Concrete Pavement Preservation Partial Depth Repairs

Transcription

1 Concrete Pavement Preservation Partial Depth Repairs National Concrete Pavement Technology Center North Dakota Ready Mix and Concrete Products Association Dan Frentress P.E. IGGA 1

2 Partial-Depth Repair Purpose: Repair surface distresses Reestablish joint reservoir Used for: Midslab surface spalling Joint spalling Severe scaling Remove and Replace Deteriorated Surface Concrete

3 Benefits Restores structural integrity Improves ride quality Extends the service life Restores a well-defined uniform joint sealant reservoir 3

4 Good Candidate Projects Spalls caused by: Incompressibles in joints Localized areas of weak material Joint inserts Surface deterioration caused by: Reinforcing steel too close to surface Poor curing or finishing practices Recommended evaluation procedures: Distress surveys Sounding and cores from pavement 4

5 Poor Candidate Projects Spalls due to dowel bar misalignment Spalls at working cracks due to shrinkage, fatigue, or foundation movement Spalls due to D-cracking or reactive aggregate 5

6 Good Candidate? PDR Placed in 1992 Picture taken in

7 Bad Candidate! 7

8 Good Candidate? 8

9 Material Selection Factors Allowable lane closure time Ambient temperature Cost Size of repair Estimated performance Normal opening strength for partial depth repairs to 1,800 to 3,000 psi Most agencies maintain a Qualified Products List that provides approved materials for use by the agency. 9

10 Construction Steps 1. Repair dimension selection 2. Concrete removal 3. Repair area preparation 4. Joint preparation 5. Bonding agent application 6. Patch material placement 7. Curing 8. Diamond grinding (optional) 9. Joint sealing 10

11 Repair Dimension Selection Sounding 11

12 Repair Dimension Selection (TOP VIEW) Boundary saw cuts min. 2 in. (50 mm) deep, 3 in. (76 mm) outside distressed area. Overlap cuts at corners and approx. 1 in. (25 mm) across joint. Saw cut approx. 2 in. (51 mm) away from joint for protecting opposite face. Saw cut skimming opposite joint to provide clean vertical face. 12

13 Concrete Removal Saw-and-Remove Diamond-bladed saws are used. Sawing provides vertical faces and square corners. The initial sawcut may be either at those marked boundaries at 2: deep or at the boundaries and in a criss-cross pattern. Material is removed with lightweight jackhammers. PROS: Very little spalling of remaining pavement occurs. Crews are typically familiar with this method. CONS: Water from sawing leaves area saturated, possibly delaying the repair process. Polished vertical edges may lead to poor bonding. 13

14 Concrete Removal Jackhammering Removal begins at center and extends outward Remove top 1/3 but no more Care not to fracture sound concrete Removal near joints should be done w/10-15 lb. hammer to avoid damage Operate hammer no greater than 35% 14

15 Concrete Removal Cold Milling Transverse Milling (small head, moves along joint) Longitudinal Milling (wide head, pick up & move over) Some states (at least MO, MI, WI, and MN) have had good success using cold milling. PROS: Rough, irregular surface that promotes bonding. Efficient and economical when repairing large areas. CONS: May cause spalling on adjacent pavement edges. Equipment may be difficult or expensive to obtain for some projects. Small patches (<3 ft2) cannot be fixed using this method. Creates a standard size, which may not conform to site needs. 15

16 Minnesota Standard This standard developed and used by the Minnesota DOT allows the contractor to choose milling or jack hammers for removal of deteriorated concrete. Milling Option Requires a taper of two inches difference between the bottom of the patch and the top of the patch. 10 bottom vs. 12 top. Allows the use of a rounded edge left be the mill and the use of light jack hammers to remove any delaminated concrete exposed by the milling operation. Sand is allowed under exposed dowel bars on a limited basis. Sawing and Chipping Option Saw around the removal area to a depth of 2 inches. Use a light jack hammer of 35 lbs or less to remove the deteriorated concrete. A taper of between degrees is required between the bottom of the repair to the top. 10 bottom vs. 12 top. Sand is allowed under exposed dowel bars on a limited basis. Exposed dowels must be coated with duct tape to prevent bonding to patch mix. 16

17 Minnesota Standard Plate for PDR 17

18 Milling Machine-V Head for Partial Depth Patch Weight 9 Tons Little dust Removal rate 8 ft. / minute 18

19 Skid Steer for Milling Partial Depths Best suited for corner spalls and random cracks, it can maneuver better than the larger mills. Skid Steers weigh about 8000 pounds and can have removal rates of 2 3 feet per minute. Light weight skid steers can cause spalling at edges, but most minor spalls will be patched with concrete mix. It is easy to lift the front end off the ground during milling, but can be done with minor spalling. 19

20 Concrete Removal Cold Milling Milling Across the Joint Milling Along the Joint 20

21 Checking for Sound Concrete Done after the Mill Use lightweight jack hammer (15 30 lbs) for any debris removal 21

22 Joint Preparation joint 75 3 mm Remove bond breaker after patch finished & seal joint scoring 75 3 mm Plan View bond breaker Polystyrene Polyethylene patch pavement 25 1 mm 1 in = 25.4mm Profile View Fig. 5.3 on p

23 Partial-Depth Repair Need for Compressible Insert Point Bearing Popout & Breakage Joint Closure Debonding Expansion Expansion 23

24 Example of Compression Relief Failure of Partial Depth Joint Repair BELIEVE IT when it calls for Compression Relief 24

