GeoGauge 

1. GeoGauge Compaction Evaluation Today Stiffness-Based QC/QA

2. Humboldt Mfg. Co.Norridge, Illinois U.S.A. Mr. Scott Fiedler Product Manager Manufacturer & Distributor since 1909 Testing Equipment For Road Building Materials: Asphalt Concrete Soil Laboratory Apparatus

3. In-placestiffness & modulus Young’s Modulus Elastic Modulus Resilient Modulus resistance to change in shape in direction of stress Layer Stiffness resistance to deflection

4. Why Stiffness Based Compaction?(Why Measure Stiffness?) • Objective To Improve Load Bearing Capability • Reduce Variability • Enable Effective Load Transfer & Distribution, Pavement To Subgrade • Material Moduli • New Benefits • Minimized Pavement (Surface) Damage • Double Surface Life • Stiffness Makes Engineering Sense

5. Improvements With Stiffness Measurements • Optimum Compaction Effort • Reduce Over-Compaction • Reduce Variations • Reduce Maintenance & Repair Costs • Longer Lasting Smooth Surface • Verify Supporting Base Properties • Increase Surface Performance and Life

6. Benefits Of Stiffness Based QC Compaction • Minimized Pavement Surface Damage • > 50% Increase In Roadway Life • > 50% Decrease In Roadway Maintenance Cost • Directly Links Construction With Design • Design & Construction Parameters Are The Same • Enables Performance Specifications And Contractor Warranties • Enables Use Of Reasonable Design Margins • No Over Specification • No Over Construction

7. Variability • Control Of Compaction Process Enable Control Of Variability • Increase Life & Load Capacity.

8. Stiffness Variability Is Important “ By reducing the variability of layer stiffness to +/- 25% of the mean, the life of the pavement surface will double over current practice.” (FHWA) Easily Achieved !

9. What GeoGauge Measures • In-Place (In-Situ), 230 to 310mm Layer From Surface • During The Compaction Process For Effective QC/QA • Effective Young’s Modulus(elastic,resilient) • Influenced By Normal Construction Boundaries • Influenced By Construction/Contractor Operation • Modulus Of A Layered Composite Material • Modulus Of A Composite Material • Lower Than The Sum Of The Moduli Of The Constituent Materials • Effective Stiffness Of Composite Or Layered Structure • Influenced By Material Modulus, Layer Dimensions And Layer Boundaries • 230 to 310 mm from surface

10. GeoGauge Vibrates Ground & Measures the Deflection Superior Steady-State Sinusoidal Loading Technology 7,400 cycles !

11. Basic GeoGauge Specifications • 280 x 270 mm, 10 kg • Effective Young’s Modulus: 610 MPa • Effective Layer Stiffness: 70 MN/m • Depth: 230 to 310 mm From Surface • Battery Power • Measurement Duration: 75 Seconds • No License Required

12. GeoGauge Schematic

13. GeoGauge Features • Does Not Interfere Or Delay Construction • Detects Small Differences • Self-Contained & Hand-Portable • Quick • Not Affected By Construction Vibration, Wind or Slope • Robust, Reliable, Low Cost & Easy To Use • Established Bias, < 1% COV • Established Precision, Typically < 7% COV • Meets ASTM D6758

14. GeoGauge Procedure Is Simple Inspect GeoGauge & Power On Select Mode & Poisson’s Ratio Prepare & Smooth Ground Seat Foot Place & 1/2 turn on soft materials Place & 1/4 turn with wet sand over hard materials or rough surfaces Take Measurement: 75 sec. Record Data

15. Simple, Quick & Safe ! Remove Lose Material Smooth Surface Moist Sand Fill Voids Pat Firmly Sand Pad Place GeoGauge Press Measure Button Result In 75 Seconds

16. Seating On Hard or Rough Surfaces Use Wet Sand To Ensure Maximum Contact

17. GeoGauge Applications • Compaction QC/QA • Unbound & Bound Materials • Soil, Soil-Aggregates & Aggregates • Cement Treated Materials • Minimize Asphalt Surface Reflective Cracks • Subgrade & Base Stabilization • Ensure Required Strength & Minimize Construction Down Time • Trench / Utility Cut Backfill • Ensure Duplication Of Original Properties • Hot & Cold Mix Asphalt QC/QA • Compaction & Strength Evaluation • Forensic Investigations

18. Stiffness-Based Specifications • FHWA / 25 State DOTs Development Of AASHTO Standard • Specifications Underway For 2006 Construction Season

19. Specified For QC/QA of Roadway Layers & Cement-Treated Bases

20. Specified To Implement Mechanistic-Empirical Design Measure Material’s In-Place Modulus Level 1 Input (AASHTO 2002 Guidelines)

