipe. The excavated areas should be backfilled with filler aggregate in 6-inch layers and compacted per Engineer's directive before compaction operation of the rubblized pavement. Patching material should be retained until after rubblization.
 +
# Ensure all existing HMA overlays are removed from the pavement prior to breaking operations.
 +
# Hold an onsite meeting with the Contractor to discuss:
 +
#* The construction methods that will be used to complete the work.
 +
#** Discuss how control and vehicular traffic will be kept off the rubblized pavement until paving operations begin.
 +
#* Required traffic control measures, proximity of traffic to the work area, and maintaining driveways during construction.
 +
#* Communication required if impacting residents or businesses during installation.
 +
#** Residents and businesses should be contacted if there will be disruptions to services. Coordination by the Contractor with impacted users may be required if disruption is necessary.
 +
#* Review of local ordinances.
 +
#* Disposal of excavated material and material stockpile locations. The Contractor should provide authorization letters to the Engineer noting material stockpile and disposal locations.
 +
#* Soil erosion and sedimentation control measures that will be utilized to minimize soil erosion and subsequent sedimentation.
 +
#* Methods for securing the site during work operations and at the end of each workday.
 +
 
 +
{{top}}
 +
 
 +
==[[#CONSTRUCTION|CONSTRUCTION]]==
 +
Specialized equipment is used to rubblize the concrete pavement and separate it from reinforcement. Each pass of the breaker shoe must overlap the previous pass by a minimum of 1 inch for resonance frequency breakers. Each pass of a multi-hammer breaker typically completes an entire lane width. Throughout the rubblizing process, it is imperative to ensure the broken pavement does not exceed 10 inches as its greatest dimension. Any large segments of broken concrete pavement exceeding this dimension must either be eliminated or further broken down to achieve a smaller dimension. The Contractor must monitor the condition of the breaker shoe and replace it as necessary when it shows signs of wear. The pavement breakers should operate at a speed of 0 to 3 mph.
 +
 
 +
{| class="wikitable"
 +
|+
 +
|-
 +
| [[File:304-010.png|300px|thumb|center|'''Resonant Frequency Breaker Crushing PCC''']] || [[File:304-011.png|300px|thumb|center|'''Resonant Frequency Breaker Head''']]
 +
|-
 +
| [[File:304-013.png|300px|thumb|center|'''Crushed Pavement Behind Resonant Frequency Breaker Through Patch Material''']] || [[File:304-015.png|300px|thumb|center|'''Multi-Impact Hammer Crushing Existing PCC''']]
 +
|-
 +
| [[file:304-017.jpg|300px|thumb|center|'''Crush Pavement Behind Multi-Impact Hammer''']]
 +
|}
 +
 
 +
 
 +
When exposed reinforcement is encountered, it must be marked, cut off below the surface, and removed. Embedded reinforcement can remain in place.
 +
 
 +
{| class="wikitable"
 +
|+
 +
|-
 +
| [[File:304-019.jpg|300px|thumb|center|'''Delaminated Reinforcement''']] || [[File:304-021.png|300px|thumb|center|'''Exposed Reinforcement''']]
 +
|-
 +
| [[File:304-023.png|300px|thumb|center|'''Reinforcement Removal''']]
 +
|-
 +
|}
 +
 
 +
 
 +
 
 +
If a greatly rubblized area, almost powdery looking, is noticed, there is likely a larger, unbroken material below the surface.
 +
 
 +
Areas not well rubblized by the breakers may require additional breaking effort to reduce the material size to less than 10 inches in the largest dimension. Smaller breakers attached to equipment may be used to further rubblize the pavement.
 +
 
 +
The Contractor should set up a water injection system to prevent large dust clouds that can pose health hazards and safety risks. It is crucial to ensure the drainage system is installed and operational before initiating rubblizing, as this process often leads to water migration into the rubblized material. Consideration must be given to the quantity of water utilized during the rolling process. The Contractor should ascertain the appropriate volume of water units required to assist in the compaction effort without saturating the existing grade.
 +
 
