2/9/15 I. What is High Friction Surface Treatment (HFST)? II. Friction Number vs. Skid Number vs. Coefficient of Friction III. Why friction matters? IV. NCAT aggregate durability testing phase I Jesse De Los Santos & Bruce Barrett V. Aggregate cost comparison January 20, 2015 VI. Methods of application VII. Reusing aggregate VIII. Causes of aggregate loss and delamination High Friction Surface Treatment consists of: 1. Calcined Bauxite, the wearing surface aggregate • produced by heating at temperatures of 1650 to1700ºC. • Imported from China and Guyana. Source: Mike Moravec: Senior Highway Engineer Federal Highway Administration 2015 Nebraska Concrete Paving Associaon Workshop 1 2/9/15 2. Polymeric Binder Resin (proprietary mixtures) • Epoxy-resin • Polyester-resin • Polyurethane-resin • Acrylic-resin • Methyl Methacrylate Resin + Hardener →Heat Final Hardened Product Source: “Quest for Calcined Bauxite”, Alison Tran, www.ogneupor-spb.ru/besplatno/2.pdf Table 1. Physical Requirements of the Polymer Binder Resin System Property Test Method Polymer Binder Resin Viscosity ASTM D 2556 7-30 poises NDOR Rotation Gel Time AASHTO M 235 10 minutes min. HFST REQUIREMENTS Compressive ASTM C 579 1000 psi min. Strength*, 3 hr. Compressive ASTM C 579 5000 psi min. Direction of motion Strength*, 7 days Ultimate Tensile AASHTO M 235 @ 73 2500 psi min. Strength deg. F Elongation, at AASHTO M 235 30-70% break point D u r o m e t e r ASTM D 2240 60-80 Friction Force, F Hardness (shore D) Adhesive Strength ASTM D 4541 250 psi min. or 100% @ 24 hr substrate failure F Cure Time, ”Dry ASTM D 1640 3 hrs. max µ = Eq. 1 Through Fw Time” (prior to Table 2: Bauxite Aggregate Requirements traffic) LA Abrasion Test, Maximum 20.0 AASHTO T96 The results of the locked-wheel test are reported as a friction Water Absorption AASHTO M 235 1% max 100% Min. Passing No. 4 *Mixed with aggregate. 95.0 – 100% Passing No. 6 number (FN, or skid number [SN]), which is computed using Aggregate Gradation AASHTO T27 0.0– 5.0% Passing No. 16 the following equation: 0.0 – 1.0% Passing No. 30 Moisture Content, Maximum 0.20% AASHTO T255 FN(V) = 100µ = 100*(F/W) Sodium Sulfate Soundness, 12% AASHTO T104 Maximum Loss Source: 2009 NCHRP: Guide for Pavement Friction Aluminum Oxide Content, 87% NDR C25 Minimum 2015 Nebraska Concrete Paving Associaon Workshop 2 2/9/15 Why Friction Matters Double the Skid Resistance & Halve the Crashes Friction Numbers Decrease with Age and Traffic Use Source: Investigation of Hot Mix Asphalt Surfaced Pavements Skid Resistance in Maryland State Highway Network System, TRB 2006 Annual Meeting, Wenbing Song, et. al. Source: 2009 NCHRP: Guide for Pavement Friction Curves Ramps Bridges Stops Friction Numbers for Portland Concrete using inverted Astro Turf Source: MnRoad, April 2011, Tim Nelson, MnDOT •Demand for friction increases when a driving Skid Numbers for Nebraska’s Newly maneuver changes a vehicle’s speed or direction. Constructed Tined PCC are typically 54. Skid Numbers for Nebraska’s Diamond Grinding •When the demand for friction is greater than the frictional and Texturing Concrete Pavement are typically 46. force provided by the pavement, the potential for a crash increases. 2015 Nebraska Concrete Paving Associaon Workshop 3 2/9/15 Crashes at Horizontal Curves • Roughly 28% of all fatal crashes occurred at horizontal curves. Bikeways source: 2007 National Highway Traffic Safety Administration/Fatality Analysis Reporting System • The average crash rate for horizontal curves it approximately three times the crash rate of tangent sections. EDC- Accelerating Innovation Technologies Deployment and Shortening Project Delivery • Roadway departure crashes that result from crossing the centerline or leaving the traveled way make up 52% of non-intersection fatal crashes. Sidewalks Morganza Spillway Bridge 78,000 gallons of binder resin 3.5 miles long 2.5 Million pounds of HFST aggregate Source: John LeFante Interstate Road Management [email protected] Comparison of Surface Treatments Chip Seals Immediately after Application SN 50-70 at 12 Months SN 44-52 WHAT SKID NUMBERS OR FRICTION NUMBERS CAN WE Failure segments at 12 months SN 20-30 EXPECT FROM HFST? Microsurfacing Immediately after Application SN of 28 to 57 NDORs specification states, “The minimum acceptable Increased at 12 Months SN of 40 to 60 friction number (FN40R) is 65.” Our test procedure is Continuous decline after 12 Months based on ASTM E274. Ultra Thin Bonded Wearing (UTBW) course, initial SN 48 to 59 NDOR skid tests with a locked wheel testing trailer. at 33 Months SN 32 to 39 Dense graded HMA overlays, initial SN 35 to 52 at 12 Months SN 30 to 40 Fog Seals reduce friction by 20 to 33% until they return to the original SN after about 12 months. Source: Shuo Li, Indiana Department of Transportation, Evaluation of Pavement Surface Friction Treatments. Publication FHWA/IN/JTRP-2012/04. Joint Transportation Research Program. 