25 Repair Area Preparation Sandblasting 26

26 Repair Area Preparation Air Blowing Air blow to remove dust and debris Minimum 90 psi Free of oil and moisture Direct away from patches 27

27 Final Blowing of Debris with Leaf Blower 28

28 Milled Crack and Joint 29

29 Ankeny Partial Depth 30

30 Fill Void Below Joint Use Sand to provide compression relief in milled crack (no lockup) Must use caution when needing to do a lot of this before patching Repair will not last as long as one placed in sound concrete 31

31 Precautionary Note in Specs Sand can prevent locking of the joints together due to concrete infiltration when placing repairs. This will probably result in a reduced repair life. The following is an example of over using the sand principle. Duct tape is an excellent way to prevent bond on exposed old dowel bars. 32

32 Hole to Bottom 33

33 Minnesota Standard Plate 34

34 Bonding Agent Application Surface should be clean and in a saturated, surface-dry condition. Apply cementitious bonding agents with a wire brush; apply epoxy bonding agents with a soft brush. Coat all horizontal and vertical surfaces. Excess grout or epoxy should not be permitted to collect in pockets. Cement Grout The grout should be placed immediately before the repair material so that the grout does not set. Any bonding material that is allowed to set must be removed. Epoxy 35

35 2 Parts Type I Cement 1 Part Water 1 Part Sand Grout Recipe Mixed to the consistency of thick cream or kool whip Placement immediately before concrete. Has a shelf life of 60 minutes. 36

36 Grout used to Seal Edges of Partial Depth Repairs 37

37 Patch Material Placement Batch small quantities PCC materials should be placed when the temperature is above 4 C (40 F) and rising Some epoxy materials placed in lifts Overfill patch area by ~3 mm (1/8 in) Consolidate material with small spud vibrator Screed and hand trowel, working from the center of the patch to the edges 38

38 Mobile Concrete Batch Plant It has 5 bins that hold sand, aggregate and cement products to batch small quantities of material. It uses a belt scale to control the mix proportions for the patch mix being produced. 39

39 Hand Batching Methods Mixed by proportions on the back of a truck Buy prepackaged bags of material One such product is the Minnesota 3U18 mix 40

40 Sample Minnesota Partial Depth Mix 3U18 Partial Depth Mix Small Aggregate 100% passing 3/8 sieve Per Cubic Yard 850 lbs Type I Cement Uses 295 pounds of water Uses 1328 pounds of Coarse Aggregate Uses 1328 pounds of Sand A target W/C of 0.35 Type E Water Reducing and Accelerator 6.5% Air Maximum 1 inch slump Cure time of 12 hours Coarse Aggregate gradation will be the following 100% passing the 3/8 inch sieve 55% - 95% passing the #4 sieve Not more than 5% shall pass the #50 sieve 41

41 Patch Material Placement 42

42 Finishing Tip 43

43 Sealing Edges and Runouts The edges of the repair should be sealed with grout to help prevent moisture infiltration, as shown in the photo. 44

44 Curing P.D.P. Have large surface areas in relation to their volumes (which can lead to rapid moisture loss) Prevent moisture loss White-pigmented curing compound commonly used (some require 1.5 to 2 times normal rate) Opening to traffic Mix / temperature dependent Common values: 1,800 to 3,000 psi 45

45 Completed Partial Depth Repairs Transverse Joint done in 1987 Random Crack done in 1999 Picture taken in 1999 City Street in South St Paul, MN. 46

46 Rochester, Mn 2007 Patch Picture

47 CASH 22 East side of Rochester, Mn PDR in

48 Partial Depth Longitudinal Crack Repair 49

49 I-35 South of Duluth, Mn Project done in 1991 Picture taken in 2000 Centerline 8 miles long 50

50 Deteriorated Areas were not Repaired in Original Work (Joint and Crack had received a Partial Depth Repair on either side of Deteriorated Areas) 51

51 Key Factors For Success Proper selection of candidate projects Proper material selection Identification of repair boundaries Use of joint/crack reformers Achieving good bond Patch area clean and dry Sandblasting sidewalls Application of bonding agent Proper placement and curing 52

52 PDR and DBR Hwy 71 North of Windom, MN Built in 1962 with Quartzite Rock Partial Depth and Dowel Bar Retrofit, Diamond Grinding in

53 Mn/Road DBR in Existing Basket 54

54 Mn/Road Test Facility 55

55 Mn/Road Old WB I-94 First time the old concrete pavement is being used for research. Built in concrete thickness 24 wide 27 Reinforced panels with Skewed Joints 56

56 Faulted Slabs 57

57 Locate Old Dowels with MIT Scan 58

58 Old Dowels Marked in Red 59

59 Slot Removal Max 30 lb. Chipping Jack Hammers 60

60 Slot Removal Some existing dowel basket shipping wires found in rubble. Old dowels were 1 X 18 No epoxy coating 61

61 View of hole at side of Slot 62

62 Sheet Rock Compound House construction Sheet Rock compound used to fill hole next to slots. With Excessive compound use Performance is questionable!!! 63

63 Broken Dowel 64

64 Some Holes at bottom of Slot 65

65 Dowel Placement 66

66 Concrete Placement 67

67 Inside Wheel Paths 100 IWP - All Points (Before and After Joint) & Load Levels Fall IWP Spring IWP

68 Mn/Road DBR in Existing Basket 69

69 Questions? International Grooving and Grinding Association Website Daniel P. Frentress P.E. Office Phone Cell