Asphalt Paving Inspection Reminders and Changes to the Asphalt Field Density Program Regional Asphalt Meetings

1. Asphalt Paving Inspection Reminders and Changes to the Asphalt Field Density ProgramRegional Asphalt Meetings March 2010

2. 2 Topics/Field Issue Areas� Keys to Asphalt Paving Inspection Pre-AC Overlay/Inlay Laydown Compaction Changes to the Asphalt Field Density Program For asphalt concrete, I plan on covering four main areas in this recertification:For asphalt concrete, I plan on covering four main areas in this recertification:

3. 3 Pothole Patching Why an issue � potholes form where weak materials exist, either bound or unbound. If not patched prior to paving, density will not be achieved, the pavement will sink and the pothole will reform

4. 4 Non-Typical Pothole This happened in 2007 Laborer lost his shovel and did not tell anyone Shovel was rolled and inspectors happened to notice hump in matThis happened in 2007 Laborer lost his shovel and did not tell anyone Shovel was rolled and inspectors happened to notice hump in mat

5. 5 Proper Patching Technique � Permanent Patch Mark area of pavement to be removed � square or rectangle area Saw cut and remove bound material Re-compact base material Apply tack to vertical faces Place new AC material in appropriate lift thickness This is the best practice for patching a pothole. Where possible, use a roller or tamper. The last bullet is very important. If the pothole is six inches deep, do not try to fill it all at once. At least make two lifts.This is the best practice for patching a pothole. Where possible, use a roller or tamper. The last bullet is very important. If the pothole is six inches deep, do not try to fill it all at once. At least make two lifts.

6. 6 Milling Why an issue � can affect the placement and performance of pavement Scabbing Loose Material How many people think milling is an issue? Does it affect the overlay? Why do we mill? Remove a deteriorated layer or layers Maintain a grade Remove ruttingHow many people think milling is an issue? Does it affect the overlay? Why do we mill? Remove a deteriorated layer or layers Maintain a grade Remove rutting

7. 7 Scabbing What is it � unevenness of a milled surface What causes it � milling too fast, milling teeth in poor condition, improper milling depth What happens � uneven application of AC overlay Milling too fast causes the milling teeth to pull up chunks and not cut the asphalt. Same with dull milling teeth. If the aggregates are hard, then the milling teeth must be hard to get a good cut. Sometimes the milling depth specified results in scabbing. This must be addressed in the field by altering the milling depth to remove the scabbing. Finally, a poor bond between layers results in scabbing. This can be remedied by altering the milling depth.Milling too fast causes the milling teeth to pull up chunks and not cut the asphalt. Same with dull milling teeth. If the aggregates are hard, then the milling teeth must be hard to get a good cut. Sometimes the milling depth specified results in scabbing. This must be addressed in the field by altering the milling depth to remove the scabbing. Finally, a poor bond between layers results in scabbing. This can be remedied by altering the milling depth.

8. 8 How to Address Scabbing If milling teeth and speed acceptable, then change milling depth If specified for 1.5�, increase or reduce � depends on situation May be localized problem, change depth only in that area If scabbing is extensive, must evaluate impact on HMA tonnage Overrun on specified limits Reduce length of project to balance cost

9. 9 Tack Coat Application Why an issue � tack coat bonds the AC overlay to the existing surface On the mainline, lack of tack results in slippage/delamination At the joints, lack of tack results in poor compaction and density Tack is required between ALL LIFTS on new construction, milled surfaces and unmilled surfaces Tack is crucial to the performance of the pavement. Pavement gets its strength from thickness and strong materials. To achieve thickness, all of the bound layers must be �glued� together Tack is the glue. A new surface on a thick pavement will not last if tack has not been applied. The surface will crack.Tack is crucial to the performance of the pavement. Pavement gets its strength from thickness and strong materials. To achieve thickness, all of the bound layers must be �glued� together Tack is the glue. A new surface on a thick pavement will not last if tack has not been applied. The surface will crack.

10. 10 Why Do We Hate Tack? This was tack taken away from an overlay project in 2007 The plant is to the left. Trucks coming down the ramp left the tack; it was about 3/8� deepThis was tack taken away from an overlay project in 2007 The plant is to the left. Trucks coming down the ramp left the tack; it was about 3/8� deep

11. 11 Ways to Combat Tracking Let the tack break; break time a function of temperature and water content Use trackless tacking material (requirement in 2011) Use a spray bar paver

12. 12 Why Tack Coats Are Important � Bond! Here is a picture of what happens when we remove a core from the pavement. The effective pavement thickness is 4.5�. Cracks will form at the delaminated surface and lead to premature pavement failure.Here is a picture of what happens when we remove a core from the pavement. The effective pavement thickness is 4.5�. Cracks will form at the delaminated surface and lead to premature pavement failure.

13. 13 Which Do You Prefer? Here again, we only had a few nozzles working.Here again, we only had a few nozzles working.

