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Thin LAY Asphalt for Pavement Preservation Tone Garrett Executive Director Mississippi Asphalt Pavement Association.

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Presentation on theme: "Thin LAY Asphalt for Pavement Preservation Tone Garrett Executive Director Mississippi Asphalt Pavement Association."— Presentation transcript:

1 Thin LAY Asphalt for Pavement Preservation Tone Garrett Executive Director Mississippi Asphalt Pavement Association

2 Too Much Month At The End Of The Money Now more than ever we are expected to do more with less. We don’t have the funding to maintain roads we have, much less build new ones. Traffic is still increasing No Quick Fix on the Horizon

3 Objective What is Thin Lay Asphalt? Why Thin Lay Asphalt? Where Thin Lay Asphalt?

4 Why Thin Lay Asphalt? Funding Crisis – Escalating Construction Costs – Declining Revenues – Increasing Regulations – More Miles To Maintain Construction Cost Revenue Time Dollars Fewer Road Miles Less New Construction Lawyers behind every tree

5 Current Overlay Practice = Never Catch UP Example - Lane miles in MDOT Dist. 1= 5, % of these or 1,405 lane miles are shown in Poor or Very Poor Condition. It would cost over $141 million to do a typical overlay on this 26.2 % Current Funding Level is about $18 million per year. So it will take 8 years to overlay the pavements currently in poor condition.

6 The Opportunity Focus nationwide has shifted from construction to preservation Lane miles increased only 8% The value of our National highway and road system estimated at $1.75 trillion Preservation of the system will dominate future expenditures

7 The Opportunity Map 21 moves the nation to performance management Agencies will be required to track and report pavement condition Smoothness will be an important element in the condition rating

8 Opportunity/Threat Agencies are looking at new ways to extend their preservation $$ Have developed a 1R (pave mainly) program In Mississippi for the first time the DOT is increasing chip seals in their Preservation program at the expense of asphalt overlays

9 What about thinlay asphalt? We have promoted thin lifts for many years Have had our successes Many states have made inroads with thin lifts Ohio’s Smoothseal for example In Mississippi with the help of MDOT we have had a good experience

10 We have a great message We do everything the seal treatments do + We improve smoothness We last longer We add structure We’re faster We’re quieter The public prefers asphalt to chip and slurry seals

11 So why aren’t we dominating the market? First cost often dominates the decision process Pavement managers have to cover specific numbers of miles annually with available $

12 So why aren’t we dominating the market? Common Condition rating systems do not recognize the added benefits provided by smoother treatments or treatments that add structure We have not done a good job of quantifying the cost and structural benefits

13 3 Key Messages Performance benefits Structural benefits Cost benefits

14 Time or Traffic Pavement Condition Preventive Maintenance Preventive Maintenance

15 Condition Rating Systems Pavement Condition Index (PCI) is a measure of visual surface distress “only” Most thin treatments therefore only address surface distress Most thin treatments do not improve ride and some actually reduce ride quality

16 Accumulated Traffic Over Life of Pavement Present Serviceability Index (PSI) 0 Preventive maintenance treatments differ widely in their ability to improve serviceability. (Very Good) (Very Poor) 5.0 Lowest acceptable level of serviceability (Terminal Serviceability) Treatments that both repair pavement distresses and improve pavement profile can restore serviceability to new pavement levels.

17 Accumulated Traffic Over Life of Pavement Present Serviceability Index (PSI) 0 Preventive maintenance treatments differ widely in their ability to improve serviceability. (Very Good) (Very Poor) 5.0 Lowest acceptable level of serviceability (Terminal Serviceability) Treatments that primarily repair pavement distresses without improvement to pavement profile have minimal effect on serviceability.

18 Accumulated Traffic Over Life of Pavement Present Serviceability Index (PSI) 0 Preventive maintenance treatments differ widely in their ability to improve serviceability. (Very Good) (Very Poor) 5.0 Lowest acceptable level of serviceability (Terminal Serviceability) Performance more typical of ThinLay asphalt applications.

19 Structural Benefits Preventive Maintenance treatments are supposed to be non-structural Slurry seals, Chips Seals, micro sufacing add no structure A 1/2 to 1 inch asphalt overlay does and should be recognized and credited

20 Structural Benefits Most pavements designed for 20 years with AASHTO design They have finite bottom up fatigue life

21 Structural Benefits A seal type treatment applied on those pavements will have no impact on the tensile strain

22 Structural Benefits Preventive seals on pavements will only mask the impending structural distresses and eventually lead to full depth failures

23

24 Timely thin overlays “Thinlays” can save your structure

25 Thickness Micro strain Reps to failure 2”-65230,234 3”-49571,537 4” ,693 5” ,507 6” ,133 What’s in an inch? Asphalt Thickness VS. Fatigue Life

26 Structural contribution of 1” A 1 inch overlay of an existing 4 inch pavement will double the fatigue life Once you achieve a perpetual design thickness you can focus on managing at the surface for functional attributes as your structural worries are over

27 Perpetual 1” at a time Thin overlays add up and can get you there Here is a simple example You have an existing pavement 4 inches thick designed for 20 years so at year 10 you have consumed 50% of its fatigue life

28 Perpetual 1” at a time If you apply a chip seal at year 10 the strain at the bottom is unchanged and fatigue consumption will continue at the same rate The pavement will develop full depth cracking over the next 10 years, roughness will increase and full depth repairs will be required

