Difference between revisions of "603 - Concrete Pavement Restoration"
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Revision as of 10:13, 29 April 2014
This work consists of repairing portions of a concrete pavement with Portland cement concrete and the type of joints specified. Pavement includes mainline pavement, base course or concrete shoulders.
Tied repair grouted
Contraction repair grouted
Expansion repair grouted
Expansion curb joint
Joint, Tied, Special
Before patching begins, the Engineer and the inspector should review the following items:
- Special Provisions
- Supplemental Specifications
- Project plans and drawings
- Standard Plans
- Standard Specifications
- Concrete pavement condition survey or project log
- Layout patches
- Various joints
- Placing and finishing concrete
- Sealing joints
- Shoulder or curb replacement
Before patching begins, the inspector should verify that proper concrete mix design charts are being used and that all materials to be incorporated in the patches have been tested and accepted.
Concrete for patching must be produced by a NRMCA-certified plant, or have been accepted for use by the Region materials personnel as a noncertified, automated or manual plant.
The grade of concrete required is based on the time allowed between the casting of the repair and the intended opening of the repair to traffic.
Unless modified by special provision the grade of concrete required will be as follows.
Type P-NC concrete utilizing a Type C or Type E (non-chloride) set accelerator is the preferred patching mixture for use on MDOT projects. Use the manufacturer’s requirements for these set accelerators with the specified cement content to achieve a minimum flexural strength of 300 psi within the contract open-to-traffic time as determined for the project.
Pavement reinforcement is accepted for use by laboratory testing. The reinforcement should be stored off the ground. If contaminated, the reinforcement must be cleaned thoroughly before use.
Load transfer assemblies for contraction (Cp) and expansion (E2) joints will be according to the Standard Plan R-39 and R-40 Series.
After the assemblies arrive on the project site, they must be visually inspected for the following items.
- Broken or missing welds or bent assemblies
- Proper height of dowels and joint filler for the pavement being repaired
- Holes in joint filler must match the dowel size with no space for leakage
- Use of approved expansion caps and their proper installation
- Verify tie wire of maximum nominal diameter of 0.177 in.
Deformed dowel bars for Trg joints will be epoxy coated, #9 x 18 inches long. Dowel bars for Crg and Erg joints will be epoxy coated, #10 x 18 inches long. Lane tie bars will be straight #5 deformed bars x 18 inches long.
The material used to secure in the dowel bars must be from the Qualified Products List.
The bond breaker used on the dowel bar assembly must be from the Qualified Products List. The bond breaker used for individually placed dowel bars may also be RC 250.
The location of repairs will be listed on a log in the proposal, on the plans, or in the pavement condition survey log.
Locate, number and record, for future documentation, the size and type of joint or the repairs to be removed. The minimum concrete pavement patch length is 4 feet. However, additional patch length is recommended in faulted pavement scenarios. If additional length is needed for proper repair, the inspector should inform the Contractor of the new size after checking with the Engineer.
The Contractor will lay out the patch at right angles to the centerline before sawing starts. Check the Standard Plan R-44 Series for the sawing diagram.
Before removal, the concrete will be sawed full depth according to the details shown on the plans or in the proposal. This must be done with multiple passes within the same 12 hour period or in one pass. Transverse saw cuts will be made in a straight line at right angles to the pavement’s centerline, within a tolerance of 1 inch per lane width. The longitudinal joint adjacent to other lanes, ramps, shoulders, curb and gutter will be sawed full depth.
The pavement surface will be flushed immediately after the sawing operation to remove all slurry. Remove concrete pavement between narrowly spaced sawcuts at the end of the slab with air hammers and hand tools to minimize spalling.
Patches less than 100 feet in length will be removed without disturbing the subbase/subgrade according to subsection 603.03 of the Standard Specifications for Construction.
Repair isolated spalls of 10 in2 and greater per Standard Specification 602.03.P.1.
Intermediate saw cuts, used to reduce slab size more than 6 feet for hauling, should be recorded for payment purposes. Curb sections removed with a patch will be recast with the pour and paid as concrete pavement repair.
After removing the old slab, cleaning up loose material should be done by hand so as not to disturb the existing base. If the existing base was more than 2 inches low before removal, corrections can be made by adding aggregate base material and compacting.
If the existing base is less than 2 inches low, additional aggregate base material is not necessary, and the void will be filled with concrete included in the concrete patching pay item.
Any low base caused by the Contractor’s operation will be filled with concrete at the Contractor’s expense.
According to Standard Plan R-44 Series, place Contraction Joint (Crg) or Expansion Joint (Erg) at transverse joints where the repair meets existing pavement. Tied Joint (Trg) may be permitted as needed.
