Difference between revisions of "602 - Concrete Pavement Construction"

From MediaWiki
Jump to navigation Jump to search
Line 82: Line 82:
  
 
==[[#CONSTRUCTION|CONSTRUCTION]]==
 
==[[#CONSTRUCTION|CONSTRUCTION]]==
 
  
 
===[[#Concrete Testing Procedures|Concrete Testing Procedures]]===
 
===[[#Concrete Testing Procedures|Concrete Testing Procedures]]===
  
 
Quality control and Quality Assurance  testing for concrete  will be in accordance with  Special provision 12SP604(B).  
 
Quality control and Quality Assurance  testing for concrete  will be in accordance with  Special provision 12SP604(B).  
 +
 +
{{top}}
 +
 +
===[[#PLACING AND FINISHING CONCRETE|PLACING AND FINISHING CONCRETE]]===
 +
 +
The specifications set forth the equipment requirements necessary in the paving train.  The specific equipment requirements have been greatly reduced during recent years.  We are less concerned about the specific type or piece of equipment the Contractor uses and more concerned with the result.  The inspector should note the trimming, placing, spreading, consolidation, finishing, texturing and curing equipment the Contractor plans to use to see if it fits the project on which it will be used.  Equipment capacity and capability will not be the same on a small urban widening project as on a high production rural project.  The Lansing Office concrete staff inspector will visit the project when paving starts to assist in determining equipment suitability and other related problems to get the project properly started.  If there are questions about the condition and/or equipment capability, contact the Engineer.
 +
{{top}}
 +
====[[#Minimum Project Requirements|Minimum Project Requirements]]====
 +
 +
* Some method of trimming the base.
 +
* A method of delivering and placing the concrete on the grade in a timely manner, without segregation.
 +
* Installing lane ties, if needed.
 +
* Consolidating and finishing the concrete, straight dging and floating.
 +
* Edging and texturing the surface.
 +
* Curing the pavement.
 +
* Sawing and sealing the joints.
 +
 +
Screeds and pan floats must be checked for proper slope adjustment.
 +
 +
The inspector should verify that the membrane sprayer is in working condition before paving starts.  If in doubt, the Contractor should demonstrate this capability.
 +
 +
Check to see that the Contractor has all the necessary hand tools, such as 5 foot (1.5 m) and 10 foot (3 m) straightedges, floats, edgers and stencils.
 +
 +
If forms are used, they should be checked for straightness, general condition, condition of locks, etc. before form setting operations begin.  These forms serve the dual purpose of containing the plastic concrete and providing a track on which most of the concrete placing and finishing equipment rides.  For radii of 150 feet (45 m) or less, flexible forms will be required (see [http://mdotcf.state.mi.us/public/specbook/files/2012/602%20Conc%20Pavt%20Construction.pdf subsection 602.03] of the Standard Specifications for Construction).  Review the specifications and checklist, included in this manual, for specific form and backup rail requirements.
 +
{{top}}
 +
 +
====[[#Grade Condition|Grade Condition]]====
 +
 +
After the aggregate base or open-graded drainage course (OGDC) is placed, shaped and compacted, it is brought to final grade, usually by an automatic trimmer.  This machine operates off a string line for line and grade.  The string line should be checked for sags before the final cut on the aggregate base, as most slipform paving equipment runs on the aggregate base for final grade.
 +
 +
{{top}}
 +
 +
====[[#Aggregate Base|Aggregate Base]]====
 +
 +
* Behind the grading operation, the aggregate base should be checked for thickness, elevation and proper cross section.
 +
* Thickness is checked by digging through the aggregate and recording the depth of the hole.
 +
* Depth should be within 3/4 inch (15 mm) of plan thickness (example: a minimum of 31/4 inch (85 mm) when 4 inches (100 mm) depth is specified).
 +
* Elevation and cross section are determined by stretching a string line across the grade from stakes set by the instrument crew.
 +
* Measurements are made from the string line to the grade and recorded.
 +
* Any significant variations from the plan should be brought to the Engineer’s and Contractor’s attention.
 +
* Any areas where the grade appears to have been disturbed should be rechecked.
 +
* The grade should be moist when paving operations start, but there should be no puddles of standing water.
 +
 +
{{top}}
 +
 +
====[[#Load Transfer Assemblies|Load Transfer Assemblies]]====
 +
 +
After the base is properly compacted and fine trimmed to receive the concrete load, transfer assemblies are placed at joint locations.  The inspector should work closely with the Contractor’s crew while they are setting these assemblies.
 +
 +
The assembly itself holds the dowel bars in position so they will not move during concrete placement and consolidation.
 +
 +
* The distance between joints should be checked.
 +
* The assemblies must be positioned at right angles to the centerline as shown in Figure 602-5.
 +
* After they are properly positioned, they must be staked to the base using six pins per basket assembly.
 +
* The basket pin must be in contact with the lower horizontal wire as shown in Figure 602-6.
 +
 +
After the Contractor completes staking the assembly, the inspector should check vertical alignment with the basket level to ensure that dowels are parallel with the pavement surface (Figure 602-6).
 +
 +
At this time, the bars should be visually checked for horizontal alignment by sighting over the tops of the bars to the previously set assemblies to see if the bars are parallel to the string line.
 +
 +
Even though the assemblies have been set at right angles to the string line, the bars may not be parallel to the string line due to improper fabrication of the assemblies.
 +
 +
Any apparent misalignment can usually be corrected by tapping the frame to realign the bars.
 +
 +
The bars should also be inspected for complete coating on at least two-thirds of the length of the bar.
  
