ThinLAY Asphalt for Pavement Preservation Tone Garrett Executive Director Mississippi Asphalt Pavement Association 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 Objective • What is ThinLay Asphalt? • Why ThinLay Asphalt? • Where ThinLay Asphalt? Why ThinLay Asphalt? • Funding Crisis Escalating Construction Costs Declining Revenues Increasing Regulations More Miles To Maintain Dollars – – – – Revenue Time Fewer Road Miles Less New Construction Current Overlay Practice = Never Catch UP Example - Lane miles in MDOT Dist. 1= 5,399 26.2 % 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. The Opportunity • Focus nationwide has shifted from construction to preservation • Lane miles increased only 8% 1980-2009 • The value of our National highway and road system estimated at $1.75 trillion • Preservation of the system will dominate future expenditures 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 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 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 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 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 $ 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 3 Key Messages • Performance benefits • Structural benefits • Cost benefits Preventive Maintenance Pavement Condition Preventive Maintenance Time or Traffic 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 Present Serviceability Index (PSI) (Very Good) 5.0 (Very Poor) Treatments that both repair pavement distresses and improve pavement profile can restore serviceability to new pavement levels. Lowest acceptable level of serviceability (Terminal Serviceability) 0 Accumulated Traffic Over Life of Pavement Preventive maintenance treatments differ widely in their ability to improve serviceability. Present Serviceability Index (PSI) (Very Good) 5.0 (Very Poor) Treatments that primarily repair pavement distresses without improvement to pavement profile have minimal effect on serviceability. Lowest acceptable level of serviceability (Terminal Serviceability) 0 Accumulated Traffic Over Life of Pavement Preventive maintenance treatments differ widely in their ability to improve serviceability. Present Serviceability Index (PSI) (Very Good) 5.0 (Very Poor) Performance more typical of ThinLay asphalt applications. Lowest acceptable level of serviceability (Terminal Serviceability) 0 Accumulated Traffic Over Life of Pavement Preventive maintenance treatments differ widely in their ability to improve serviceability. 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 Structural Benefits • Most pavements designed for 20 years with AASHTO design • They have finite bottom up fatigue life TENSILE STRAIN Structural Benefits • A seal type treatment applied on those pavements will have no impact on the tensile strain TENSILE STRAIN Structural Benefits • Preventive seals on pavements will only mask the impending structural distresses and eventually lead to full depth failures Timely thin overlays “Thinlays” can save your structure What’s in an inch? Asphalt Thickness VS. Fatigue Life Thickness Micro strain Reps to failure 2” -652 30,234 3” -495 71,537 4” -383 160,693 5” -302 340,507 6” -242 682,133 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 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 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 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 20-25 would further extend the fatigue life to beyond 50 years Initial Costs Economics of Preventive Maintenance Treatments Cost Comparison. • Thin Lift Overlay = $2.53 per square yard • Micro-Surfacing = $1.92 per square yard • 32% cost increase 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/yd2 in 20 Years, adds structure, and provides high serviceability Annualized Cost per SY (OHIO data) - no discount (Based on Ave. Years Between Treatment) (Sep 16 '10 to Sep 20 '12 data) Life 5 $0.37 Microsurfacing (surface crse.) 4 $0.40 Single Chip Seal w/polymer 9 $0.52 AC Surface, Type 1 (1.25" thick) Smoothseal Type B (3/4" thick) Smoothseal Type A (3/4" thick) $- $0.28 13 $0.29 13 $0.20 $0.40 $0.60 Structure? Look Familiar? Pavement Preservation? WE CAN’T GO BACK EVEN IF WE WANTED TO! The Idea Whose Time Has Come Jones County ¾” Mix Design Requirements Gradation Sieve Size 1/2 inch 3/8 inch No. 4 No. 8 No.16 No. 200 Percent Passing 100 95-100 75 min 22-70 -4-12 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. What Is ThinLay Asphalt? General Mixture Specifications • 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 Construction Specifications • 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 MDOT Test Locations AADT Design Thickness Theo. Tons HMA Actual Tons HMA Square Yards of Pavement Placed 1.5 Miles 1200 ¾ inch 938 1144 22745 SR 370 / Itawamba 2.9 Miles 1000 ½ inch 1128 1718 40624 SR 371 / Prentiss 1.1 Miles 1500 1 inch 997 930 17449 Route/ County Approx. Length SR 370 Lee/Prentiss SR 370 Lee/Prentiss ¾ Inch Before 36 Months SR 370 Lee/Prentiss ¾ Inch Before 36 Months SR 370 Lee/Prentiss ¾ Inch Before 6 Months 36 Months SR 371 Prentiss 1 Inch Before 6 Month 24 Month SR 371 Prentiss 1 Inch Before 6 Month 36 Months SR 371 Prentiss 1 Inch Before After 36 Months SR 370 Itawamba 1/2 Inch Before 6 Month 36 Months SR 370 Itawamba 1/2 Inch Before 6 Months 36 Months SR 370 Itawamba 1/2 Inch Before 6 Month 36 Months SR 370 Itawamba 1/2 Inch Before 6 Months 36 Months SR 370 Itawamba 1/2 Inch Before 6 Month 36 Months Preservation Comparisons ThinLay Microsurface Slurry Seal Chip 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 √ Why ThinLay Asphalt? • Cost Comparison – Typical Overlay to ThinLay Overlay – Assume $70 / mixture Ton – Assume 110 lbs./yd2/in. Cost Per yd2 Per Year Assuming 10 Life 9.5 mm @ 1.5” ThinLay @ 1” ThinLay @ ¾” ThinLay @ 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 Why ThinLay Asphalt? • Life Cycle Cost of ThinLay Maintenance Treatments – Higher Initial Cost?? – • Can be offset by Thinner Lifts – Cost/Square Yard/Year • Asphalt Mixture with 10 year Design Life Why ThinLay Asphalt? Benefits to the Traveling Public • Improved Ride – Improved Smoothness – Less Road Noise • Public Perception – Freshly Paved Road – New Road – No Broken Windshields Why ThinLay Asphalt? • Concept of Pavement Preservation Where ThinLay Asphalt? NCAT Mississippi Test Sections S2 S3 S6 Where ThinLay Asphalt? • Low Volume ST Routes (3 Digit Roads) - City Streets – County Roads Special Thanks • I could not have made this presentation without help from: – James Williams – Deputy Chief Engineer, MDOT – Mark Holly – 1st District Engineer, MDOT 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!! Questions • Remember that the only stupid question is the one that goes unasked.