The same type of joint should be used in the second and third pours, if needed.
Care should be taken to place enough expansion joints (Erg) for the pavement being repaired. Expansion requirements will vary based on condition of existing pavement and temperature at time of repair.
Erg joints should be used only if the repair extends across the entire width of the roadway. If only one lane is being repaired, every effort should be made to match the joint in the original slab.
Transverse joints in pavement, shoulders and curb repairs will be the type shown on the plans. Where existing curbs are to be left in place and expansion space is provided in the adjacent lane repair, an expansion joint (Esc) will be constructed in the curb by sawing and chipping out the existing concrete. It is important that the width of the joint be equal to the width of the joint in the adjacent lane repair. The Esc joint will align with the expansion joint in the repair. The expansion joint filler will be shaped to fit the existing curb cross section.
Expansion joint filler, for the Erg joints, will be 1 inch wide and extend the full depth of the patch minus 1-1/2 inch. Holes drilled into the joint filler must fit snugly around the dowel bars. After October 15, the joint filler will extend the full depth of the patch until the joint is to be sealed. At that time, the top 1-1/2 inch of the filler will be removed to form the joint reservoir for sealing.
Care must be taken to ensure that the holes drilled into the existing slab for dowel bars are true to the horizontal and vertical planes of the roadway. Dowels not in alignment will restrict the Crg or Erg joints from working properly. Some adjustment may be needed in the drilling machine for proper alignment of the dowel bars, or to ensure that the holes miss the reinforcement steel in the existing pavement.
For long one lane repairs spanning an existing joint, Cp or E2 joints should be constructed according to the Standard Plan R-44 Series.
Where more than one lane is cast in a single pour, longitudinal joints will be constructed in line with existing longitudinal joints and to a depth of one-third the thickness of the pavement, either by sawing or by forming. Lane ties will be according to the Standard Plan R-44 Series.
It is important that all holes are cleaned of the drilling residue by using an air wand fully inserted into the hole. Enough grout is placed into the hole to completely fill the space between the bar and the hole. The bars will be inserted slowly with a twisting motion until they are seated properly. Wipe the excess grout off the face of the existing pavement.
The portion of the dowel bars for Crg and Erg joints that extend beyond the face of the existing pavement will be uniformly coated with an approved bond breaker. An approved expansion cap will then be properly installed on each dowel for Erg joints, making sure the cap is not pushed past the 1 inch stops. Deformed bars used in Trg joints and lane ties need not be coated with a bond breaker.
Prior to concrete placement, the inspector should confirm that the epoxy on grout has properly set. This is usually accomplished by obtaining a properly mixed sample, observing the set and the time required to reach set.
Lumber used for forms on the shoulder side of the repair will be nominal 2 inch width and full depth and in one piece for repairs 10 feet or less in length. For repairs greater than 10 feet, wood or metal forms can be used since they can be locked or spliced to provide a continuous form. Form material between lanes can be nominal 1 inch lumber. Care should be taken to reestablish the grade between patch edges for a good ride.
Occasionally, the existing shoulder is in good shape, sound and flush with the edge of the pavement; and with care in removing the old pavement, it could be used as the side form. If the Engineer feels that the existing shoulder can be left, the Contractor must saw between the shoulder and the old slab to eliminate any breakup of the shoulder during removal. If there is any breakup, or after the removal of the slab the shoulder does not form a vertical, continuous edge to finish to, a side form will be required.
Concrete will be placed usually the same day the existing concrete is removed and cast full depth in a single pour.
Immediately before placement of concrete, the existing pavement faces and the base will be dampened. Standing water must be removed before concrete placement.
For repairs more than 15 feet in length, the repair area in adjacent lanes, ramps, or shoulders will be cast separately.
The concrete should be struck off using two passes with a vibrating screed or roller screed. Check the surface with a straightedge. Care in edging, especially along the joint edges, will reduce spalling when forming materials are removed. Any spalling of the joint must be repaired.
For repairs 15 feet or less in length, the screed will be placed parallel to the centerline of the roadway. More than 15 feet in length, the screed will be placed perpendicular to the centerline of the roadway.
An immersion-type vibrator is required for consolidation of the concrete, with special attention given to the area around the dowel bars. The vibrator should be placed in the concrete in a vertical position for best consolidation.
The concrete surface will be struck off twice with a vibratory screed. For repairs 15 feet or less in length, the screed will be placed parallel to the centerline of the roadway. For repairs more than 15 feet in length, the screed will be placed perpendicular to the centerline of the roadway.
