Effect of Matric Suction on Resilient Modulus of Compacted Recycled Pavement Material Kongrat Nokkaew (Presenter) James M. Tinjum, Tuncer B. Edil Mid-Continent Transportation Research Symposium 2013

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 Slide No. 2 University of Wisconsin-Madison

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 Slide No. 3 University of Wisconsin-Madison

Mid-Continent Transportation Research Symposium 2013 Slide No. 4 University of Wisconsin-Madison Unsaturated Zone Saturated Zone Ground water table “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 Slide No. 5 University of Wisconsin-Madison Soil-Water Characteristic Curves (SWCC) aa  A relationship between soil suction and volumetric moisture content/degree of saturation  Matric Suction = negative pore water pressure (U a – U w ) Air entry pressure Residual volumetric water content Soil Particle Menisci water

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

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

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

SWCC fitting equation used in M-EPDG Mid-Continent Transportation Research Symposium 2013 Slide No. 9 University of Wisconsin-Madison

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

Materials PropertiesRPM-MI Limestone- WI USCS designationGWGP-GM AASHTO designationA-1-bA-1-a Unit weight (kN/m 3 ) Water content (opt) (%) Percent absorption Basic properties and soil Classification Grain size distributions Mid-Continent Transportation Research Symposium 2013 Slide No. 11 University of Wisconsin-Madison Limestone-WIRPM-MI

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

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

Mid-Continent Transportation Research Symposium 2013 Slide No. 14 University of Wisconsin-Madison M r test with suction control (Cont.’) Outflow Column Material preparation:  Type I material (150 mm in diameters and 305 mm in height)  Prepared at optimum w n and 95% of  d (modified Proctor effort) Suction conditioning   supplied by vacuum aspirator   verification by checking the equilibrium outflow water 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)

Mid-Continent Transportation Research Symposium 2013 Slide No. 15 University of Wisconsin-Madison Proposed resilient modulus model M r prediction for unsaturated base course (Liang et al. 2008) where (Khalili and Khabbaz 1998)

Proposed resilient modulus model (Cont.’) assumed that Mid-Continent Transportation Research Symposium 2013 Slide No. 16 University of Wisconsin-Madison (Vanapalli and Fredlund 2000)

Mid-Continent Transportation Research Symposium 2013 Slide No. 17 University of Wisconsin-Madison SWCC of studied material fitted with Fredlund and Xing (1994) Model Results  Unimodal SWCC for RPM-MI, bimodal SWCC for Limestone-WI   a < 1kPa  SWCC predicted from M-EPDG:  Low  a (< 0.6 kPa)  Rapidly drop of slope when  a  Low  r (> 10 kPa)

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

Mid-Continent Transportation Research Symposium 2013 Slide No. 19 University of Wisconsin-Madison R 2 = 0.90 RPM-MI SRM versus matric suction  Tested at  = 1.5 kPa, 10 kPa, 20 kPa, 40 kPa, and 65 kPa RPM-MI: SRM 216 – 290 MPa Limestone-WI: SRM 75 – 191 MPa

Mid-Continent Transportation Research Symposium 2013 Slide No. 20 University of Wisconsin-Madison SRM versus matric suction fitted to the M-EPDG prediction  Change as  corresponding to SWCC  Start to increase rapidly when  a  Tend to constant when  a  SRM res /`SRM sat = 3.7 (both materials)  SRM M-EPDG /`SRM measured :  1.9 – 2.9 for RPM-MI  1.7 – 4.2 for DGA-WI SRM predicted from the M-EPDG Equation:

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

Mid-Continent Transportation Research Symposium 2013 Slide No. 22 University of Wisconsin-Madison Conclusions  RPM-MI provides higher SRM than limestone-WI  SRM increases as matric suction increase  The proposed model fits the test results well (R 2 = 0.93) over the full range of studied suction  SRMs predicted from M-EPDG are not conservative during measured range of  (1 – 100 kPa)

Mid-Continent Transportation Research Symposium 2013 Slide No. 23 University of Wisconsin-Madison References

Mid-Continent Transportation Research Symposium 2013 Slide No. 24 University of Wisconsin-Madison Acknowledgements  James Tinjum (Advisor)  Tuncer Edil (Dissertation Committee)  William Likos (Dissertation Committee)  Benjamin Tanko (Undergraduate Assistant)  The Solid Waste Research Program (UW-Madison)  Recycled Materials Resource Center-3 rd Generations  The Royal Thai Government  GeoFriends  Especically Xiadong Wang, Mababa Diagne, Ryan Shedivy and Jiannan Chen

Questions ?

Mid-Continent Transportation Research Symposium 2013 Slide No. 26 University of Wisconsin-Madison Verification of equilibrium time for soil suction conditioning for an applied suction of 10 kPa. Verification of equilibrium time for soil suction conditioning

Mid-Continent Transportation Research Symposium 2013 Slide No. 27 University of Wisconsin-Madison Plastic strain at varying matric suction 1 st Load sequence (Conditioning sequence) 2 nd to 31 st Load sequence

Mid-Continent Transportation Research Symposium 2013 Slide No. 28 University of Wisconsin-Madison Effect of bulk stress and octahedron shear stress on M r M r - bulk stress M r - Octahedron shear stress  Results from RPM-MI at  10 kPa  Measured M r fitted with NCHRP 1-37A equation

Unsaturated soil behavior.terragis.bees.unsw.edu.au/terraGIS_soil Soil Particle Menisci water Total suction = Matric Suction + Osmotic Suction Matric Suction = U a - U w Negligible Mid-Continent Transportation Research Symposium 2013 Slide No. 29 University of Wisconsin-Madison