Chip Sealing The Nuts and Bolts. Thomas J. Wood Research Project Supervisor MN/DOT

Transcription

1 Chip Sealing The Nuts and Bolts Thomas J. Wood Research Project Supervisor MN/DOT

2 Why do we do Pavement Preservation?

3 The Answer is? To keep new pavements new longer! Is Pavement Preservation Cost Effective Yes But depends on properly constructed projects. How do we know it is Cost Effective? Anecdotal evidence Pavement Management Data Mn/DOT experiences

4 No Maintenance Seal Coated Poly. (Seal Coated) Poly. (No Maintenance) Average SR Seal Coated SR = x x R 2 = No Maint. SR = x x R 2 = Years since BAB Construction

5 Ride: No Preservation With Preservation Ride Quality Index Pavement Age, years

6 Chip Sealing

7 What Is a Chip Seal? Bituminous surface treatment Heavy asphalt binder membrane Followed by aggregate chip

8 Topics! Seal Coat Handbook Chip Seal Design New Pay Items Aggregate Requirements Binders Construction Details Tips

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10 Originally Published in 1997 Two main parts Chapters 1-4 Materials and Design Chapters 5 8 In the Field Has had a pay back ratio of 77 to 1

11 Revised in 2006 What has been updated? 3 new chapters Fog Sealing Chip Sealing for Recreational Trails Frequently Asked Question About Chip Sealing Updated technical information.

12 Seal Coat Design What does this design method do? 1. Gives amount of stone to cover 1 yd² a single stone thick 2. Gives starting binder application rate Starting rate should yield 60 to 70% embedment

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14 Seal Coat Design Summary Design for FA-3 (3/8 inch) chip Without design av. 30 lbs./yd.² Without design av. Binder 0.30 gal./yd.² With design av. 17 lbs./yd.² With design av. Binder 0.36 gal./yd.²

15 Metro FA-3 chip seal Badly pocked, porous, and oxidized 0.42 BINDER APPLICATION RATE (gal/yd 2 ) Slightly pocked, porous, and oxidized Slightly porous, and oxidized Over 2,000 1,000 to 2, to 1, to 500 Under 100 TRAFFIC VOLUME (ADT)

16 Seal Coat Design Summary Designing and properly constructing your Seal Coats you can do more miles with less money with better results.

17 What is too much rock?

18 Pay Items Changes Old pay items Gallon binder Tons of aggregate Encouraged over application of aggregate Waste of money Increased chance of vehicle damage Conflict between Agency personnel and Contractor.

19 Pay Items Changes New Pay Items Gallons or Tons of Binder Square Yard of Chip Seal Applied Encourages proper application of aggregate Eliminates cost over runs Easy inspection Allows inspectors to concentrate on important issues. Reduces conflict between Agency and Contractor

20 Aggregate Requirements

21 Must be clean! Clay free aggregate Why clay free? Coats chip Strong electrical charge. Less then 1% passing #200 Crusher dust Large amount of surface area with impends the bonding of asphalt binder.

22 Durable LAR loss % max. 35% Why? Where the rubber hits the road

23 Crushing 80 % one face crushed.

24 Flakiness index Max. 25% CFLHD DFT 508

25 Flaky Vs. Cubical Aggregates

26 Flat Chips If the seal coat is designed for chips in the wheelpaths: CHIP LOSS CHIP LOSS There is not enough binder in the non-traffic areas to prevent traffic and snow plows from dislodging the chips.

27 Flat Chips If the seal coat is designed for chips in the non- traffic areas: BLEEDING There is too much binder in the wheelpaths after the flat chips lay on their flattest side.

28 Flaky vs. Cubical Aggregate

29 Flakiness Testing Methods New Method Current Method

30 Dense Graded Vs. Single Size!

31 Dense Graded vs. Single Sized PERCENT PASSING SIEVE SIZE, inches dense graded single sized

32 Advantages of Single Sized Agg. Single sized aggregate More uniform height Weighs less per cubic foot 47% passing the # lbs/ft 3 8% passing the # lbs/ft 3 More room for binder Increased Voids

33 Advantages of Single Sized Agg. MM FA-2.5 $22.80 ton dense graded 18.5 pounds / yard needed $0.211 / yard Single size 14.5 pounds / yard needed $0.165 / yard You can pay up to $6.30 a ton more for single sized chip and the total cost per square yard will be the same as dense grade chip.

34 Binders Hot applied Not commonly used in upper Midwest Needs clean dry chips Cut Back Not environmentally acceptable anymore Every 10,000 gallons of cutback place on roadway gives off 1,500 of gasoline or diesel fuel. Emulsions

35 Binders CRS-2p (cationic rapid set polymer mod.). Develops strength in hours instead of days. Can be swept same day. Requires use of clean aggregates. Must place aggregate within 1 min. of binder placement. Eliminates bleeding. Higher softening point. CRS-2 average softening point 108 F CRS-2p average softening point 128 F

36 High Floats Emulsions Good with dirty aggregate Must let skin over if using clean chips. Supposedly has jell structure. Very slow developing strength Similar to Medium Set Cutback. Has been called emulsified cutback.

37 Residual Asphalt Hot applied 100% Cut back 85% Emulsion 67%

38 Construction Details

39 Distributors

40 YES Same Angle NO Different Angles Fans are the same width Fans are different widths

41 Poor Spray Pattern!

42 Proper Spray Pattern!

43 Bar Too High Bar Height Bar Too Low!

44 Bar Too High Bar Too Low

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46 Plugged Nozzle

47 Chip Spreaders

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49 ASTM D

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54 Modify Methods

55 Proper Shot Rate!

56 Proper Binder and Aggregate Rates

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59 Difference in Curing Rates!

60 Plug Gate on Chipper!

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63 Rollers

64 Trucks

65 Brooms

66 Other Issues!

67 Tips for Successful Seal Coat Make sure pavement is clean Use high quality materials Proper application rate for binder Proper application rate for aggregate Excess aggregate only causes failure Extra cost and waste

68 Tips for Successful Seal Coat Minimum distance between distributor & chip spreader Aggregate must be placed before emulsion starts to break Minimum of three rollers; Speed under 5 mph Compaction must be completed before emulsion is broken

69 Tips for Successful Seal Coat Final sweeping of roadway as soon as possible. No later then next morning. Quality does not cost. It pays! Remember that details count.

70 Typical Minnesota Chip Seal!

71 Questions?

72 Thank You!