1. Module 2-5 Field Sampling and Testing

2.  Identify reasons for conducting field sampling and lab testing  Describe typical field sampling and testing procedures  Describe laboratory test methods and their applications  Describe the use of field and laboratory test results in rehabilitation design Learning Objectives

3. Reasons for Conducting Field Sampling and Lab Testing  Complement and verify NDT  Absence of NDT  Diagnose causes (mechanisms) of distress  Identify structural characteristics and layer material properties in existing pavement  Economics  Recycling  Emphasis on rehabilitation

4. Typical Field Sampling and Testing Procedures  Material specimen sampling  Coring  Auger  Split-spoon  Shelby (push) tube  Test pit  Field testing  Dynamic cone penetrometer (DCP)  Ground penetrating radar (GPR)?

5. Coring  Widely used method for:  Laboratory test samples  Layer thickness determination (or verification)  Visually characterizing layer material types and conditions  Relatively inexpensive  Coring plans used to assess variability along a project

6. Coring Removing a Core

7. Coring Layer Thickness Verification

8. Coring Distress Cause Identification

9. Coring Sampling Approaches  Uniform spacing, e.g., every 500 m   Based on review of “strip” charts  Distance Along Roadway

10. Coring Sampling Locations and Frequency  Standard location  Outside lane  Outer wheel path  Frequency (no. of samples) depends on:  Variability (uncertainty)  Project size (anticipated rehab cost)  Traffic and safety issues  Typical spacing: 100 to 800 m

11. Dynamic Cone Penetrometer (DCP)  Device for measuring in-situ strength of paving materials and subgrade soils  Correlated to California Bearing Ratio (CBR)

12. Cone angle 60 o Handle Hammer (17.6 lb) Cone Steel rod (0.64 in) 22.6 in 39.4 in (variable) 1 in = 25.4 mm 1 lb = 0.454 kg 0.79 in DCP Device

13. DCP Testing Process

14. Example DCP Results No. of Blows Depth Base HMA Subbase Subgrade Soil

15. Ground Penetrating Radar (GPR) HMA Base Subbase Subgrade Soil GPR Transmitter/Receiver Conceptual Output

16. Laboratory Test Methods and Their Applications  Type of material  Basic property being measured  Material’s state of stress Test methods (and their applications) are dependent upon:

17. Typical Properties Measured in Lab GeneralProperty Various Test Measures Stiffness M R, E*, R-value Strength CBR, indirect tension, unconfined compression Compaction , AVC Constituents , AC, gradation, contaminants Permeabilityk Volume Stability PI, 

18. Resilient Modulus  Surrogate for Young’s (elastic) modulus  Fundamental engineering property  Loading conditions:   E MRMRMRMR  Triaxial compression  Axial compression  Indirect tension

19. Resilient Modulus Test Triaxial Compression Used primarily for testing of unbound materials (re-compacted specimens or push tube samples)

20. Resilient Modulus Method of Determination Strain,  Deviator Stress,  D Plastic Strain Resilient Strain Total Strain PP RR M R = DD RR

21. Resilient Modulus Test Axial Compression  Used primarily for testing of bound materials (prepared specimens or core samples) OEM, Inc. © 2000 LoadRam LoadCell LVDT Gage Length  Heavier duty test equipment is used to measure compressive strength to measure compressive strength

22. Complex Modulus (E*)  a.k.a.: dynamic modulus  Applicable to bituminous materials  Equipment and test procedure almost identical to resilient modulus under axial compression  Primary difference is in load pulse (haversine vs. sinusoidal)  AASHTO 2002 Guide for Design of New and Rehabilitated Pavement Structures

23. Hveem Resistance Test (R-value)  Stiffness measure for unbound materials  Standard axial stress (  v ) is applied  R-value is basically the ratio of the applied vertical pressure (  v ) to the developed lateral pressure (  h ) vvvv hhhh 150mm 100 mm

24. California Bearing Ratio (CBR) Test  Strength measure for unbound materials  Piston advanced at 1.3 mm / min. rate  Measure load at 2.5 mm penetration (P 2.5 )  CBR = 100  (P 2.5 /P std ) SaturatedSpecimen 50 mm diameter piston 150 mm 180 mm

25. Indirect Tension Test  a.k.a.: Splitting tension or split tensile test  Used to determine the tensile strength and/or Mr of any bound material  100 or 150 mm diameter (D) specimens  Sample length should be at least half the diameter  Prepared samples or cores

26. Evaluating Pavement Layers Subgrade Soils  Soil classification (Unified or AASHTO)  Moisture content and density  DCP  Resilient modulus:  Measure in the lab  Backcalculate from NDT data  Estimated from correlation with R- value, CBR, or other soil properties

27. Evaluating Pavement Layers Unbound Base & Subbase Layers  Visual inspection  Layer thickness  Degradation or contamination by fines  DCP  Density and moisture content  Resilient modulus

28. Evaluating Pavement Layers HMA Surface and Stabilized Base Layers  Visual inspection of cores  Layer thickness  Stripping, segregation, erosion  Asphalt content and gradation  Resilient modulus  Lab measured (indirect tension)  Backcalculated

29. Other Considerations  Volume stability  Stripping  Seasonal variations in moisture  Permeability

30. Use of Field and Lab Tests in Rehabilitation Design  Help characterize existing support and quantify effect of deterioration  Field and lab testing vary depending on:  Material type (i.e., subgrade soil, unbound base or subbase, and HMA surface or stabilized base)  Candidate types of rehabilitation treatments (for example, recycling justifies a higher level of lab testing)

31.  What are two situations where field sampling and lab testing may be required?  What kind of sampling and testing would you now consider?  What is the motivation for resilient modulus testing?  Name two ways in which field/lab test results can be used in rehab design? Review

32. Key References  Washington State Department of Transportation (WSDOT). 1995. WSDOT Pavement Design Guide. Washington State Department of Transportation, Olympia, WA.  Livneh, M. 1987. “The Use of Dynamic Cone Penetrometer in Determining the Strength of Existing Pavements and Subgrades.” Proceedings, 9 th Southeast Asian Geotechnical Conference. Bangkok, Thailand.