International Concrete Crosstie & Fastening System Symposium Urbana, IL 6-8 June 2012

1. Investigation of the Mechanics of Rail Seat Deterioration (RSD) and Methods to Improve the Abrasion Resistance of Concrete Sleepers International Concrete Crosstie & Fastening System Symposium Urbana, IL 6-8 June 2012 Ryan G. Kernes, Amogh A. Shurpali, J. Riley Edwards, Marcus S. Dersch, David A. Lange, and Christopher P.L. Barkan

2. Outline • Objectives • Rail seat deterioration (RSD) background • Large scale abrasion test • Evaluation of frictional properties • Small scale abrasion resistance test • Results • Conclusions and future work

3. Objectives • Understand the mechanics of the most critical failure modes • Investigate parameters that affect abrasion mechanism • Characterize frictional forces between rail seat and rail pad • Propose methods of mitigating the critical failure modes • Quantify abrasion resistance of various concrete mix designs, curing conditions, and surface treatments

4. Rail Seat Deterioration (RSD) • Degradation of concrete material under rail and pad • Increases maintenance costs • Shortens service life of the concrete crosstie • Leads to track geometry defects • Feasible mechanisms: • Abrasion • Crushing • Freeze-thaw damage • Hydro-abrasive erosion • Hydraulic pressure cracking

5. Abrasion Mechanism of RSD • Abrasion is a progressive failure mechanism that occurs when: • Frictional forces act between two surfaces in contact • Relative movement occurs between the surfaces • Harder surface cuts or ploughs into softer surface • Progression of abrasion at the rail seat • Cyclic motion of rail base induces shear forces • Shear forces overcome static friction • Pad slips relative to concrete • Strain is imparted on concrete matrix • Abrasion involves 3-body wear: two interacting surfaces (rail pad and rail seat) and abrasive slurry (water and fines)

6. Large Scale Abrasion Resistance Test Experimental Setup Vertical Actuator Abrasion Pad Horizontal Actuator Concrete Specimen

7. Large Scale Abrasion Resistance Test Results • Consistently able to cause deterioration of concrete due to abrasion • Concrete deterioration initiates near pad edges and propagates inward • Heat build up in pad materials at local contact points leads to softening and adhesion to concrete surface • Difficulty in correlating severity of abrasion to input variables • Contact angle and pressure distribution • Heterogeneity of concrete surface

8. Experimental Evaluation of Friction • Magnitude of static frictional force is directly related to the normal force between the two bodies by the coefficient of friction (μ) • Experimental frictional coefficient measured during test calculated by: μ = |𝑭|/𝑷 • where F is the force required to initiate lateral sliding under vertical normal load P • 400 loading cycles to simulate single unit train pass • 5,000 pound normal vertical load (420 psi), 1/8” lateral displacement, 3 cycles/second, no abrasive fines or water added

9. Mean Coefficient of Friction per Loading Cycle Polyurethane Nylon 6/6

10. Effect of Environmental Conditions on Nylon 6/6

11. Effect of Environmental Conditions on Concrete Abrasion Polished surface with no sand Abrasion initiated with sand

12. Effect of Increasing Normal Load on Nylon 6/6 3 kips 5 kips 10 kips

13. Small Scale Abrasion Resistance Test (SSART): Test Setup • In general, similar to other standard abrasion tests • Consists of powered rotating steel wheel with 3 lapping rings • Lapping rings permitted to rotate about their own axis • Vertical load applied using the dead weights • Abrasive sand and water dispensed during testing

14. Test Protocol • Each test can evaluate 3 specimens • Multiple tests are run to evaluate more than 3 specimens • Specimen dimensions: 4 inch (diameter),1 inch (thickness) • Duration: 120 minutes • Wear depth measurements taken every 20 minutes • Speed: 60 revolutions per minute • Abrasive fine: Ottawa 20-30 sand Before After

15. Test Variables • Admixtures • Silica fume: 5%,10% • Fly ash: 15%, 30% • Curing Condition • Moist • Submerged • Oven dry • Air • Surface Treatment • UV epoxy • Polyurethane • Grinding • Fiber Reinforced Concrete (FRC) • Polyurethane • Steel

16. Effect of Mineral Admixtures

17. Effect of Fiber Reinforcement

18. Effect of Curing Conditions

19. Comparison of Techniques to Increase Abrasion Resistance

20. Additional Tests Conducted • Objective: to obtain specimens batched by industry concrete crosstie suppliers • Silica fume and epoxy coated specimens tested • Saw-cut surface of control specimens considered analogous to ground surface and tested Grinding Epoxy coating

21. Effect of Surface Treatments

22. Conclusions • Large scale testing: • Confirmation of abrasion as a feasible RSD mechanism • Frictional coefficient is affected by temperature, water, sand, normal force • SSART: • Successfully compared 13 approaches to improving abrasion resistance of rail seat through material improvements • Improve abrasion resistance of concrete with: • Optimal amounts of fly ash • Proper curing condition • Addition of steel fibers • Grinding cement paste

23. Future Work • Determining the optimal frictional properties at each interface of multi-layer rail pads (top, bottom, and between layers) could: • Reduce movement at critical interfaces • Influence load path and location of slip • Delay the onset of abrasive wear and extend rail seat life • Extend to other fastening system components • SSART: • Perform image analysis to characterize the role of coarse aggregate in abrasion resistance • Study the effect of air entrainment and quality of aggregates on abrasion resistance of rail seat • Use of Statistical Analysis Software (SAS) to model abrasive wear of concrete specimens • Optimize concrete mix design and surface treatments to mitigate abrasion

24. Acknowledgements • Funding for this research has been provided by • Association of American Railroads Technology Scanning Program • NEXTRANS Region V Transportation Center • Eisenhower Graduate Fellowship • For providing direction, advice, and resources: • Amsted Rail - Amsted RPS: Jose Mediavilla, Dave Bowman, Brent Wilson, • BNSF Railway: John Bosshart, Tom Brueske, Hank Lees • AREMA Committee 30: WinfredBoesterling,Pelle Duong, Kevin Hicks, Tim Johns, Steve Mattson, Jim Parsley, Michael Steidl, Fabian Weber, John Zeman • TTCI: Dave Davis, Richard Reiff • Pandrol Track Systems: Bob Coats, Scott Tripple • UIUC: Tim Prunkard, Mauricio Gutierrez, Don Marrow, Darold Marrow • For assisting with the research and lab work: • Josh Brickman, Ryan Feeney, Kris Gustafson, Steven Jastrzebski, Andrew Kimmle, Calvin Nutt, Chris Rapp, AmoghShurpali, Emily Van Dam, Michael Wnek

25. Questions Ryan Kernes Research Engineer Rail Transportation and Engineering Center - RailTECemail: rkernes2@illinois.edu Amogh A. Shurpali Graduate Research Assistant Rail Transportation and Engineering Center - RailTECemail: ashurpa2@illinois.edu