While the concrete is still plastic, the surface will be straightedged as follows.
For repairs 10 feet or less in length, the straightedging will be done by placing the straightedge parallel to the pavement centerline with the ends resting on the existing pavement and drawing the straightedge across the repair. The straightedging of 6 feet, 8 feet, and 10 feet repairs will be accomplished by use of a straightedge not exceeding the length of the repair by more than 6 inches. The straightedge will be in contact with the existing pavement while drawing it across the repair. Any high or low spots exceeding 1/8 inch will be corrected. Recheck after corrections are made.
For repairs more than 10 feet in length, the first and last measurement will be made with approximately half the straightedge resting on the existing pavement; and the second and next to last measurement will each be made with 2 inches to 3 inches of the straightedge resting on the existing pavement. Any irregularities will be treated as above.
The surface of the repair should have a texture similar to the adjacent pavement.
The month and the year will be stenciled in each repair. If the existing stationing is removed within the patch area, the station will be restenciled in the repair at the appropriate location. If a Swiss hammer is being used for strength testing, a small area in each corner should be troweled smooth.
Curing compound will be applied immediately after all free water has evaporated from the surface. White membrane curing compound will be used, unless the repair is to be overlaid with HMA, and then transparent curing compound will be used. Either type of curing compound will be applied in 2 coats at a rate of not less than 1 gallon per 25 yd² for each coat.
Insulated blankets having a minimum thickness of 2 inches will be placed over the repaired area when the curing compound has been applied and when the air temperature during the curing period falls below 50°F for all concrete repairs. Edges and seams in the blanket will be secured to prevent loss of heat. Test beams, for open to traffic strengths, will be cured the same as the repair. Insulated blankets may be removed when the concrete has attained a flexural strength of 300 psi for P-NC concrete and 550 psi for P1 and P1M concrete.
The concrete repairs may be opened to traffic when the concrete has attained a flexural strength of 500 psi (3.5 MPa) for repairs constructed with Type P-MS or P-NC concrete, and 550 psi (3.8 MPa) for repairs constructed with Grade HE of Grade PI concrete. Traffic may be allowed over the repair before cleaning and sealing the joints.
Strength test beams, for acceptance and open to traffic, should be made on the job and cured the same as the repairs. This includes being placed under the blankets if blankets are used as an aid to curing.
Beams should be cast at the start of the pour and broken at different times to establish the length of curing time necessary to reach the required strength. Increasing or decreasing the time between making and testing the beams will give the inspector a good indication of the time needed to achieve the required strength.
When using a high early (HE) concrete mixture, beams can be tested at the end of 72 hours and checked against the strength specification. Medium-set (P-MS) or non-chloride (P-NC) concrete should meet specified strengths within 24 hours curing time up to ± 8 hours. The first beam would be tested in ± 4 hours; if it does not meet the specified strength, a second beam would be cured additional time, ± 5 hours, and likewise for a third beam.
If a Swiss hammer is going to be used as an indicator of in-place strength of the patch, before the first beam is unmolded and tested, take 16 readings with the Swiss hammer for calibration.
When the specified strengths are achieved, the inspector should have the approximate cure time and a Swiss hammer number to be used on the repairs for opening to traffic.
The Swiss hammer should be recalibrated with a new set of beams weekly, or any time the mix is changed.
Longitudinal bulkhead joints, joints in base course repairs, joints in repairs constructed in preparation for HMA overlays and Trg joints need not be constructed with joint reservoirs and need not be sealed. All other joints and all saw cuts that were made in pavements, shoulders or gutters over cutting will be cleaned and then sealed with hot poured sealant.
All concrete remaining on top of the expansion joint filler will be removed before abrasive blast cleaning. All joints to be sealed will be abrasive blast cleaned and then cleaned with a jet of compressed air, free of oil and water, having a minimum pressure of 90 psi (620 kPa), immediately before sealing. A bond breaker tape will be placed in the bottom of the Crg joint groove after the final cleaning and before sealing.
Before opening to traffic, HMA shoulders will be restored to the existing line and grade using a plant-mixed HMA mixture, as directed by the Engineer. Cold patch mixtures used for temporary patching will be replaced with plant-mixed HMA mixtures, unless shoulder reconstruction is a part of the project and has not been completed. The HMA mixture will be compacted by mechanical or hand methods suitable for the size hole being filled. HMA plant mixtures will be placed at a temperature suitable for compaction. Concrete shoulders will be constructed as shown on the plans. Materials removed from the shoulder will be disposed of by the Contractor.