 
{{top}}
 
{{top}}

Revision as of 12:34, 19 March 2014

602
Concrete Pavement Construction
2012 STANDARD SPECIFICATIONS FOR CONSTRUCTION - SECTION 602


GENERAL

-Reserved-

[top of page]


MATERIALS

Acceptance of Materials

Before paving operations start, the paving inspector should verify that all materials that need to be incorporated in the pavement have been tested and accepted. Most materials will be stockpiled in the Contractor’s yard on the project site. Often this is also the location of the batching plant.

General Materials Inspection
1

When the load transfer assemblies arrive on the project site, call Region materials personnel so they can verify that the assemblies were built according to the standard plans. Notice of acceptance by Region materials personnel is the required documentation.

2

Check to see if the dowel bars and the fiber joint filler material are certified. Sampling and testing may be required.

3

After the Contractor starts to set the load transfer assemblies on the grade, they must be visually inspected for:

  • Broken or missing welds.
  • Damage in handling or shipping.
  • Proper height of dowel bars in the assembly.
  • Proper height and length of fiber joint filler.
  • Dowels must match holes in fiber joint filler with no space for mortar leakage through fiber joint filler.
  • Compliance of expansion caps.
4

The entire bar is to be coated with an approved epoxy coating to prevent corrosion, and the entire bar’s length is to be coated with an approved material to prevent concrete from adhering to the bar.

5

Any material of uncertain origin should be piled separately and not used until it is determined that it meets specification requirements.

6

Visually inspect the handling and storage of all materials used in the concrete paving operation.


[top of page]


Tie Bars and Bent Bars

These items should be checked for certification, or sampled and tested when they arrive on a project.

[top of page]


Curing Compound

  • Check certification, or sample and test each batch or lot.
  • Material may be in drums or in a large tank. Inspection consists of seeing that the material is not contaminated or diluted and that it is mixed according to the manufacturer’s recommendations.
  • A curing compound should not be used when stored from one construction season to the next without resampling and testing.
  • Check yield of material to ensure correct coverage.

[top of page]


CONSTRUCTION

Concrete Testing Procedures

Quality control and Quality Assurance testing for concrete will be in accordance with Special provision 12SP604(B).