 +
It is imperative that the staging sequence is reviewed and followed as there may be delineated periods for road closure or reopening. Traffic is strictly prohibited on rubblized pavement surfaces preceding HMA paving. Should the need arise to open rubblized pavement to traffic, effective coordination with the paving contractor is essential to lay an HMA course over the rubblized pavement surface, facilitating the safe reopening of traffic flow.
 +
 
 +
Aggregate filler will be used to fill low areas of at least 1 inch in depth to bring the grade to finish plan grade.
 +
 
 +
All joint filler, expansion material, or bituminous patching material should be removed after the breaking operations.
 +
 
 +
=== Compaction ===
 +
The Contractor must provide rollers with a minimum gross weight of 10 tons. Rollers must operate at a speed of no greater than 6 feet per second while in high vibration mode.
 +
The Contractor must make at least two full passes with a Z-grid vibratory roller or a steel drum roller are required. A full pass is considered down and back within the same path. All subsequent passes must be made with a pneumatic-tired or steel drum roller. The final pass prior to HMA placement must be completed by a steel drum roller.
 +
 
 +
After compaction and prior to HMA paving, the Contractor should ensure grade does not vary by ±1 inch using a 10-foot straight edge.
 +
 
 +
[[File:304-025.png|300px|left|thumb|'''Z-Grid Roller Compacting Behind Multi-Impact Hammer''']]
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
  
Inspector’s Daily Reports should be used to report quantities of work completed daily.  The actual width of the pavement and plan width of the pavement should be compared to make sure they agree.  The inspector should note the beginning and end station daily to complete the Inspector’s Daily Report.
 
  
 
{{top}}
 
{{top}}
  
==CONSTRUCTION==
+
==[[#INSPECTION & TESTING|INSPECTION & TESTING]]==
 +
=== Inspection ===
 +
Depth checks should also be performed periodically to ensure the rubblized pavement conforms to the plan thickness.
 +
 
 +
The Inspector should utilize, at a minimum, the following tools to perform the required inspection:
 +
* Measuring wheel
 +
* 100-foot tape measure or longer
 +
* 25-foot tape measure
 +
* Chaining pin
 +
* 6-foot stick ruler
 +
* 4-foot level
 +
* Working plans
 +
* Total Station for documenting grade checks if AMG is used by the Contractor
 +
* String line or laser level if traditional survey stakes are used
 +
* Camera
 +
 
 +
The Inspector should take the following steps during construction:
 +
# Verify rubblization is performed per the specifications.
 +
# Observe all patching material and protruding reinforcement is removed.
 +
# Ensure all grade corrections are completed with HMA, not rubbilzed material.
 +
# Perform quality control checks.
 +
# Observe delivery and placement of the crushed material.
 +
# Perform a moisture test on the aggregate material if payment is based on weight.
 +
# Complete the required daily verification of compaction operations through roller pattern verification.
 +
# Verify all acceptance criteria is met.
 +
 
 +
=== Quality Control Checks ===
 +
During rubblizing operations, the Contractor should perform and document the following QC field checks:
 +
# Establish, demonstrate, and document equipment capabilities, including speed and impact frequency. These specifications may be listed on equipment; if they are not, additional investigation may be needed to locate the information.
 +
# Inspect the rubblized pavement at a rate of 1,500 feet per lane, or as determined by the Engineer, to verify whether the reinforcement has debonded from the concrete pavement, and to determine if rubblized broken down concrete meets acceptable particle size requirements as noted in Subsection 304.03.F of the Standard Specifications for Construction.
 +
#* Excavate a 25-square-foot area to expose the top mat of reinforcement. Notify the Engineer at least 2 hours prior to excavation beginning to allow for verification.
 +
#* If the Engineer directs the Contractor to use manual methods for excavation, tools similar to a shovel or pick should be used. Use a geologist’s pick or mason hammer to separate the broken concrete above the reinforcement mat. The Contractor will remove as much broken concrete material as possible to expose the reinforcement mat. Once the reinforcement mat is exposed, clean it using a stiff bristled broom or brush to fully expose it. MDOT considers a reinforcement mat debonded if at least 80% of the mat is visible after manual excavation and cleaning processes.
 +
#* Once the top mat of reinforcement is exposed, sound the concrete below the mat to determine if the concrete below is fractured.
 +
#* If the spot check fails, further rubblizing will be required with modifications to the Contractor’s operations to meet requirements.
 +
#* Once the spot check is complete, fill in the 25-square-foot area with filler aggregate and compact it.
 +
# Confirm the surface has a consistent rubblized appearance with no unbroken strips of pavement, exposed reinforcement, or visible joint filler and asphalt patching material.
 +
 
