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Effect of Matric Suction on Resilient Modulus of Compacted Recycled Pavement Material

Effect of Matric Suction on Resilient Modulus of Compacted Recycled Pavement Material. Kongrat Nokkaew (Presenter) James M. Tinjum , Tuncer B. Edil. Research Motivations. Recycled pavement m aterial (RPM) crushed asphalt surface mixed with underlying base course

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Effect of Matric Suction on Resilient Modulus of Compacted Recycled Pavement Material

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  1. Effect of Matric Suction on Resilient Modulus of Compacted Recycled Pavement Material KongratNokkaew(Presenter) James M. Tinjum, TuncerB. Edil Mid-Continent Transportation Research Symposium 2013

  2. Research Motivations Recycled pavement material (RPM) crushed asphalt surface mixed with underlying base course (i.e. subgrade and subbase) • Advantages • Excellent mechanical properties • (e.g. high modulus, low moisture susceptibility) • Life-cycle benefit • (e.g. low transportation needs, no landfill cost) • Environment-friendly • (reducing green house gas emissions, energy • and natural aggregate consumption) Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 2

  3. Premature failure due to moisture in base layer • Base course: • Moisture increases,modulus decreases • Few studies on modulus-moisture for RPM Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 3

  4. Unsaturated Zone • Ground water table • Saturated Zone “Pavements are compacted near optimum water content unsaturated, and place above the ground water table. As a result, Pavement are unsaturated most of service life” Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 4

  5. Soil-Water Characteristic Curves (SWCC) Soil Particle • A relationship between soil suction and volumetric moisture content/degree of saturation • Matric Suction = negative pore water pressure (Ua – Uw) Menisci water Residual volumetric water content ya Air entry pressure Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 5

  6. Impact of moisture on Mr in the Mechanistic- Empirical Design Guide (M-EPDG) • Adjusting factor determined from degree at optimum degree • of saturation Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 6

  7. Objectives • To evaluate the influence of matric suction on Mr for compacted RPM in comparison to conventional crushed limestone • To established amodel for predicting Mr from matric suction and the soil-water characteristic curve (SWCC) • To compare Mr from proposed model to those from M-EPDG equation Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 7

  8. Background Resilient modulus (Mr) • Primary input for Mechanistic-Empirical Pavement Design • Guide (M-EPDG) • Impact to all quality and performance of pavement Where, d : deviatoric stress r: recoverable strain Summary resilient modulus (SRM) • Mr representing stress state in the filed Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 8

  9. SWCC fitting equation used in M-EPDG where = effective degree of saturation = degree of saturation; = residual degree of saturation; is soil suction; , , , and are fitting parameters; and is the base of the natural logarithm Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 9

  10. SWCC parameters estimated by the M-EPDG equation where d60 is particle size in mm at percent finer 60% • SWCC parameter estimated based on d60 • Parameter n: fixed at 7.5 Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 10

  11. Materials RPM-MI Limestone-WI Basic properties and soil Classification Grain size distributions Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 11

  12. Methods Hanging column test Large-scale testing cell (305 mm x 76 mm) Vacuum aspirator (y, 25 - 80 kPa) • Large-scale testing cell • Matric suction: • Hanging column (y, 0.05 to 25 kPa) • Air aspirator (y, 25 to 80 kPa) Hanging column (y, 0.05 - 25 kPa) Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 12

  13. Mrtest with suction control Specimen • Test performed according to NCHRP 1-37A Procedure Ia Modified Bottom Platen-with ceramic plate Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 13

  14. Mr test with suction control (Cont.’) • Material preparation: • Type I material (150 mm in diameters and 305 mm in height) • Prepared at optimum wnand 95% of rd(modified Proctor effort) • Sample saturation: • To remove residual suction from sample compaction • Assumed to be saturated when K is constant and outflow • is more than 3 pore volume of flow (PVF) • Suction conditioning • ysupplied by vacuum aspirator • yverification by checking the equilibrium outflow water Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 14 Outflow Column

