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1 Welcome to Pavinars! Today s session will begin at: 12:00pm central time Today s topic: Towards zero deaths: What can pavement engineers help? NOTE: If you can t hear any music playing, please make sure the speaker on the top left menu bar of Adobe Connect is checked click and follow the Audio Setup Wizard. Native American Flute & Guitar Album.

2 Special Acknowledgement Pavinars are free webinars for the pavement community initiated by Dr. Andrew Braham at University of Arkansas in years 25 webinars 2

3 Logistics of Pavinars If you have a question Raise your hand by clicking on the hand icon on the top left menu bar. You can type your question into the chat box at the lower-left side of the screen at anytime. PDH hours will be ed to you within one week after the presentation 3

4 Towards zero deaths: What can pavement engineers help? August 5, 2014 Dr. Danny Xiao, Research Associate Louisiana Transportation Research Center Louisiana State University (Image from Towards Zero Deaths: National Strategy on Highway Safety, FHWA, 2014)

5 5 What we ll talk about today Background Importance of pavement friction Tools Improve micro-texture Improve macro-texture Case Study I High friction surface treatment (HFST) Case Study II Open graded friction course (OGFC)

6 6 Statistics of Highway Safety 33,561 (Figure from Towards Zero Deaths: National Strategy on Highway Safety, FHWA, 2014) each data point on that chart represents thousands of friends, family members, and colleagues whose lives ended too soon because of a traffic crash.

7 Possible causes of skid-related crashes Weather (wet, night, fog) Human factor (speeding, distraction, alcohol) Roadway geometry (curve, grade, superelevation) Pavement (low friction resistance, hydroplaning) Image from 7

8 Importance of Pavement Friction What is the main cause of fatalities? Speeding? Alcohol? Smart phones? Roadway? Total fatalities = 33,561 (from Towards Zero Deaths: National Strategy on Highway Safety, FHWA, 2014) 70% of wet pavement crashes can be prevented or minimized by improving pavement friction. 8

9 9 Now we ll move from background to tools Background Tools Questions? Please raise your hand and type your question in the chat box.

10 10 Friction and pavement texture Pavement surface texture is defined as the deviations of the pavement surface from a true planar surface. Simplified illustration of the various texture ranges that exist for a given pavement surface (Sandburg, 1998)

11 11 Friction and pavement texture Friction is primarily affected by micro-texture and macro-texture. Texture three zone concept of a wet surface (after Moore, 1966)

12 Tools for pavement engineers Friction management Surface texturing (rigid pavement) Mixture type design (gradation) Select aggregates 12

13 How to select aggregates? Aggregate properties Hardness Mineralogy Shape Texture Angularity Abrasion resistance Polish resistance Soundness Aggregate tests Scratch hardness Petrographic analysis Fractured face particles Uncompacted voids of fine aggregate LA Abrasion Micro-Deval Polish stone value (PSV) Acid insoluble residue Magnesium sulfate soundness No individual test provides a full and accurate prediction of friction performance. 13

14 How to select mixture type? Mixture type Macro-texture depth (MTD, mm) Dense fine-graded HMA 0.4~0.6 Dense coarse-graded HMA 0.6~1.2 Gap-graded HMA or Stone Matrix Asphalt (SMA) Open-graded friction course (OGFC) > ~3.0 Macrotexture Better (Adapted from NCHRP 1-43 final report: Guide for Pavement Friction, TRB, 2009) 14

15 Micro-texture Combination of micro- and macro- texture Different micro- and macro- textures could be combined to achieve the desired friction level. Macro-texture Friction (Graph from NCHRP 1-43 final report: Guide for Pavement Friction, TRB, 2009) 15

16 16 Now we ll move to case study I Background Tools Case Study I Questions? Please raise your hand and type your question in the chat box.

17 Select aggregate: High Friction Surface Treatment (HFST) HFST are pavement surface treatments that are composed of extremely hard, polish- and abrasion-resistant aggregates bonded to the pavement surface using a resin or polymer material. (Brimley and Carlson, 2012) 17

18 Select aggregate: High Friction Surface Treatment (HFST) Aggregates: Calcined bauxite, commonly used. (PSV=70) steel slag, granite, basalt (high PSV) Binders Epoxy-Resin Rosin-Ester Polyurethane-Resin Acrylic-Resin (Image: David Merritt) 18

19 Calcined bauxite, epoxy resin Manually installed Skid number: 24 70s Case Study of HFST Pennsylvania Sr 611 Wet weather crashes:

20 20 Case Study of HFST Texas Report Brimley and Carlson, Using High Friction Surface Treatments to Improve Safety at horizontal Curves, 2012 Effectiveness: 20-to 30-percent reduction in all crashes 50-percent reduction in wet-weather crashes Expected Life: 10 years 5 years, a conservative expectation Economic Benefits: Cost of $30,000 (2-lane, 400 ft) may be cost-effective if one crash is prevented per five years.