 +
[[File:304-027.png|300px|left|thumb|'''Spot Check Area''']]
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
  
  
===Inspection===
 
  
The inspector should study the staging details very carefully.  In situations where the road must be reopened for traffic, the rubblizing Contractor and paving Contractor should coordinate these efforts so any area open to traffic has at least an initial leveling course (scratch course) placed daily.
 
  
Where the existing pavement is composite (HMA over concrete), the inspector should closely monitor the cold-milling operation making sure the existing HMA has been completely milled off.
 
  
Placement of the drainage system (most often Prefabricated Drainage System) should be clarified with the Contractor.  Emphasis should be placed on both grade and outlet.  The roadway typical cross section should specify the grade placement of the drainage system relative to the existing slab.  Outlet placement will be determined by the existing roadway terrain.  It is essential to have the drainage system in place and working prior to rubblizing as the process tends to encourage migration of water into rubblized material.
 
  
The inspector should take care at cross culverts.  The drainage system should be checked for clearance over the culverts.  If no clearance can be obtained over the culverts, the drainage system will need to be interrupted and an outlet will probably need to be placed.
 
  
Particular attention should be paid to the amount of water that is applied in the rolling process. The compaction effort is specified by the Rolling Pattern in the Standard Specifications for Construction. The inspector and Contractor should work together and determine the proper number of water units to apply to aid in the compaction effort, but not saturate the existing grade. The inspector should also pay close attention to the rubblizing making sure there is not excessive oversize material [less than 6 inches (150 mm) is the greatest dimension]. The oversize material will have to be removed or reduced to smaller diameter particles with a jackhammer or similar device.
+
==== Acceptance Criteria ====
 +
Upon observing the Contractor perform quality control checks, the Engineer, or their representative, will verify the following acceptance criteria has been met:
 +
# PCC pavement is entirely disintegrated to the full depth.
 +
# Non-reinforced PCC pavement and concrete pavement patches are reduced to unbound particles with a maximum size of 10 inches. A pneumatic breaker head may be used to reduce oversized particles to meet specification.
 +
# Reinforced PCC pavement and concrete pavement patches are reduced to unbound particles with an average size ranging from 2 to 6 inches.
 +
# Reinforcement is deboned.
 +
# No oversized broken pavement is present at the surface.
 +
# All exposed reinforcement was marked and cut off below the surface and removed, with embedded reinforcement allowed to remain.
 +
# Any joints or cracks wider than 1/4 inch at the surface are filled with aggregate filler.
 +
# There is no displacement of the underlying base, subgrade, and underdrains.
 +
 
 +
=== Testing ===
 +
For evaluation of aggregate materials, use only certified aggregate sampling and testing technicians. Refer to the [https://www.michigan.gov/mdot/-/media/Project/Websites/MDOT/Business/Construction/Standard-Specifications-Construction/CFS-Manuals/Procedures-Aggregate-Inspection.pdf?rev=e2f19aadca344460afca48b7b9ddb31e&hash=5D3CB25E2CD084FACCFD616004CCEB82 Procedures for Aggregate Inspection] manual and project specifications for testing requirements and frequencies. The Engineer should track the approved testing of installed aggregate and coordinate with the respective testing lab to ensure the required number of aggregate tests for the project are being completed.
  
