Full Depth Repairs By Arahim

Full Depth Repairs for Rigid Pavements Presented To: Dr. Sajjad Maqbool Presented By: Abdur Rahim Rajar 06-MS-TE-10

Presentation Organization  Introduction  CPR Techniques  Selection of Candidate Projects for FDR  Design Considerations  Material Considerations  Construction Procedure  Full-Depth Repair of PCC Pavement Checklist  Performance  Cost  References 2

Introduction  Full-depth repair (FDR) is a concrete pavement restoration (CPR) technique that can be used to restore the structural integrity and rideability to concrete pavements having certain types of distresses.  It involves making lane-width, full-depth saw cuts to remove the deteriorated concrete down to the base, repairing the disturbed base, installing load-transfer devices, and refilling the excavated area with new concrete. 3

Introduction  When normal maintenance procedures can no longer correct the effects of ordinary pavement wear or use, fulldepth repair may become necessary to restore damaged.  It is an effective, permanent treatment to repair pavement distresses particularly those that occur at or near joints and cracks. 4

FULL DEPTH REPAIR

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CPR techniques

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Selection of Candidate Projects  The need for full-depth repairs should be determined based on  the type  frequency, and  severity of existing deterioration of the pavement.

 Recommendations are provided in Table as to the level of severity of each distress type that warrants full-depth repairs.  Agency should examine these recommendations and modify them as needed to more closely fit local conditions 7

General distress criteria for full-depth repair DISTRESS TYPE

MINIMUM SEVERITY LEVEL REQUIRED FOR FULL-DEPTH REPAIR

Jointed Plain & Jointed Reinforced Concrete (JPC & JRC) Pavement Blowup

Low

Corner Break

Low

D-Cracking

Medium

Deterioration Adjacent to Existing Repair

Medium

Joint Deterioration

Medium (with faulting 6mm (0.25in))

Spalling

Medium

Reactive Aggregate

Medium

Transverse Cracking

Medium (with faulting 6mm (0.25in))

Longitudinal Cracking

High (with faulting 12mm (0.5in)) 8

General distress criteria for full-depth repair DISTRESS TYPE

MINIMUM SEVERITY LEVEL REQUIRED FOR FULL-DEPTH REPAIR

Continuously Reinforced Concrete (CRC) Pavement Blowup

Low

Punchout

Medium (with faulting 6mm (0.25in))

Transverse Cracking (Steel Rupture)

Medium (with faulting 6mm (0.25in))

Localized Distress

Medium

Construction Joint Distress

Medium

D-cracking

High

Longitudinal Cracking

High (with faulting 12 mm (0.5in))

Repair Deterioration

High 9

Pavement Distresses that Require Full-Depth Patching  Transverse Cracking

Medium Severity Transverse (Mid-panel) Crack 10

Pavement Distresses that Require Full-Depth Patching  Transverse Cracking

 Pavements with transverse cracks of medium and high severity are recommended for full-depth repairs.  Some cracks that extend through the depth of a slab can begin moving and functioning as joints (working cracks).  Working cracks develop and deteriorate from one or more of these causes:       

Lock-up of the dowel bars in a near by joint Rupture or corrosion of steel in jointed-reinforced slab Poor joint spacing Loss of aggregate interlock along the crack face Inadequate joint sawing Excessive curling and warping of slabs Lack of subgrade support

 Hairline cracks do not extend to the bottom of a slab do not require any special treatment, (e.g., plastic shrinkage cracks).

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Pavement Distresses that Require Full-Depth Patching  Longitudinal Cracking  When longitudinal cracks deteriorate to a high severity condition, they warrant full-depth repairs.  A high severity condition indicates that a crack is greater than 12 mm (0.5 in) wide, spalling extends more than 150 mm (6 in) from the crack, and faulting is greater than 12 mm (0.5 in).  If the condition is less severe, other CPR procedures, such as partial depth repairs, retrofit dowel bars, or sawing and sealing are sufficient.

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Pavement Distresses that Require Full-Depth Patching  "D" cracking

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Pavement Distresses that Require Full-Depth Patching  "D" cracking

 D" cracking is a pattern of cracks caused by the freeze-thaw expansive pressures of certain coarse aggregates.  The disintegration and spalling associated with these stresses normally begins near the joints as a result of the higher moisture levels necessary for the course aggregates to expand in volume during freezing.  Medium and high severity "D" cracking could warrant full depth repair.  However, like for any other materials related distress, FDR only provides a temporary treatment.