[top of page]


PLACING AND FINISHING CONCRETE

The specifications set forth the equipment requirements necessary in the paving train. The specific equipment requirements have been greatly reduced during recent years. We are less concerned about the specific type or piece of equipment the Contractor uses and more concerned with the result. The inspector should note the trimming, placing, spreading, consolidation, finishing, texturing and curing equipment the Contractor plans to use to see if it fits the project on which it will be used. Equipment capacity and capability will not be the same on a small urban widening project as on a high production rural project. The Lansing Office concrete staff inspector will visit the project when paving starts to assist in determining equipment suitability and other related problems to get the project properly started. If there are questions about the condition and/or equipment capability, contact the Engineer.

[top of page]


Minimum Project Requirements

  • Some method of trimming the base.
  • A method of delivering and placing the concrete on the grade in a timely manner, without segregation.
  • Installing lane ties, if needed.
  • Consolidating and finishing the concrete, straight dging and floating.
  • Edging and texturing the surface.
  • Curing the pavement.
  • Sawing and sealing the joints.

Screeds and pan floats must be checked for proper slope adjustment.

The inspector should verify that the membrane sprayer is in working condition before paving starts. If in doubt, the Contractor should demonstrate this capability.

Check to see that the Contractor has all the necessary hand tools, such as 5 foot (1.5 m) and 10 foot (3 m) straightedges, floats, edgers and stencils.

If forms are used, they should be checked for straightness, general condition, condition of locks, etc. before form setting operations begin. These forms serve the dual purpose of containing the plastic concrete and providing a track on which most of the concrete placing and finishing equipment rides. For radii of 150 feet (45 m) or less, flexible forms will be required (see subsection 602.03 of the Standard Specifications for Construction). Review the specifications and checklist, included in this manual, for specific form and backup rail requirements.

[top of page]


Grade Condition

After the aggregate base or open-graded drainage course (OGDC) is placed, shaped and compacted, it is brought to final grade, usually by an automatic trimmer. This machine operates off a string line for line and grade. The string line should be checked for sags before the final cut on the aggregate base, as most slipform paving equipment runs on the aggregate base for final grade.

[top of page]


Aggregate Base

  • Behind the grading operation, the aggregate base should be checked for thickness, elevation and proper cross section.
  • Thickness is checked by digging through the aggregate and recording the depth of the hole.
  • Depth should be within 3/4 inch (15 mm) of plan thickness (example: a minimum of 31/4 inch (85 mm) when 4 inches (100 mm) depth is specified).
  • Elevation and cross section are determined by stretching a string line across the grade from stakes set by the instrument crew.
  • Measurements are made from the string line to the grade and recorded.
  • Any significant variations from the plan should be brought to the Engineer’s and Contractor’s attention.
  • Any areas where the grade appears to have been disturbed should be rechecked.
  • The grade should be moist when paving operations start, but there should be no puddles of standing water.

[top of page]


Load Transfer Assemblies

After the base is properly compacted and fine trimmed to receive the concrete load, transfer assemblies are placed at joint locations. The inspector should work closely with the Contractor’s crew while they are setting these assemblies.

The assembly itself holds the dowel bars in position so they will not move during concrete placement and consolidation.

  • The distance between joints should be checked.
  • The assemblies must be positioned at right angles to the centerline as shown in Figure 602-5.
  • After they are properly positioned, they must be staked to the base using six pins per basket assembly.
  • The basket pin must be in contact with the lower horizontal wire as shown in Figure 602-6.

After the Contractor completes staking the assembly, the inspector should check vertical alignment with the basket level to ensure that dowels are parallel with the pavement surface (Figure 602-6).

At this time, the bars should be visually checked for horizontal alignment by sighting over the tops of the bars to the previously set assemblies to see if the bars are parallel to the string line.

Even though the assemblies have been set at right angles to the string line, the bars may not be parallel to the string line due to improper fabrication of the assemblies.

Any apparent misalignment can usually be corrected by tapping the frame to realign the bars.

The bars should also be inspected for complete coating on at least two-thirds of the length of the bar.

[top of page]


MEASUREMENT AND PAYMENT

Pavement Coring

To determine pavement, shoulder and base course thickness and depth of reinforcement, cores shall be taken from the pavement before its final acceptance to determine the thickness of the pavement and depth of pavement reinforcement below the pavement surface according to MTM 201. Refer to subsection 602.04 of the Standard Specifications for Construction and the following flow chart (see Figure 602-9) for this determination.