 
{{top}}
 
{{top}}
  
==MEASUREMENT AND PAYMENT==
+
==[[#MEASUREMENT, DOCUMENTATION & PAYMENT|MEASUREMENT, DOCUMENTATION & PAYMENT]]==
 +
=== Measurement and Payment ===
 +
Rubblizing PCC pavement typically involves three pay items.
 +
* Pavt, Rubblize: Paid by area, measured in square yards based on the length and width as measured in the field.
 +
** Rubblizing work.
 +
** Required quality control work.
 +
** Dust suppression, including water application.
 +
** Removal of joint fillers and patching materials.
 +
** Cutting, loading, hauling, and disposing of any exposed steel reinforcement and immediate restoration of disturbed rubblized concrete.
 +
** Breaking down, removing, and disposing of oversized pavement pieces.
 +
** Disposing of material removed from inspection areas.
 +
** Maintaining the condition of rubblized pavement until placement of overlying HMA pavement.
 +
* Aggregate filler: Paid by weight, with the scale weight of the material measured in tons.
 +
** Cost of producing, delivering, placing, leveling, and compacting the aggregate in rubblized pavement areas.
 +
** Moisture content readings must be taken, and if the moisture content exceeds 8%, adjustments to the load ticket will be necessary.
 +
* Sawcut, Rubblize: Paid by linear foot, measured from the start of the sawcut to the end of the sawcut.
 +
** Cost of cutting a relief joint to full depth where the rubblized pavement meets pavement that is required to remain or will be removed for other purposes.
 +
** Cutting the longitudinal joint through the tie bars where necessary.
 +
** Concrete pavement removal will be paid for separately as Pavt, Rem in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=139 Section 204 of the Standard Specifications for Construction].
 +
 
 +
=== Documentation ===
 +
The Daily Work Report (DWR) should show all computations, measurements and supporting documentation needed to verify the quantity submitted for payment. Primary supporting documentation includes moisture, grade, and depth checks.
 +
 
 +
[https://mdotjboss.state.mi.us/webforms/GetDocument.htm?fileName=1900.pdf Form 1900, Aggregate Inspection Daily Report], will need to be completed for every sublot of aggregate to track gradation acceptance.
 +
 
 +
{{top}}
 +
 
 +
==[[#LOCAL AGENCY PROJECTS|LOCAL AGENCY PROJECTS]]==
  
 
<span style="color: red"> -Reserved- </span>
 
<span style="color: red"> -Reserved- </span>
  
 
{{top}}
 
{{top}}
 +
 +
==[[#RAIL PROJECTS|RAIL PROJECTS]]==
 +
 +
<span style="color: red"> -Reserved- </span>
 +
 +
{{top}}
 +
 +
 +
[[Category:Construction Manual]]
 +
[[Category:Division 3]]
 +
[[Category:Section 304]]
 +
[[Category:New CM Format]]

Latest revision as of 12:33, 8 October 2025

304
Rubblizing Portland Cement Concrete Pavement



GENERAL DESCRIPTION

Definitions of Terms

Aggregate Filler: Aggregate filler is additional aggregate required to adjust rubblized pavement to meet specified plan grades.

Portland Cement Concrete (PCC): PCC is a material used within a pavement system as a roadway surface.

Rubblizing: Rubblizing is the process of disintegrating concrete pavement or structures using hydraulic breakers, jackhammers, or specialized machinery to produce rubble suitable as a base course for hot mix asphalt (HMA).

Sawcut, Rubblize: A full-depth relief sawcut between rubblized pavement and pavement areas planned to be retained.

General Overview

Rubblizing PCC pavement is a method employed in road rehabilitation and reconstruction. It entails breaking existing concrete pavement into small, irregular pieces of rubble using specialized machinery like resonant pavement breakers or high-energy impact breakers. This process allows for in-place recycling of existing concrete, providing a suitable base for the construction of a new asphalt overlay. Rubblizing is chosen for its cost-effectiveness, reduced construction time, and minimal disruption to traffic compared to conventional pavement removal methods. It can be used on both reinforced and non-reinforced pavement. For an overview of operations, refer to HMA Paving Operations Video 6 – Rubblizing (youtube.com).

[top of page]


MATERIALS

All materials must meet acceptance requirements in the Materials Source Guide and be listed on the Contractor-provided Material Source Lists in the project files.

Dense-Graded Aggregate (21AA)

If additional material is needed after pavement rubblization, only dense-graded 21AA aggregate is permitted for aggregate filler.

The aggregate must meet the requirements in Section 902 of the Standard Specifications for Construction and the Aggregate Inspection Manual. Aggregate filler can consist of:

  • Limestone
  • Recycled concrete
  • Slag aggregate

Loss by wash should be in accordance with Section 902 of the Standard Specifications for Construction.

