Skid Evaluation of Asphalt Mixes Status and Plans John Zaniewski - PowerPoint PPT Presentation

Skid Evaluation of Asphalt Mixes Status and Plans John Zaniewski Asphalt Technology Professor West Virginia University Asphalt Paving Conference February 2019 1-1

Need for new method for laboratory skid evaluation • WVDOH currently test aggregate – not mixes • Method has been successful • Shortage of availability of aggregates that meet the skid requirements 1-2

Requirements for skid testing in lab a. Sample preparation b. Polishing c. Friction test 1-3

Requirements for skid testing in lab • a. Sample preparation • Slabs Simple • Cylinder • Lab • Field cores • b. Polishing • c. Friction test 1-4

Requirements for skid testing in lab • a. Sample preparation a. Methods (US) • b. Polishing a. NCSU • “rub on the b. NCAT surface to c. Ohio simulate traffic” • c. Friction test 1-5

Requirements for skid testing in lab North Carolina State University a. Polishing Methods Developed in 1970’s (US) Only method with an ASTM a. NCSU standard b. NCAT Not currently used by other c. Ohio agencies 1-6

Requirements for skid testing in lab a. Polishing Methods National Center for Asphalt Tech. (US) • Developed in 2000’s a. NCSU • Most commonly reported b. NCAT method in current literature c. Ohio • Most agencies contract with NCAT for testing 1-7

Requirements for skid testing in lab Akron University for ODOT a. Polishing Methods • Developed in 2000’s (US) • Commercially available a. NCSU • ODOT is implementing b. NCAT • Five contractors have devices c. Ohio 1-8

Requirements for skid testing in lab a. Polishing Methods (US) Cylindrical samples Polish 12 samples per run a. NCSU Selected by DOH Not currently used by other agencies b. NCAT Custom fabrication c. Ohio 1-9

Four applications of tire per revolution 1-10

NCSU polisher in action 1-11

Polishing Co. 1 SP 12.5 skid 8% Cycles 0 2000 8000 1-12

Requirements for skid testing in lab • a. Sample preparation • b. Polishing • c. Friction test British Pendulum Dynamic Friction Meter Circular Track Meter 1-13

• NCSU • British Pendulum Texture Test Friction Test 1-14

BP in action 1-15

Typical results 1-16

65 Shake The polisher is operational. down 60 Hopefully more consistency can be achieved. testing Sample 2 55 British Pendulum Number Sample 3 Sample 5 50 Sample 6 BPN Sample 8 45 Sample 9 Sample 11 Sample 12 40 35 Number of cycles 30 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 Number of Cycles Polished 1-17

Average BPN Trends per Mix Type and Air Void Content After 12000 Polishing Cycles Initial 90.0 Co 1 12.5mm Skid-RAP 8% AC British Pendulum Number testing 85.0 Co 1 12.5mm Skid-RAP 4% AC British Pendulum Number (BPN) 80.0 Looks 75.0 Co 2 W1-RAP 4% AC 70.0 good Co 2 W1-RAP 8% AC 65.0 60.0 48,000 tire 55.0 50.0 applications 45.0 40.0 0 2000 4000 6000 8000 10000 12000 14000 Number of Polishing Cycles Number of cycles 1-18

What does BPN mean? British >65 Good >55 Satisfactory 45 Minimum all sites Virginia 47 Minimum NY 52 Minimum 1-19

Original Research 1967 1-20

Average BPN Trends per Mix Type and Air Void Content After 12000 Polishing Cycles How did 90.0 Co 1 12.5mm Skid-RAP 8% AC British Pendulum Number we do? 85.0 Co 1 12.5mm Skid-RAP 4% AC British Pendulum Number (BPN) 80.0 75.0 Co 2 W1-RAP 4% AC 70.0 Co 2 W1-RAP 8% AC 65.0 60.0 55.0 50.0 VA min 45.0 40.0 0 2000 4000 6000 8000 10000 12000 14000 Number of Polishing Cycles Number of cycles 1-21

How did the “typical results” do? HMM VA min 1-22

Establish Protocol • Friction Polishing • Tires measurements • Pressure • Water application BP • Hardness • Texture measurement? • Tire toe in angle • Number of cycles • Air voids 1-23

Testing program • Evaluation of existing • Compare laboratory to field wearing mixes i. Plant mixes vs lab mixes i. Skid mixes vs nonskid mixes ii. Lab results vs field results ii. 9.5 vs 12.5 iii. 4.75??? Work with DOH and input from industry 1-24

Next • More testing • Compare mix types • Compare aggregate gradations • Compare aggregate types • What do the results mean • Important to compare lab and field results • Existing pavements • New construction 1-25

You can ask questions but… Lets go Herd 1-26