14. 14 Which Meets Specification? None of the plates meet the specifications. The top plate meets the application rate, but was not uniform. The bottom left plate was too heavy. The bottom right plate was too light.None of the plates meet the specifications. The top plate meets the application rate, but was not uniform. The bottom left plate was too heavy. The bottom right plate was too light.

15. 15 Proper Longitudinal Joint Tacking The last picture was on a new construction project, here is a picture from a resurfacing project. Notice the tack applied to the joint. If you could look closer, you would see a puddle of tack. This is GOOD. One thing to remember, if you do not see overspray then you have to question if the tack was even applied.The last picture was on a new construction project, here is a picture from a resurfacing project. Notice the tack applied to the joint. If you could look closer, you would see a puddle of tack. This is GOOD. One thing to remember, if you do not see overspray then you have to question if the tack was even applied.

16. 16 Clean Paving Surfaces Why an issue � clean surfaces promote the bond between the new overlay and the existing pavement Dirty surfaces and debris lead to slippage and delamination Try placing a piece of tape on a dirty surface, the dirt sticks to the adhesive and the tape falls off. The same happens with an overlay.Try placing a piece of tape on a dirty surface, the dirt sticks to the adhesive and the tape falls off. The same happens with an overlay.

17. 17 Laydown Issues: Temperature (Air and Material) Transverse Joint Construction Longitudinal Joint Construction Paving Train We have discussed what to do prior to placing the AC, now we will focus on what to look for and do during the placement of the material.We have discussed what to do prior to placing the AC, now we will focus on what to look for and do during the placement of the material.

18. 18 The Road Base Temperature When to use the nomograph (how is latter in class)When to use the nomograph (how is latter in class)

19. 19 Temperature Limitations � Hot Mix Asphalt Surface Mixes Review chartReview chart

20. 20 Temperature Limitations � Stone Matrix Asphalt Review chartReview chart

21. 21 How Hot is TOO Hot? For PG 64-22 and PG 70-22, 350oF is maximum temperature at the plant For polymer modified mixes (PG 70-28 and PG 76-22), the maximum temperature is set by the binder supplier

22. 22 Temperature Limitations � Warm Mix Asphalt Minimum Base mix temperature � 40 oF Minimum Lay down Temperature � Not specified Review chartReview chart

23. 23 Transverse Joint Construction & Tie-In Why is transverse joint construction important? Smooth transition between old and new pavement Smooth transition from one day to the next IMPACTS RIDE QUALITY Check with a straight edge

24. 24 Transverse Joints What to do to make it smooth: Taper mill 25� � 50� from termini Use a finer mix for first and last load Roll the joint Measure with a straight edge Tack the joint face Remove temporary or loose material Start with a vertical face

25. 25 Longitudinal Joint Construction Why is longitudinal joint construction important? Achilles Heel for most pavements, main entry point for water Deterioration of joint leads to early pavement maintenance Many different approaches to construct the joint, no VDOT specification on density

26. 26 Early Signs of Joint Deterioration The picture on the left is of a pavement two years old The picture on the right is of a pavement placed in July 2004The picture on the left is of a pavement two years old The picture on the right is of a pavement placed in July 2004

27. 27 How Do You Make a Good Joint? Several Approaches A Few Keys to Success: Start with a straight joint Bump Back, but do not spread material with lute Have enough material to compact Tack the joint Roll the joint like the mainline, especially the centerline joint

28. 28 Luting Here the lute man is thinning out the AC This reduces the amount of material at the joint Extra material is needed along the joint to compact A smooth joint after rolling is not necessary a good joint. Side of joint just placed should be slightly higher than other sideHere the lute man is thinning out the AC This reduces the amount of material at the joint Extra material is needed along the joint to compact A smooth joint after rolling is not necessary a good joint. Side of joint just placed should be slightly higher than other side

29. 29 Paving Train Issues to consider: Keep the train moving, starting and stopping leads to bumps Slow and consistent speed helps with smoothness and density Use augers when screed extended helps with density and reduces segregation Keep the screed vibrating or tamping in order to get initial density

30. 30 Compaction Issues: Straight-Edge Roller Patterns and Joint Compaction Once the AC has been laid by the paver, now we need to make sure we get density.Once the AC has been laid by the paver, now we need to make sure we get density.