Filler Aggregate Placed over Crushed Pavement


[top of page]


EQUIPMENT

The following equipment is typically used for construction of a rubblizing PCC pavement:

  • Resonant frequency breaker
  • Multi-impact hammer
  • Bulldozer
  • Grader
  • Single or dual drum rollers
  • Z-grid roller
  • Pneumatic tire roller
  • Water injection system

Description of Equipment

Rubblizing is performed by either a resonant frequency breaker or a multi-impact hammer. Once the pavement is rubbilized, fine grading is performed with a bulldozer or grader to achieve the correct cross-section. The rubblized pavement is then compacted with a z-grid roller to achieve the required density. Water injection systems are used throughout the process to limit dust created by the rubblization.

Photos of Equipment

Resonant Frequency Breaker
|
Multi-Impact Hammer
Z-Grid Roller

[top of page]


PRECONSTRUCTION

Preconstruction meetings are held for the Engineer and Contractor to discuss and understand rubblization requirements, placement of the aggregate filler, and acceptance/payment.

Prior to the start of pavement rubblizing, the Inspector should perform the following:

  1. Review the plans to verify the location of the work.
  2. Verify a surveyor has provided stakes for the work.
  3. Review the plans and the Special Provision for Maintenance of Traffic. There may be restrictions or staging requirements for installation of the aggregate. Installation restrictions are typically associated with staging requirements on a project and access to side streets and driveways.
  4. Verify all materials are approved for use and meet specifications, and verify stockpiled materials are protected from weather and sunlight as required by the specifications and manufacturer recommendations.
  5. Obtain photographs of material tickets, storage method, and location.
  6. Verify a full depth sawcut relief joint is at the interface of the rubblization and concrete pavement intended for retention or future rubblization.
  7. Verify constructed pavement widening or shoulders align with adjacent pavement elevations designated for rubblization, and ensure these areas can adequately support a pavement breaker and maintain traffic if required.
  8. Check construction of new drainage systems, including outlet endings, is complete and functional. Backfill should be compacted to the existing grade to safeguard the drainage system’s integrity.
  9. Verify utilities are marked prior to starting rubblizing operations. Be aware of any existing utilities, such as drainage structures, valves, and monument boxes, that are to remain. Caution should be used to prevent damage to utilities during rubblization operations.
  10. Verify pavement over utilities or pipes with less than 18 inches of granular material cover is removed following the plans or Engineer's directives. Removal boundaries should be extended 3 feet beyond each utility or pipe. The excavated areas should be backfilled with filler aggregate in 6-inch layers and compacted per Engineer's directive before compaction operation of the rubblized pavement. Patching material should be retained until after rubblization.
  11. Ensure all existing HMA overlays are removed from the pavement prior to breaking operations.
  12. Hold an onsite meeting with the Contractor to discuss:
    • The construction methods that will be used to complete the work.
      • Discuss how control and vehicular traffic will be kept off the rubblized pavement until paving operations begin.
    • Required traffic control measures, proximity of traffic to the work area, and maintaining driveways during construction.
    • Communication required if impacting residents or businesses during installation.
      • Residents and businesses should be contacted if there will be disruptions to services. Coordination by the Contractor with impacted users may be required if disruption is necessary.
    • Review of local ordinances.
    • Disposal of excavated material and material stockpile locations. The Contractor should provide authorization letters to the Engineer noting material stockpile and disposal locations.
    • Soil erosion and sedimentation control measures that will be utilized to minimize soil erosion and subsequent sedimentation.
    • Methods for securing the site during work operations and at the end of each workday.

[top of page]


CONSTRUCTION

Specialized equipment is used to rubblize the concrete pavement and separate it from reinforcement. Each pass of the breaker shoe must overlap the previous pass by a minimum of 1 inch for resonance frequency breakers. Each pass of a multi-hammer breaker typically completes an entire lane width. Throughout the rubblizing process, it is imperative to ensure the broken pavement does not exceed 10 inches as its greatest dimension. Any large segments of broken concrete pavement exceeding this dimension must either be eliminated or further broken down to achieve a smaller dimension. The Contractor must monitor the condition of the breaker shoe and replace it as necessary when it shows signs of wear. The pavement breakers should operate at a speed of 0 to 3 mph.