  15. Proposed resilient modulus model Mr prediction for unsaturated base course (Liang et al. 2008) (Khalili and Khabbaz 1998) , , = fitting parameters; = matric suction; =atmospheric pressure (101 kPa); =bulk stress; and =octahedral shear stress; is Bishop’s effective stress parameter where Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 15

  16. Proposed resilient modulus model (Cont.’) (Vanapalli and Fredlund 2000) assumed that where = effective degree of saturation = fitting parameter; =degree of saturation; =residual degree of saturation For summary resilient modulus ( = 208 kPa and = 48.6 kPa). Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 16

  17. Results SWCC of studied material fitted with Fredlund and Xing (1994) Model • Unimodal SWCC for RPM-MI, bimodal SWCC for Limestone-WI • ya < 1kPa • SWCC predicted from M-EPDG: • Low ya (< 0.6 kPa) • Rapidlydrop of slope when y > ya • Lowyr (> 10 kPa) Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 17

  18. Relationship between degree of saturation and Mr SRM decrease as degree of saturation increase Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 18

  19. SRM versus matric suction RPM-MI: SRM 216 – 290 MPa R2 = 0.90 RPM-MI Limestone-WI: SRM 75 – 191 MPa • Tested at y =1.5 kPa, 10 kPa, 20 kPa, 40 kPa, and 65 kPa Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 19

  20. SRM versus matric suction fitted to the M-EPDG prediction SRM predicted from the M-EPDG Equation: • Change as y corresponding to SWCC • Start to increase rapidly • when y > ya • Tend to constant when y > ya • SRMres/`SRMsat= 3.7 (both materials) • SRMM-EPDG/`SRMmeasured: • 1.9 – 2.9 for RPM-MI • 1.7 – 4.2 for DGA-WI Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 20

  21. Variation of measured and predicted SRM Comparison between predicted versus measured SRM using proposed modelin comparison to Liang et al. (2008) and M-EPDG Equation Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 21

  22. Conclusions • RPM-MI provides higher SRM than limestone-WI • SRM increases as matric suction increase • The proposed model fitsthe test results well (R2 = 0.93) over the full range of studied suction • SRMs predicted from M-EPDG are not conservative during measured range of y (1 – 100 kPa) Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 22

  23. References • Liang, R.Y., Rabab’ah, H., and Khasawneh, M. Predicting Moisture-Dependent Resilient Modulus of Cohesive Soils Using Soil Suction Concept. Journal of Transportation Engineering, Vol. 134, No. 1, 2008, pp. 34-40. • Vanapalli, S.K., and Fredlund, D.G. Comparison of Different Procedures to Predict Unsaturated Soil Shear Strength. Proc., of Sessions of Geo-Denver 2000, Advances in Unsaturated Geotechnics, ASCE, Reston, VA, 195-209. • Guide for Mechnistic-Empirical Design for New and Rehabilitated Pavement Structure. Final Report, 2004, NCHRP Project 1-37-A. www.trb.org/mepdg/guide.html. Accessed July 23, 2013. • Khalili, N., and Khabbaz, M.H. A Unique Relationship for for the Determination of the Shear Strength of Unsaturated Soils. Geotechnique, Vol. 48. No. 5, 1998, pp. 681-687. Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 23

  24. Acknowledgements • James Tinjum (Advisor) • TuncerEdil(Dissertation Committee) • William Likos (Dissertation Committee) • Benjamin Tanko (Undergraduate Assistant) • The Solid Waste Research Program (UW-Madison) • Recycled Materials Resource Center-3rdGenerations • The Royal Thai Government • GeoFriends • EspecicallyXiadong Wang, MababaDiagne, Ryan Shedivy • and Jiannan Chen Mid-Continent Transportation Research Symposium 2013 University of Wisconsin-Madison Slide No. 24

  25. Questions ?

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