31. 31 Straight-Edge Straight Edge can be used for: Checking transverse joints Longitudinal joints to make sure you have a crown or cross slope Making the paver is laying an even matStraight Edge can be used for: Checking transverse joints Longitudinal joints to make sure you have a crown or cross slope Making the paver is laying an even mat

32. 32 Rolling the Mat Except for the weight of the paver screed, the remaining density is achieved through rollers Make sure the roller pattern is followed Make sure the edges and centerline joints are rolled Make sure there is material at cold joint for compaction

33. 33 Joint Construction Four types of joints: Transverse Internal Longitudinal Joint without cold joint (unconfined) Internal Longitudinal Joint with cold joint (confined) External Longitudinal joint with free edge (unconfined)

34. 34 Preferred Rolling Approach

35. 35 Unconfined Longitudinal Joints May be more difficult to compact, no edge restraint Avoid tender mixes Interior joint very important to pavement life

36. 36

37. 37 Density We are not constructing porous pavements Density needed to achieve desired pavement life

38. 38 Why Such A Fuss About Density??? VDOT Uses Contractor Test Results for AC Acceptance Code of Federal Regulations requires DOT�s have Quality Assurance Program VDOT uses density to accept HMA in the field. Since we use federal money, we must ensure density is met.VDOT uses density to accept HMA in the field. Since we use federal money, we must ensure density is met.

39. 39 To Comply with 23 CFR 637B Policy DOT must: Maintain qualified staff & testing Independent Assurance Program Verification Samples & Tests � QA Tests Random Samples � plant and field testing Contractor must: Maintain qualified staff and testing Independent checks of Equipment, Procedures and personnel Verification of test results Random Samples � plant and field testing How VDOT complies with federal law.How VDOT complies with federal law.

40. 40 VTM-76 Stratified Random Locations Control Strip Test Sections Cores for Control Strips 6 cores for new mixes 2 cores for subsequent control strips Cores are MANDATORY

41. 41 Roller Pattern Purpose � Determine maximum passes and coverage to attain density When: Beginning of a new course Change in Job Mix - Gradation or Source Change in Subsurface At direction of Materials Engineer Remember � If Change in equipment, new roller pattern not required

42. 42 Control Strip Verifies the Nuclear Density and determines the Target Density that is used to control acceptance for the rest of the project Reminders Use the same Number of Passes as determined in the Roller Pattern Select 10 Stratified Random Locations and Mark them with a Template and Paint Test each location and Average the Readings Cut Cores at the 3 sites Closest to the Average for Density Verification Your Target Density is the average of the ten (10) Nuclear Readings One-Minute Mode for the Nuclear Gauge

43. 43 Coring Supplies � Required in VTM 76

44. 44 Important Reminders for Control Strips Federal Aid NHS Projects the inspector must: Observe the extraction of cores/plugs (VTM-76) Observe the determination of % density (VTM-6 & VTM-22) Secure and maintain possession of cores/plugs for Material Section (contact materials section the same day cores were bulked to make arrangements for cores to be picked up) Requirement applies to: Federal Aid Plant Mix Schedule Projects on NHS Federal Aid Construction Projects on NHS

45. 45 Test Section(s) 5000 feet long, of any pass, regardless of width or thickness Divide into five 1000 foot Sublots Test 2 Labeled and Marked Stratified Random Locations in each sublot Compare test results with Target Density determined in Control Strip

46. 46 Test Section Longitudinal Joints Tested When QC test performed Test 4� from Joint on SM and IM; 6� for BM Results recorded on TL-59A Results not used for payment, but monitoring Action taken when measured density less than 95% of target

47. 47 Result of Longitudinal Joint Analysis

48. 48 Results of Longitudinal Joint Analysis

49. 49 Results of Longitudinal Joint Analysis

50. 50 Asphalt Field Density QA Program What it was What it will be

51. 51 Old Quality Assurance Program Project based VDOT monitoring with nuclear gauge or coring Each sublot monitored 20% of paving lane distance tested Control strips tested Independent assurance monitoring of technicians

52. 52 New Quality Assurance Program Two Functions: Verification sampling and testing (VST) Independent assurance (IA) Applications: Federal-Aid NHS Construction funded projects Federal-Aid NHS Maintenance funded projects

53. 53 IA Program Two Parts: Part 1: VDOT observation of contractor density technician Ensures technician can perform the duties per specification Completion of TL-141A Part 2: Reweighing cores from control strip Meet tolerance of 0.01 for Gsb Checks contractor technician and equipment; VDOT technician and equipment Completion of TL-141B One core per control strip; 10% of project control strips

54. 54 VST Program Core based program; cores obtained by contractor and given to VDOT Approximately 20% of lane paving mileage monitored 5,000 foot VST lots; one VST lot per 25,000 lane ft Two cores per lot Cores weighed in VDOT lab and compared to target from control strip cores (98% - 102%) Determine if material is passing or failing TL-140 used to record VDOT results Referee process includes additional cores

55. 55 Important Things to Know About VDOT�s QA Program Contractor must provide QC on all paving � mainline, trench widening, patching, etc. Type of QC based on project VDOT must perform VST and IA on all Federally Funded Projects on NHS VDOT should perform VDOT and IA on all other paving projects For construction projects, VST and IA quantities based on all paving on project � base lifts, intermediate, and surface mixes For maintenance projects, VST and IA quantities based on all paving mileage on a schedule/project

56. Asphalt Paving Inspection Reminders and Changes to the Asphalt Field Density ProgramRegional Asphalt Meetings March 2010