21 HFST: Technical Questions Where should it be applied? How much does it cost? How long does it last? How to choose candidate sites? What tests should be done on aggregate and binder? How to do quality control? etc. American Traffic Safety Services Association 21

22 22 Now we ll move to case study II Background Tools Case Study I Case Study II Questions? Please raise your hand and type your question in the chat box.

23 Select mixture type: Open-Graded Friction Course (OGFC) Permeable Friction Course (PFC) Providing higher macrotextures quick water drainage better contact between tire and aggregate (microtexture) better safety Texture three zone concept of a wet surface (after Moore, 1966) 23

24 OGFC: Benefits Reduce hydroplaning, improve skid resistance. Smooth wearing layers improve fuel economy Reduce traffic noise (NCHRP 9-41 Report, 2009) Conventional HMA OGFC (Image from Rebecca McDaniel, 2009) 24

25 OGFC: Unique Characteristics Generally, not considered as a structural layer. Stabilizing additives (fibers) to minimize draindown. Only steel wheel rollers are used during construction. A challenging problem is clogging. (NCHRP 9-41 Report, 2009) 25

26 26 Case Study of OGFC Louisiana King, et al., Evaluation of Open Graded Friction Course Mixtures, 2013 Four projects in Louisiana Laboratory tests (permeability, loaded wheel tracker, etc.) Field performance tests (friction, distress)

27 Lab test result Permeability water moves away from the surface less hydroplaning better safety (King et al., 2013) 27

28 Friction Number 28 Field test result Friction test: OGFC has a higher FN OGFC Conventional 0 I-20 US-61 US-171 Test Sections (Graph adapted from King et al., 2013)

29 Benefit: Accident Reduction Reduction in total accidents: 42~100% Reduction in fatalities: 0~100% 29

30 Conclusions from Louisiana Study Louisiana OGFC mixtures are capable of delivering impressive performances as well as providing a safe traveling surface. Five year pavement distress data indicate that the performance and projected life of OGFC sections are comparable to the typical Superpave sections. Based on the outcome of this study, the authors highly recommend the implementation of OGFCs for any roadway surface having wet weather safety concern. (King et al., 2013) 30

31 In Summary 70% of wet pavement crashes can be prevented or minimized by improving pavement friction. Pavement friction is primarily affected by micro-texture and macrotexture. Micro-texture Aggregate Macro-texture Mixture design HFST OGFC 31

32 32 Dare to Dream A friction prediction model in Pavement ME? A better link between laboratory testing and field performance? Virtual mixture design: predict macro-texture based on aggregate properties and gradation?

33 References and links for further information Towards Zero Deaths: National Strategy on Highway Safety, FHWA, 2014 NCHRP 1-43 final report: Guide for Pavement Friction, TRB, 2009 Flintsch et al., The Little Book of Tire Pavement Friction, 2012 FHWA Every Day Counts (EDC) initiatives on HFST American Traffic Safety Services Association NCHRP Synthesis 284, Performance Survey on Open-Graded Friction Course Mixes, TRB, 2000 NCHRP 9-41 final report, Construction and Maintenance Practices for Permeable Friction Courses, TRB, 2009

34 Acknowledgements Dr. Andrew Braham, University of Arkansas Dr. Zhong Wu, Dr. Doc Zhang, Mr. Harold Paul, Louisiana Transportation Research Center Image from

35 35 Disclaimer To the best of my knowledge, all information included in this Pavinar session fall under the fair use or public domain guidelines of copyright law in the United States. All information presented in this session were retrieved from public domains (reports, journal articles, and presentation handouts). While efforts were made to provide references as accuracy as possible, there might be occasions of omission or error. If this is the case, please contact Dr. Danny Xiao at or The opinions expressed in this Pavinar seesion were those of the author, who is responsible for the accuracy of the facts and data herein, and do not necessarily reflect the official policies of any state highway agency, any organization, or any commercial entity.

36 Logistics wrap-up PDH hours will be ed to you within one week after the presentation You can re-watch Pavinars through the website Welcome your comments and suggestions The next Pavinar will be Tuesday, September 2: Improve pavement management system to meet MEPDG's needs 36

37 Towards zero deaths: What can pavement engineers help? Background Tools Case Study I Case Study II Questions? Please raise your hand and type your question in the chat box. 37