29 Perpetual 1” at a time Alternatively if you apply a 1 inch overlay at year 10 you reduce the strain and extend the fatigue life to near 40 years (5 inch pavement has double the fatigue life of a 4 inch pavement) You now have only used up 25% of the life instead of 50% A second 1 inch overlay at year would further extend the fatigue life to beyond 50 years

30 Initial Costs

31 Economics of Preventive Maintenance Treatments

32 Cost Comparison. Thin Lift Overlay = $2.53 per square yard Micro-Surfacing = $1.92 per square yard 32% cost increase

33 Life Cycle Costs 20 Years, I=4%, assume thinlay =10 year life Average micro surfacing life = 5 years Thinlay = $5.82 Micro Surface = $8.20 Thinlay Saves $2.38/yd 2 in 20 Years, adds structure, and provides high serviceability

34 Life

35 Structure?

36 Look Familiar?

37 Pavement Preservation?

38 WE CAN’T GO BACK EVEN IF WE WANTED TO!

39 The Idea Whose Time Has Come

40 Jones County ¾”

41 Mix Design Requirements Sieve SizePercent Passing 1/2 inch100 3/8 inch No. 475 min No No.16-- No ASTM C1252 Fine aggregate angularity of 40 or greater. Up to 30% rap may be used which must be separated on a ½ inch screen. Gradation

42 What Is Thin Lay Asphalt?

43 Mixture Gradation between 9.5 mm and 4.75 mm – Allows Producer to adjust Nominal Maximum Size to allow use of available/economical materials Air Voids – Between 4% and 6% – Allows Designer to adjust/lower asphalt content while maintaining a “tight” impermeable mixture RAP – Allowed up to 25% – Allows Designer to reduce the virgin binder added to the mixture Sand – Allowed up to 30% – Allows additional sand – most economical aggregate General Mixture Specifications

44 Lift Thickness – Specified between ½” to 1” – Allows for economy – Less Mixture Tons per Mile Single Lift Overlay – Used as a Preventative Maintenance Technique – Spot Pre-Leveling and Repair of Structurally Deficient Areas Required Density Requirement – Monitored Roll to Refusal – Rolling Pattern Established by Nuclear Gauge Smoothness – Slight Improvement Expected – As good or better than previous pavement surface General Construction Specifications

45 MDOT Test Locations Route/ County Approx. Length AADT Design Thickness Theo. Tons HMA Actual Tons HMA Square Yards of Pavement Placed SR 370 Lee/Prentiss 1.5 Miles 1200¾ inch SR 370 / Itawamba 2.9 Miles 1000½ inch SR 371 / Prentiss 1.1 Miles inch

46 SR 370 Lee/Prentiss ¾ Inch 36 Months Before

47 SR 370 Lee/Prentiss ¾ Inch 36 Months Before

48 SR 370 Lee/Prentiss ¾ Inch 6 Months 36 Months Before

49 SR 371 Prentiss 1 Inch 6 Month24 Month Before

50 SR 371 Prentiss 1 Inch 6 Month36 Months Before

51 SR 371 Prentiss 1 Inch After 36 Months Before

52 SR 370 Itawamba 1/2 Inch 6 Month 36 Months Before

53 SR 370 Itawamba 1/2 Inch 6 Months 36 Months Before

54 SR 370 Itawamba 1/2 Inch 6 Month Before 36 Months

55 SR 370 Itawamba 1/2 Inch 6 Months 36 Months Before

56 SR 370 Itawamba 1/2 Inch 6 Month Before 36 Months

57 Preservation Comparisons Thin Lay MicrosurfaceSlurry SealChip Seal Corrects Surface Distress√√√√ Increase Skid Resistance√√√√ Minimizes Curb Loss√√√√ Can Be Applied In One Pass√√√√ Eliminates Loose Aggregate√√ Corrects Minor Rutting√ Minimizes Delamination√ Improves Ride Quality√ Increases Structural Strength√ Improves Pavement Drainage√

58 Why Thin Lay Asphalt? Cost Comparison – Typical Overlay to ThinLay Overlay – Assume $70 / mixture Ton – Assume 110 lbs./yd 2 /in. Cost Per yd 2 Per Year Assuming 10 Life ” Thin 1” Thin ¾” Thin ½” $40,656 $27,104 $20,328 $13,552 Lane Mile $0.64 $0.42 $0.32 $0.21 Square Yard 0% 33% 50% 67% Savings

59 Why Thin Lay Asphalt? Life Cycle Cost of Thin Lay Maintenance Treatments – Higher Initial Cost?? – Can be offset by Thinner Lifts – Cost/Square Yard/Year Asphalt Mixture with 10 year Design Life

60 Why Thin Lay Asphalt? Improved Ride – Improved Smoothness – Less Road Noise Public Perception – Freshly Paved Road – New Road – No Broken Windshields Benefits to the Traveling Public

61 Why Thin Lay Asphalt? Concept of Pavement Preservation

62 Where Thin Lay Asphalt?

63 S2S3S6 NCAT Mississippi Test Sections

64 Where Thin Lay Asphalt? Low Volume ST Routes (3 Digit Roads) - City Streets – County Roads

65 Special Thanks I could not have made this presentation without help from: – James Williams – Deputy Chief Engineer, MDOT – Mark Holly – 1 st District Engineer, MDOT

66 Thinlay Asphalt Safe, Smooth, Sustainable Longest Life of all treatments Lowest life cycle cost Superior Smoothness Preferred by road users Maintains Structural integrity Thank You!!

67 Questions Remember that the only stupid question is the one that goes unasked.


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