Resonant Frequency Breaker Crushing PCC
Resonant Frequency Breaker Head
Crushed Pavement Behind Resonant Frequency Breaker Through Patch Material
Multi-Impact Hammer Crushing Existing PCC
Crush Pavement Behind Multi-Impact Hammer


When exposed reinforcement is encountered, it must be marked, cut off below the surface, and removed. Embedded reinforcement can remain in place.

Delaminated Reinforcement
Exposed Reinforcement
Reinforcement Removal


If a greatly rubblized area, almost powdery looking, is noticed, there is likely a larger, unbroken material below the surface.

Areas not well rubblized by the breakers may require additional breaking effort to reduce the material size to less than 10 inches in the largest dimension. Smaller breakers attached to equipment may be used to further rubblize the pavement.

The Contractor should set up a water injection system to prevent large dust clouds that can pose health hazards and safety risks. It is crucial to ensure the drainage system is installed and operational before initiating rubblizing, as this process often leads to water migration into the rubblized material. Consideration must be given to the quantity of water utilized during the rolling process. The Contractor should ascertain the appropriate volume of water units required to assist in the compaction effort without saturating the existing grade.

It is imperative that the staging sequence is reviewed and followed as there may be delineated periods for road closure or reopening. Traffic is strictly prohibited on rubblized pavement surfaces preceding HMA paving. Should the need arise to open rubblized pavement to traffic, effective coordination with the paving contractor is essential to lay an HMA course over the rubblized pavement surface, facilitating the safe reopening of traffic flow.

Aggregate filler will be used to fill low areas of at least 1 inch in depth to bring the grade to finish plan grade.

All joint filler, expansion material, or bituminous patching material should be removed after the breaking operations.

Compaction

The Contractor must provide rollers with a minimum gross weight of 10 tons. Rollers must operate at a speed of no greater than 6 feet per second while in high vibration mode. The Contractor must make at least two full passes with a Z-grid vibratory roller or a steel drum roller are required. A full pass is considered down and back within the same path. All subsequent passes must be made with a pneumatic-tired or steel drum roller. The final pass prior to HMA placement must be completed by a steel drum roller.

After compaction and prior to HMA paving, the Contractor should ensure grade does not vary by ±1 inch using a 10-foot straight edge.

Z-Grid Roller Compacting Behind Multi-Impact Hammer










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INSPECTION & TESTING

Inspection

Depth checks should also be performed periodically to ensure the rubblized pavement conforms to the plan thickness.

The Inspector should utilize, at a minimum, the following tools to perform the required inspection:

  • Measuring wheel
  • 100-foot tape measure or longer
  • 25-foot tape measure
  • Chaining pin
  • 6-foot stick ruler
  • 4-foot level
  • Working plans
  • Total Station for documenting grade checks if AMG is used by the Contractor
  • String line or laser level if traditional survey stakes are used
  • Camera

The Inspector should take the following steps during construction:

  1. Verify rubblization is performed per the specifications.
  2. Observe all patching material and protruding reinforcement is removed.
  3. Ensure all grade corrections are completed with HMA, not rubbilzed material.
  4. Perform quality control checks.
  5. Observe delivery and placement of the crushed material.
  6. Perform a moisture test on the aggregate material if payment is based on weight.
  7. Complete the required daily verification of compaction operations through roller pattern verification.
  8. Verify all acceptance criteria is met.