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Pavement Distresses that Require Full-Depth Patching  Shattered Slabs & Corner Breaks

 Corner breaks and intersecting cracks develop in slabs receiving marginal support from the subbase or subgrade.  Over time the unsupported slab will pump subbase or subgrade fines out from beneath the slab, leading to voids and eventual cracking over the uneven support.  Shattered slabs also may result from frost heave or swelling soil problems.  Shattered slabs and corner breaks are good candidates for using FDR.

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Pavement Distresses that Require Full-Depth Patching  Punchouts

Punchout of CRC Pavement

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Pavement Distresses that Require Full-Depth Patching  Punchouts  Punchouts in continuously reinforced concrete pavements (CRCP) are candidates for full-depth repairs as they represent a structural failure of the pavement.  They form after many load cycles when the longitudinal steel ruptures along the faces of two closely spaced cracks, usually less than 0.6 m (2 ft) apart. 17

Pavement Distresses that Require Full-Depth Patching  Blowups  Occur in hot weather at transverse joints or cracks which do not allow sufficient expansion of the concrete slabs.  The insufficient expansion width of joints is usually caused by infiltration of incompressible material into the joint.  Blowups of any severity warrant full-depth repairs due to the localized disruption to pavement integrity and the potential safety hazard. 18

Design Considerations  Full-depth repairs that are properly designed and constructed will provide good long-term performance for as long as the surrounding concrete pavement.  The overall condition of the pavement and the extent of deterioration should be carefully examined to ensure that the placement of full-depth repairs will perform as intended. 19

Factors requiring careful consideration for successful implementation of FDR  Joint design, including load transfer.  Selection of repair locations and boundaries  Material selection  Preparation of repair area  Concrete placement and finishing  Joint sealing  Curing and opening to traffic 20

Rule of Thumb  If deterioration is 25 percent or less of the total concrete pavement thickness, apply a surface patch.

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Rule of Thumb  If deterioration is more than 25 percent of the total concrete pavement thickness, apply a full-depth repair.

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Design Considerations  The following are important design considerations: 1.Pavement type (jointed or continuously reinforced) 2.Patch size (for distress and subgrade conditions) 3.Load transfer (dowels versus other methods). 4.Causes of failure 23

1. Pavement type (JCP &CRCP)  Jointed concrete pavements (JCP)  

Jointed concrete pavements typically require far more repairs at joints than between joints. Some pavements may have joints with very little deterioration but one or more mid-panel cracks in each slab opened wide and essentially acting as joints.

 Continuously Reinforced Concrete Pavements (CRCP)  

Most full-depth repairs on CRCP will be placed at the areas exhibiting punchouts and other localized distresses Full-depth repairs may also be required at medium and high severity transverse cracks in which the steel has ruptured. 24

2. Patch Size  It is important that the boundaries be located so that all significant distresses are removed.  Deterioration near joints and cracks may be greater at the bottom of the slab than at the top of the slab. Therefore, further investigation should be performed.  A minimum patch length of 1.8m (6 ft) and full-lane patch width of 3.6m (12 ft) is recommended to provide stability and to prevent longitudinal cracking. For the same reason, the minimum remainder of the slab must be at least 1.8m (6 ft).  Combining two smaller patches into one large25

2. Patch Size

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3. Load Transfer  Jointed Pavements  The design of the retrofit dowel layouts includes the number of devices, diameter, and spacing of the dowel bars.

Recommend dowel bar design for interstate-type pavements

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3. Load Transfer  Continuously Reinforced Pavements  For full-depth patching in continuously reinforced pavements, new steel bars are necessary to maintain the continuity of the reinforcing bars that run longitudinally through the pavement.  Reliable methods to attach the new bars to the salvaged lengths of the old bars include tied splices, mechanical fastened splices and welded splices. 28

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3. Load Transfer  Continuously Reinforced Pavements

Steel splice techniques for CRCP

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Material Considerations  The concrete mixture design should be based on the available lane closure time.  Typical full-depth repairs operations utilize concrete mixes containing 390-502kg/m3 (658-846 lbs/yd3) of either cement Type I or Type III cement.  A set-accelerator is frequently used to permit opening in 4 to 6 hours.  Using insulating blankets ( or boards) during the first few hours after placement also can improve the strength development of any mix.