Diamond grinding is used to restore the surface longitudinal profile and improved ride quality of a PCC pavement. And many times is done in conjunction with other PCC pavement restoration treatments. Grinding is performed on the roadbed in the longitudinal direction for the entire lane width as specified on the plans.
A self-propelled grinding machine uses diamond saw blades that are gang-mounted on a cutting head to profile the pavement. The machine used can significantly affect the efficiency and rate of grinding. The three most important machine related factors in the diamond grinding process is the weight of the machine, the horse power available to the grinding head, and the grinding head itself. The degree of hardness of the aggregate in the PCC will also affect time required to complete the project.
Usually 54 to 59 blades per foot are required to produce a level surface with a corduroy-type texture. The peaks and ridges of the corduroy should average 1/8 inch. If the area ground results in a polished surface or a surface with fins more, that 1/4 inch high, the spacing of the blades should be adjusted. Grinding equipment that causes ravels, aggregate fractures, spalls or distress of the transverse or longitudinal joint should not be permitted.
The transition between ground and unground pavements should be gradual and result in an acceptable ride quality. Care should be taken to assure that positive drainage is maintained at all times in the transitions between the mainline edge and auxiliary lanes, ramp lanes and shoulders.
The grinding operation produces a slurry of ground concrete and water to cool the blades. The slurry is chemically inert and can be discharged onto the shoulder area or vacuumed into trucks depending on the location of the project. Prior to beginning the grinding operation, the Engineer will approve the disposal method. At no time should slurry be discharged within 100 feet of any natural stream or lake or within 5 feet of a water-filled ditch. Nor should it be allowed to enter a closed drain system. Check the project proposal for allowed discharge areas.
Random samples of the slurry should be taken for chemical testing of the grinding residue and cooling water.
The inspector should make the following checks during the diamond grinding operation:
- Overlap of successive passes of grinding head
- Blade Spalling
- Aggregate hardness
- Sand Patch test to verify macro texture depth
Dowel bar retrofit commonly referred to as DBR is a repair procedure typically used on concrete pavement that exhibits intermittent transverse cracking. This repair is typically used to restore load transfer at the location of the crack.
Dowel bar retrofits are not appropriate for all pavements that have transverse cracking. Good candidate concrete pavements that should be retrofit have little or no spalling at the surface of the crack to be repaired. The crack should also be level, not faulted, from one side to the other. Attempting to DBR a pavement that exhibits spalled or faulted joints will result in failure of the DBR. Contact the Pavement Structures Unit at C&T Division for questions regarding the appropriate use of DBR.
See various descriptions below for examples of pavements that are good candidates for a DBR.
- Slots shall be cut using a diamond-bladed saw machine.
- The machine shall typically be capable of cutting a minimum of three slots simultaneously that are centered over the crack.
- Slots shall also be centered over the crack or as directed by the Engineer.
- If the crack wanders, the slots shall be cut to have a specified minimum overlap of the dowel bar on each side of the crack according to the specification.
- The Contractor shall visibly mark the cracks along their length so that the slot cutter can see them to properly place the slots.
- The concrete remaining in the slots after sawing shall be removed with lightweight chipping hammers no greater than 30 lbs.
- The Contractor must provide manufacturer specifications to verify the capacity of the chipping hammers is no greater than 30 lbs.
- Concrete shall be removed in such a manner so as to prevent any pavement fractures caused by the removal operations.
- If the Contractor is allowed to use chipping hammers larger than 30 lbs, micro cracking of the remaining concrete will occur.
- Minor spalls, intermediate and major spalls shall be repaired using the patching material used to backfill the slot in accordance with Section 6 of the Standard Specifications for Construction.
- Any loose concrete shall be vacuumed or removed from the slot and all surfaces shall be dry, abrasive blast cleaned.
- Any exposed steel shall be blast cleaned to remove any rust or laitance.
- Immediately prior to placement of the dowels and patching material, the slots shall be final cleaned with moisture-free, oil-free compressed air having a minimum pressure of 90 psi.
- After final cleaning, the crack shall be sealed with a bond breaker tape or joint sealant to prevent the patching material from entering the crack.
- When aligned correctly, dowels shall be true to the pavement surface and parallel to the pavement centerline.
- Bond release agents shall be applied over the entire dowel bar prior to placing the dowel bar into the slots.
- Any bond release agent spilled on any slot surface shall be immediately removed and the slot surface cleaned.
- The patching material shall be mixed with a portable or mobile mixer.
- The patching material shall then be consolidated using a hand-held vibrator or as recommended by the manufacturer.
- The surface of the patch shall be finished flush with the surrounding concrete and cured according to manufacturer’s recommendations.