2015 Nebraska Concrete Paving Associaon Workshop 4 2/9/15 NCAT Aggregate Durability Study Phase I Source: David Merritt (Transtec Group), Mike Moravec(FHWA), Mike Heitzman(NCAT), High Friction Surface Treatment Aggregate Durability Study, 9/16/14. Costs: NCAT Aggregate Durability Study Phase I – Test Track High Friction Surface Treatment 1 layer $25/SY Sections Bridge 2 layer $47/SY Epoxy Polymer Overlay (Flint) 2 layer $43/SY Calcined Bauxite, $725/Ton 1 layer $5.43/SY Flint, $200/Ton 1 layer $1.50/SY Additionally the cost of perpetuating HFST every 8 years needs to be taken into consideration. Flint Bauxite Source: David Merritt (Transtec Group), Mike Moravec(FHWA), Mike Heitzman(NCAT), High Friction Surface Treatment Aggregate Durability Study, 9/16/14. 2015 Nebraska Concrete Paving Associaon Workshop 5 2/9/15 NCAT Aggregate Durability Study Phase I – Test Track Sections Source: David Merritt (Transtec Group), Mike Moravec(FHWA), Mike Heitzman(NCAT), High Friction Surface Treatment Aggregate Durability Study, 9/16/14. Vacuum and Sweep to Remove Loose Aggregate Causes of Aggregate Loss • Inadequate depth of resin applied • Inadequate mixing of the binder components • Use of damp aggregate • Foot or vehicular traffic after gelling but prior to curing Causes of Delamination • Surface moisture too high • Improper surface preparation Recovered Calcined Bauxite can be reused if: • Free of debris • Meets gradation & moisture requirements 2015 Nebraska Concrete Paving Associaon Workshop 6 2/9/15 Weather Limitations: PROJECTS Pavement temperatures must be between 60º F and 100º F 2014 77-2(161), BNSF/Middle Creek, CN 13089 10,462 SY 1 layer $25/SY 17779 SY 2 layers $47/SY 275-7(193), Waterloo South, CN 22463 By Change Order 3332 SY 2 Layers, $65/SY 2015 275-7(1044), Waterloo Viaduct Friction Course, CN 22613 47031 SY $17.25/SY 1 layer 680-9(34), SB I680 to EB I80 Ramp, Omaha, CN 22596 10444 SY $20.50/SY 1 layer Jesse De Los Santos & Bruce Barrett January 20, 2015 2015 Nebraska Concrete Paving Associaon Workshop 7 2/9/15 Cramer & Associates – Prime Project Includes HFST Installation • McGill Restoration (Omaha, NE) – Sub-Contractor Bridge Rail Sealing Expansion Joint Repair • Work Performed in 2015 Grade Beam Installation (North End) • Work Performed in 2015 New Approaches (North End) • Work Performed in 2015 HFST installed on Four Structures Overall Lengths on 4-Lane HWY 77 • BNSF Viaduct – 2 Structures Including Shoulders Lengths were approx. 1760’ to 1770’ • SB Approx. 2900’ x 2 Lane • Middle Creek – 2 Structures • NB Approx. 3100’ X 2 Lane Lengths were approx. 350’ Ramps In Addition to Mainline Concrete Pavement • SB HWY 77 Off Ramp to Rosa Parks Way – 430’ Asphaltic Pavement • NB HWY 77 On Ramp from Rosa Parks Way – 615’ 2015 Nebraska Concrete Paving Associaon Workshop 8 2/9/15 Husker Football Summer Heat/Direct Sun Exposure • 4 Home Games In One • Causes Surface Temp to raise above Spec. Month Maximum Surface temp of 100˚F • Off Road 3:00 pm Friday Prior to Home Games • Night Work • Allowed back on Road Cooler Weather 9:00 am following • Temp Can’t drop below 55˚F within 8 hrs. of Sunday placement. Labor Day • Off Road by 3:00 pm Rain/Moisture Friday Before • Any moisture penetrating surface negates • Back on Road Tuesday moisture test, and another will be performed following holiday SB Inside Lane SB Outside Lane and NB Inside Lane • Began Surface Prep on 8/24 • Began Preparing Surface Sunday 9/7 Surface prep during day, HFST installed day and night • Test Strip Installed 8/25 Cooler Temps • Work Called off for week due to rain • Able to work from 9/7 to 9/19 • Labor Day Weekend No Home Football Game • Unable to Begin work until Tuesday 9/2 • Finished remainder of first lane and two additional lanes Surface prep during day, HFST overnight NB Outside Lane High Surface Temps • Began Surface Prep on 9/21 • Off Road on 9/5 Surface prep during day, HFST installed day and night Cooler Temps Home Football Game • Off Road on 9/26 • Finished ¾ length of SB Inside Lane • Finished One Lane 2015 Nebraska Concrete Paving Associaon Workshop 9 2/9/15 Completed Installation of Approximately 28,500 SY of HFST WITHIN 34 DAYS! • Also completed all cleaning and sealing of the rails Minor repairs to HFST were taken care of in one day 1 LAYER 2 LAYER Concrete Pavement Bridge Decks • Short stretches between • BNSF Viaducts BNSF Viaduct and Middle • Middle Creek Bridges Creek Bridges SAFETY of HFST Asphaltic Pavement Seal/Preserve Deck • South of Middle Creek Bridges Main purpose of HFST is to enhance SAFETY 2015 Nebraska Concrete Paving Associaon Workshop 10 2/9/15 Aggregate Shot Blasting • 60 LB sample taken to Central Lab • Slow Process • Tested for Gradation • Up to three machines Sodium Sulfate Soundness operating at a time Aluminum Oxide Content 20” Blast Pattern Difficulty meeting Specification Multiple Passes Signed Certificate of Analysis from Supplier • Removes majority of Epoxy contaminants • 16 oz.