Quality Control Checks

During rubblizing operations, the Contractor should perform and document the following QC field checks:

  1. Establish, demonstrate, and document equipment capabilities, including speed and impact frequency. These specifications may be listed on equipment; if they are not, additional investigation may be needed to locate the information.
  2. Inspect the rubblized pavement at a rate of 1,500 feet per lane, or as determined by the Engineer, to verify whether the reinforcement has debonded from the concrete pavement, and to determine if rubblized broken down concrete meets acceptable particle size requirements as noted in Subsection 304.03.F of the Standard Specifications for Construction.
    • Excavate a 25-square-foot area to expose the top mat of reinforcement. Notify the Engineer at least 2 hours prior to excavation beginning to allow for verification.
    • If the Engineer directs the Contractor to use manual methods for excavation, tools similar to a shovel or pick should be used. Use a geologist’s pick or mason hammer to separate the broken concrete above the reinforcement mat. The Contractor will remove as much broken concrete material as possible to expose the reinforcement mat. Once the reinforcement mat is exposed, clean it using a stiff bristled broom or brush to fully expose it. MDOT considers a reinforcement mat debonded if at least 80% of the mat is visible after manual excavation and cleaning processes.
    • Once the top mat of reinforcement is exposed, sound the concrete below the mat to determine if the concrete below is fractured.
    • If the spot check fails, further rubblizing will be required with modifications to the Contractor’s operations to meet requirements.
    • Once the spot check is complete, fill in the 25-square-foot area with filler aggregate and compact it.
  3. Confirm the surface has a consistent rubblized appearance with no unbroken strips of pavement, exposed reinforcement, or visible joint filler and asphalt patching material.
Spot Check Area










Acceptance Criteria

Upon observing the Contractor perform quality control checks, the Engineer, or their representative, will verify the following acceptance criteria has been met:

  1. PCC pavement is entirely disintegrated to the full depth.
  2. Non-reinforced PCC pavement and concrete pavement patches are reduced to unbound particles with a maximum size of 10 inches. A pneumatic breaker head may be used to reduce oversized particles to meet specification.
  3. Reinforced PCC pavement and concrete pavement patches are reduced to unbound particles with an average size ranging from 2 to 6 inches.
  4. Reinforcement is deboned.
  5. No oversized broken pavement is present at the surface.
  6. All exposed reinforcement was marked and cut off below the surface and removed, with embedded reinforcement allowed to remain.
  7. Any joints or cracks wider than 1/4 inch at the surface are filled with aggregate filler.
  8. There is no displacement of the underlying base, subgrade, and underdrains.

Testing

For evaluation of aggregate materials, use only certified aggregate sampling and testing technicians. Refer to the Procedures for Aggregate Inspection manual and project specifications for testing requirements and frequencies. The Engineer should track the approved testing of installed aggregate and coordinate with the respective testing lab to ensure the required number of aggregate tests for the project are being completed.

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MEASUREMENT, DOCUMENTATION & PAYMENT

Measurement and Payment

Rubblizing PCC pavement typically involves three pay items.

  • Pavt, Rubblize: Paid by area, measured in square yards based on the length and width as measured in the field.
    • Rubblizing work.
    • Required quality control work.
    • Dust suppression, including water application.
    • Removal of joint fillers and patching materials.
    • Cutting, loading, hauling, and disposing of any exposed steel reinforcement and immediate restoration of disturbed rubblized concrete.
    • Breaking down, removing, and disposing of oversized pavement pieces.
    • Disposing of material removed from inspection areas.
    • Maintaining the condition of rubblized pavement until placement of overlying HMA pavement.
  • Aggregate filler: Paid by weight, with the scale weight of the material measured in tons.
    • Cost of producing, delivering, placing, leveling, and compacting the aggregate in rubblized pavement areas.
    • Moisture content readings must be taken, and if the moisture content exceeds 8%, adjustments to the load ticket will be necessary.
  • Sawcut, Rubblize: Paid by linear foot, measured from the start of the sawcut to the end of the sawcut.
    • Cost of cutting a relief joint to full depth where the rubblized pavement meets pavement that is required to remain or will be removed for other purposes.
    • Cutting the longitudinal joint through the tie bars where necessary.
    • Concrete pavement removal will be paid for separately as Pavt, Rem in accordance with Section 204 of the Standard Specifications for Construction.

Documentation

The Daily Work Report (DWR) should show all computations, measurements and supporting documentation needed to verify the quantity submitted for payment. Primary supporting documentation includes moisture, grade, and depth checks.

Form 1900, Aggregate Inspection Daily Report, will need to be completed for every sublot of aggregate to track gradation acceptance.

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LOCAL AGENCY PROJECTS

-Reserved-

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RAIL PROJECTS

-Reserved-

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