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Material Considerations  Concrete mixture for full-depth repairs should have the following properties:  6.5 ± 1.5 percent of entrained air in the concrete (less air may be permissible in nonfreeze areas).  50 to 100 mm (2 to 4 in.) slump

 Non chloride accelerators are recommended for CRCP and JRCP fulldepth repairs. 31

Construction Procedure 1. Define repair boundaries area 2. Saw old concrete 3. Remove old concrete 4. Prepare patch area 5. Provide load transfer 6. Place and finish concrete 7. Cure and insulate concrete 8. Saw and seal joints 32

1. Define repair boundaries area  Repair boundaries can be determined by making a field survey utilizing data from initial project survey.  Each distressed area should be examined and the repair boundaries marked on the slab surface.  If the project plans contain partial-depth repairs, the project specifications should include a special provision that provides the engineer freedom to change some partialdepth repair to full-depth repairs. 33

1. Define repair boundaries area Guidelines for locating repair boundaries are provided below:  The recommended minimum repair length is  1.8m (6 ft) for repairs provided with mechanical loadtransfer devices,  All repairs should be full-lane width.  The minimum recommended distance from the full-depth repair joints to the nearest transverse crack or joint is 1.8m (6 ft).  A boundary that would fall at an existing doweled transverse joint should be extended 0.3 m (1 ft) to include the existing joint.  Reinforcement is needed in JRCP where the patch length is longer than 4.6m (15 ft). It may be more economical to place additional doweled transverse joints at 4.6m 34 interval than to place reinforcement.

Saw Old Concrete

Full-depth Sawing transverse boundaries

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2. Saw Old Concrete  Before removing deteriorated concrete, isolate the area from adjacent concrete and shoulder materials using full-depth saw cuts.  It is preferable to use diamond-bladed saws for full-depth transverse cuts.  To avoid spalling damage during removal, the sawing operation should be continued through the joint. 36

3. Remove Old Concrete  Sawing operations should not precede removal and repair operations by more than two days.  There are two basic methods of removing deteriorated concrete from the repair area:  Liftout  Breakup 37

3. Remove Old Concrete

Liftout operation chain for removing existing slab 38

3. Remove Old Concrete

Drop Hammer breaks the deteriorated concrete

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4. Prepare the Patch Area

Vibratory Plate Compactors

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4. Prepare the Patch Area  After removing the old concrete and loose material, the area is ready for subbase preparation  If removing operations damage the subbase, it may be necessary to add and compact new subbase material.  Ideal backfill materials can reach optimum compaction with small plate compactors that can maneuver in the confined patch area.

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5. Provide Load Transfer  Hole diameter  Cleaning Holes  Installing Dowels  Prepare Longitudinal Joints  Full slab replacements and repairs longer than 4.5 m (15 ft) require a tie system

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5. Provide Load Transfer

Injecting grout or epoxy and inserting dowels 43

5. Provide Load Transfer

Grout-retention Disk

Installation of Bond-breaking Board

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6. Place and Finish the New Concrete  Placing Concrete  Finishing & Texturing

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7. Curing  Apply the curing compound and insulation as soon as possible after finishing the surface.  A liquid-membrane-forming curing compound is adequate  To prevent moisture loss and to protect the surface, place one layer of polyethylene sheeting on the patch surface under the insulating boards or mats.  Avoid using insulating boards during very warm temperatures, this may caused concrete to undergo thermal shock when they are removed.  Smoothness - A good finishing technique can develop an adequate transition between the patch and old concrete.  In some cases, a ride specification comparable to the local ride specification may be needed for CPR projects. Patched pavements that do not meet a specified ride requirement will require correction by diamond grinding. 46

8. Saw and Seal joint  The final step is to form or saw transverse and longitudinal joint sealant reservoirs at the patch boundaries.  Sealed perimeter joints will lower the potential for spalling at the patch joints.  Hot-poured asphalt-rubber sealants are most commonly specified for longitudinal joints and higher type sealants to such as low modulus silicone are commonly used for transverse joints. 47

9. Opening to Traffic  There are two methods to determine when to open full-depth repairs to traffic:  Specified minimum strength  Specified minimum time after completing placement

 For most concrete pavement applications, it is preferable to measure the concrete strength to determine when it is acceptable for traffic. 48

9. Opening to Traffic  Recommended minimum strength for traffic opening are :  Compressive Strength: 13.8 MPa (2,000 lbf/in2).  Modulus of Rupture: 2.1 Mpa (300 lbf/in2) center-point loading, or 1.7 Mpa (250 lbf/in2) third-point loading.