Figure 602-9 - Pavement Coring for Acceptance Flow Chart

[top of page]


Ride Quality

A specification to encourage the Contractor’s to construct the smoothest pavements possible and the method to measure the surface for smoothness.

The Contractors may use a California-type Profilograph or a GM-type Rapid Travel Profilometer to measure the pavement smoothness.

The Engineer will establish and mark the limits for Ride Quality Measurement including the POB, POE and any excluded areas.

The California-type Profilograph will produce a trace, or Profilogram, on graph paper, to a true 1:300 horizontal scale and true 1:1 vertical scale, which will be analyzed according to Michigan Test Method 204-88.

If a computerized Profilograph is used, a trace will not need to be analyzed, but should be spot checked with a blanking band.

The equipment must be calibrated before use.

Tire pressure should be 25.375 psi ± 1.015 psi (175 kPa ± 7 kPa) in the recording wheel.

The horizontal calibration will be checked by running the Profilograph over a measured 1000 foot (300 m) length which should produce a trace of 3.28 ft ± 0.118 in (1 m ± 3 mm). Calibration of the computerized version will be run over a distance of 1000 foot (300 m) and should produce a printout within ± 3.28 feet (1 m).

The vertical calibration is to be done according to the manufacturer’s specification and must be documented by the Contractor.

The GM-type Profilometer will be calibrated according to the user’s manual.

Software is provided which allows the operator to test the operation of the three buttons and computer system, along with a “bounce” test.

The vertical calibration of the laser sensor is to be done according to the manufacturer’s specification and must be documented by the Contractor.

The horizontal distance is calibrated by traveling a known distance and typing in the value on the keyboard while in the calibration mode. The continued reliability of the odometer will depend on a constant tire pressure.

The measurement/profile will be taken in the wheel tracks of each lane.

The starting position of Ride Quality using the California-type Profilograph is when the rear wheel assembly is entirely on the road surface, placing the recording wheel 16.25 feet (5 m) beyond the POB. The ending position will be when the front wheel assembly is at the POE, placing the recording wheel 16.25 feet (5 m) short of the POE. Whenever the run is stopped before the POE, the recording wheel should be placed at the same location for a restart. See Figure 602-10 for a Profilograph.

Measurement outside the POB or POE may be done to check for bumps, and will be paid as Ride Quality Measurement - Concrete.

The software for the GM-type Profilometer has been designed to simulate the same starting and ending points as the California Profilograph. Starting the measurement (GO button) at the POB will start data recording at 16.25 foot (5 m) after the POB. Ending the run (STOP button) at the POE will stop the data recording 16.25 foot (5 m) prior to the POE. Caution should be taken when stopping the GM Profilometer between the POB and POE as in daily or short runs. As the recording data will stop 16.25 foot (5 m) prior pushing the Stop button, the next run will have to be started 32.5 foot (10 m) before that same point to start the data recording at the right point. See Figure 602-11 for an example of starting and stopping points.

The California Profilograph trace will have to be reduced, using a blanking band, to segments. Bumps which exceed the limits established by Special Provision can be located by using a bump template. The computer version will analyze the ride quality and locate the bumps which must be ground.

The rapid travel Profilometer can give data in inches per mile or by a ride quality index, along with the locations of must-grind areas.

Check the proposal for pay items and adjustment table for the item of Ride Quality.

Roadways, collector distributors, ramps and turn lanes that are not covered under a ride quality specification should be evaluated for smoothness and removable bumps in one of three ways:

By using a 10 foot (3 m) straightedge as per MTM 722-97.

By using a rolling straightedge available from the Construction and Technology equipment shop.

By using the rapid travel profilometer, which is programmed to check for bumps according to the Standard Specification for these areas. Contact the Construction Services section for use of this equipment.

Figure 602-10 - Profilograph
Figure 602-11 - Profilograph Starting and Stopping Points

[top of page]