PAVEMENT MAINTENANCE II

1. Idaho Roads Scholar Program PAVEMENT MAINTENANCE II Part 1b: Chip Seal Construction

2. Objectives • Review how to set up a good chip seal, • Investigate equipment operation, and field checks, • Identify common problems and possible solutions.

3. Field Checks • Weather/Surface Condition • Traffic Control • Aggregate • Asphalt • Asphalt and Chip Distributor • Rollers • Sweeping

4. Weather/Surface Condition • Dry or Damp Surface • Temperature • Rain/Humidity • Wind

5. Surface Temperature

6. Proper Traffic Control is Essential!

7. Aggregate Requirements for Successful Seal Coat • Must be clean. • Less then 1% passing #200 sieve. • Cubical chips are better then flat chips. • Must be crushed. • At least 2 crushed faces. • More single sized the better.

8. Dirty Chips • > 1% passing the #200 sieve • Impedes the ability of binder to bond chip to roadway. • Limits amount of binder that can be applied. • Creates dust after sweeping.

9. Aggregate Condition • Emulsions => Damp Surface • Asphalt Cement => Dry Surface

10. Chip Considerations • Can only glue down a single layer of chips. • Must have chips at least 60 to 70% embedded to withstand traffic and snow plow damage. • Should see emulsion at top of chips before emulsion breaks.

11. Which are the better chips?

12. Distributors

13. Asphalt Distributor Components • Nozzles • Spray Bar Height • Application Rate • Product Temperature

14. Nozzle Angle

16. Spray Bar Height

18. Triple Coverage

19. Test Shot • Apply Asphalt Product for Known Distance & Width • Calculate Amount of Applied Asphalt Product • Calculate Spread Rate

20. Product Temperature • Typically 140 to 185oF • Check At Distributor

21. Common Emulsion: CRS-2P • Develops strength in hours that normally take days. • Sweep same day. • Requires clean chips. • Must place chips within one minute of placement of binder. • Eliminates bleeding • Higher softening point

22. Sample Asphalt Product • Sample Location • Truck or Trailer • Nozzle • Sample Container • 1 Gallon Plastic w/Lined Screw Cap, Wide Mouth

23. Chip Spreaders

24. Chip Spreader Issues • Correct Application Rate • Uniform Application Rate

25. Test Shot to Insure Correct Application Rate • Apply aggregate for known distance and width • Calculate Amount of Aggregate • Calculate Spread Rate

30. Check Rollers • Type • Weight • Speed

31. Rolling

33. Best Pneumatic-Tire Roller

34. Buns Up: Check Embedment

35. Factors Affecting Breaking and Curing • Weather Conditions: • temperature, humidity, wind • Water Absorption • Aggregate moisture content: • although wet aggregate may facilitate coating, it tends to slow the curing process • Mechanical forces: • roller pressure forces water from mix • Surface area: • excessive fines or dirty aggregate accelerate breaking • Surface chemistry

36. Broom

38. Safety • Approved Vests • Communication • Eye Contact

39. Typical Problems • Streaked Appearance • Bleeding/Flushing • Loss of Cover Aggregate • Bad Centerline Joint • Utilities/New Patches • Tight Alignment or Steep Grades • Heavy Tree Canopy • Fall Weather

40. Common Chip Seal Problems

41. Rules of Thumb for Seal Coats • Make sure pavement is clean • Use high quality materials • Proper application rate for binder • Proper application rate for aggregates. Extra aggregates only cause failure. • Keep distance between the distributor and the chipper to minimum. Aggregate must be placed before emulsion starts to break.

42. Rules of Thumb for Seal Coats, cont. • Minimum of three rollers. Keep speed under 5 mph. Compaction must be completed before emulsion is broken. • Final sweeping of roadway as soon as possible. No later then the next morning. • Remember that Details count.

43. Questions? Chip Seals