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9. Opening to Traffic

Typical "Opening to Traffic" time requirements for different Portland cement concrete mixes. For Mixes Using:

Typical Time to Opening Strength

Certain blended cements

2 - 4 hours

Sulfo-aluminate cements

2 - 4 hours

Type III cement with non-chloride accelerating admixture

4 - 6 hours

Type III cement with calcium chloride (CaCl2) accelerator

4 - 6 hours

Type I cement with calcium chloride (CaCl2) accelerator

6 - 8 hours

Type III cement with Type A water-reducing admixture

12 - 24 hours

Type I (air-entrained paving mix without fly ash)

24 - 72 hours

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Full-Depth Repair of Portland Cement Concrete Pavement Checklist

Performance  Full-depth repairs can be designed and constructed to provide good long-term performance (10 or more years), while the performance of full-depth repairs on many in service pavements has been inconsistent.  Causes of premature failures of full-depth repairs include inadequate design (particularly poor load transfer design), and poor construction quality In addition, the effectiveness of some full-depth repair installations has been limited due to their placement on pavements that are too far deteriorated.  If properly designed and constructed, full-depth repairs can provide near-permanent rehabilitation of the distressed areas. 52

Performance  Important points for consideration in selecting this repair technique include the following:  If the existing pavement is structurally deficient, or is nearing end of its fatigue life, a structural enhancement (such as an overlay) is needed to prevent continued cracking of the original pavement.  If the deteriorations is widespread over the entire project length, an overlay or reconstruction may be more cost effective.  If the original pavement has a severe material problem (Materials related distress), full-depth repairs may only provide temporary relief from roughness caused by spalling.  Additional joints introduced by full-depth repairs add to the pavement roughness, even if the pavement is diamond ground after the repairs are made. 53  Nondeteriorated cracks in JPCP may be repaired by

Performance  The effectiveness of full-depth repairs depends strongly on  Installation of the repairs at the appropriate time in the life of the pavement  On the proper design and installation of the load transfer system.

 The overall condition of the pavement and the extent of deterioration should be carefully examined to ensure that full-depth repairs will perform as intended.

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Cost  The cost for full-depth repairs on jointed concrete pavements varies significantly, depending on the locality and site conditions (e.g., traffic).  Typical costs for 1.8 m (6 ft) repairs on a 250mm(10 in) slab range from $60/m2 to $120/m2  Repair costs for CRCP are significantly higher.  Since the highest cost items for full-depth repairs are full-depth sawing and joints (including load transfer), the unit costs of repair can be reduced significantly when a larger area is involved.  The replacement of the entire slab is a more costeffective solution than the placement of a series of smaller repairs within the same slab, and it is also more reliable. 55

CONCLUSIONS  The overall condition of the pavement and the extent of deterioration should be carefully examined to ensure that full-depth repairs will perform as intended.  An agency may stipulate that the repair attain a minimum strength before it may be open to traffic.  Agency should examine recommendations made by FHWA and modify them as needed to more closely fit local conditions.  The replacement of the entire slab is a more costeffective solution than the placement of a series of smaller repairs within the same slab, and it is also more reliable.  Appropriate usage is very important to obtain 56 desired performance.

CONCLUSIONS  The effectiveness of full-depth repairs depends strongly on the installation of the repairs at the appropriate time in the life of the pavement and on the proper design and installation of the load transfer system.  The overall condition of the pavement and the extent of deterioration should be carefully examined to ensure that full-depth repairs will perform as intended.  Patched pavements that do not meet a specified ride requirement will require correction by diamond grinding.  If the distressed areas in both lanes are similar and both lanes are to be repaired, aligning repair boundaries to avoid small offsets and to maintain 57 continuity may be desirable

References:  Federal Highway Administration (FHWA), 1998. Techniques for Pavement Rehabilitation, Publication No. FHWA HI-98033.  American Concrete Pavement Association (ACPA), 1995. Guidelines for Full-Depth Repair. TB002.02P. American Concrete Pavement Association, Skokie, IL.

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