- The surface must be finished flush with the surrounding surface even if diamond-grinding of the concrete surface is to occur afterward.
- The slot walls and bottom must be dry before placement of the patching material, unless otherwise recommended by the manufacturer.
- The patching material can be tested as necessary to verify that the mixture meets the specification.
- The patching material shall be cured for the minimum time required by the contract specification before placing any vehicle loads on the repair.
Measuring Pavement Macro Texture Depth Procedure as follows:
- Select a dry homogeneous area that contains no unique features.
- Clean surface using a clean wire brush.
- Position a portable wind screen around the surface.
- Fill cylinder of known volume with dry silica sand. Sand will be furnished with the kit. (100% passing the #60 sieve, but 100% retained on the #80 sieve).
- Gently tap base of cylinder several times to fill voids and top off cylinder with more material.
- Pour measured volume of sand on cleaned surface protected from winds.
- Carefully spread material in a circular motion with hockey puck.
- Measure and record the diameter of the circular area covered by the sand at four equally spaced locations around the circumference. Compute and record the following:
Average of the four depth measurements (ave. D)
Mean texture depth, in = 4.1 (ave.D)2
Note: The constant is derived for use with a measuring container having a calibrated volume of 3.2 cubic inches.
Special provisions currently govern requirements for performance warranties on all Capital Preventive Maintenance projects. These special provisions will be in the project proposal. Copies of all forms referenced in this section can be found in the Capital Preventive Maintenance Program Manual.
Prior to award of the contract, the Contractor must supply the Department a warranty, performance and lien bond. The warranty bonds furnished by the Contractor are in an amount equal to 100% of the contract total. In addition to those bonds, the Contractor must also complete a warranty form. The bonds and warranty form are retained in the Contract Section’s files.
During construction, the Department is responsible for inspection of the job to assure the Contractor is using the specified materials and that their construction and traffic control methods are meeting the contract requirements. The Contractor’s Daily Report is a generic report that should be used on all Preventive Maintenance warranty projects to document required information. This report supplements the daily documentation required, per specification, for each specific treatment. The Contractor will complete the form on a daily basis in addition to all other documentation required by the specifications. The intent of the form is to aid the project office in tracking the project status and pay items.
After completion of construction of the warrantied work, the Department and the Contractor will review the work for compliance with the contract. If the work is determined by the Department to not be in compliance, the Contractor shall be required to repair the defects. When the work is in compliance, a form entitled “Initial Acceptance for Preventive Maintenance Warranty” form will be completed by the Department and the Contractor to document the acceptance date of construction.
The Initial acceptance form is used to document the starting date of the warranty period, upon departmental acceptance of the surface treatment. This form may be used for the entire project or for portions of a project. The Project Engineer and the Contractor will review the surface treatment to confirm that it meets the project specifications. Once both agree that the surface treatment is in compliance with the project specifications, the form is completed and signed by both parties. A copy is then sent to the Surety Company by the Contractor. A copy of the form should be retained in the project office’s project file and the original sent to Financial Services - Payments.
During the warranty period, the Department is responsible for monitoring the preventive maintenance surface treatment for compliance with the warranty performance criteria. The Project Engineer should use the Field Evaluation of Warranty Performance form to document the condition of the surface treatment during the warranty period as related to the warranty performance criteria.
If the surface treatment exceeds the threshold limits, as defined in the project warranty specification, the Department will notify the Contractor, in writing, of the required warranty work. The Department will provide the Contractor all written reports of the surface treatment’s condition relating to the warranty performance criteria.
If the Contractor disagrees with the findings of the Department, a Conflict Resolution Team (CRT) will be established. The CRT will consist of a five-member team. The Department and the Contractor will each select two representatives for the CRT. A third Party Member will be mutually selected by the Department and the Contractor to complete the CRT. See “Conflict Resolution Process” in the Capital Preventive Maintenance Program Manual for detailed information on this process.
Refer to the special provisions and the Guidelines for Administering Warranties on Road and Bridge Construction Contracts for more information on warranty rights and responsibilities.
If warranty work is required, the Contractor must supply a supplemental performance and lien bond to the Project Engineer for all warranty work identified that is consist with the warranty specification performance criteria. The supplemental performance and lien bonds should be retained in the project office’s project file. In addition to supplemental bonds, the Contractor is required to furnish new insurance documentation, to the Project Engineer, for the warranty work in accordance with subsection 107.10 of the Standard Specifications for Construction. The new insurance coverage shall be consistent with that of the original contract. All insurance documentation should be retained in the project office’s project file.