21. QC/QA of Granular Materials Measurements Yield Dry Density

22. Density Relationship

23. Density Relationship

24. Possible QC/QA Criteria! 400 Field Tests Lab Tests 300 Log(E-Ge) = 0.54 * log(E-PLT) + 2.22 2 R = 0.725 GeoGauge (MPa) 200 100 0 0 100 200 300 400 500 Plate Load Test (MPa)

25. Geogauge - FWD FWD = 1.355 Geogauge – 39.8 R2 = 0.81 at 95% level confidence N=29 FWD (MPa) GeoGauge (MPa)

26. Subgrade & Base Materials In 6 TXDOT Districts Seismic, E Section 17, Mn/ROAD S (MPa) Seismic vs. GeoGauge Modulus 2500 Modulus Compaction E = 6.27E - 31.91 (MPa) (%) 2000 S G Correlation Coefficient: .79 200 120 1500 1000 150 115 PFWD (small plate) PFWD (large plate) 500 100 110 DCP (6" avg.) 0 0 50 100 150 200 250 300 350 400 DCP (3" avg.) GeoGauge, E , (MPa) G 50 105 GeoGauge FWD, E F sc compaction (MPa) FWD vs. GeoGauge Modulus 0 100 ng compaction 1500 E = 4.08E - 231.53 1200 F G Correlation Coefficient: .80 -50 95 900 1 2 3 4 5 6 600 300 13 Pavement Sections at 5 MnDOT Sites 0 0 50 100 150 200 250 300 350 400 GeoGauge, E , (MPa) G Correlation to Other Moduli

27. GeoGauge Operation Principle • Cyclic Vertical Loading 7400 X • 25 Discrete Frequencies • 100 To 196 Hz, 4 Hz Increment, 2 Seconds Each • Each Frequency = 1 Test, Result is Average of 25 • Self-Filtering • Ground Anomaly / Infinitely Variable • 2 Geophone Sensors & 1 Driver • 1 Force • 1 Displacement

28. Operation Principles cont. • Stiffness = Force over Displacement. • At Low Frequencies, ground-input impedance is dominantly stiffness controlled.

29. Operation Principles cont. • Internal Flexible Plate is Reference Stiffness.

30. Operation Principlescont. • Relationship Of Stiffness To Young’s & Shear Modulus . (Poulos & Davis)

31. Operation Principles cont. Averaging Over Operating Frequencies & Substituting Velocity, V, for Displacement, X, Ground Stiffness Is As Follows. Avoids the need for non-moving reference for displacement & permits accurate measurement of small displacements

32. Calibration Principles

33. Review • Stiffness Based Compaction QC/QA Makes Sense • Minimized Pavement Damage • Directly Links Construction With Design • Enables Use Of Reasonable Design Margins • GeoGauge Measures Stiffness • In-Place Layer Stiffness & Modulus Of Composite Materials • GeoGauge Is Practical For QC/QA • Small, Light, Quick, Simple & Non-Invasive • Many Applications • Roadway & General Compaction • Subgrade, Base & Pavement • Soil, Aggregate & Asphalt

34. Verifier Mass Ensures Operation • Measures ‘stiffness’ value of compliant-mounted mass. (10.0 kg) • Average of 3 to 5 measurements, remove & rotate 45 to 90 degrees between measurements. Should be -9.3 +/- 5%. (Between -8.8 & -9.8) • Negative sign represents mass.

35. Verify Operation Daily • To be made at the beginning of every test day. • Ensures operation is correct. • Deviations can be easily corrected by calibration on same Verifier Mass.

36. GeoGauge™Use & Seating Procedure Seating & Measurement Procedures For Proper GeoGauge Measurements

37. GeoGauge Seating Procedure • Established Jointly with State DOTs, FHWA & Humboldt • Procedure Standardized • ASTM D6758 • Operator Bias Minimized or Eliminated

38. Firmly Hand-Pack Wet Sand • One small handful • Fills cavities • Hand-packing does not change material properties • Make Sand Pad approximately 150mm dia. x 3 to 6mm thick • Placing and quarter-twist of GeoGauge further reduces amount of sand between ring foot and material surface

39. Practice, Practice, Practice • A must for new technicians or users • Becomes proficient & confident • Ensures reliable measurements on projects • Practice on ‘real’ compacted surfaces • Recommended for experienced users • Profiles & Identifies Deviations Faster • Quickly addresses problems while equipment still on-site • Primary QC benefit

40. Confirm Measurement Precision • Minimum of three (3) measurements on representative site and material. • At the beginning of each test day and each site. • Confirm precision. • About 8% COV or less is good. • Practice & experience improves COV.

41. Suggested Supplies • Brush to remove loose materials • Gloves & knee-pads • Helps to prepare surfaces more quickly • All supplied by technician or user. • Not shown: paper & pen to document measurement data, material type & water content, layer thickness and other conditions for database purposes.

42. Prepare Surface • Use a solid scraper to remove any loose, dry, hard top materials and to make surface flat. • Use brush to help remove readily loose materials. • Surface must be moist and free of loose materials before wet sand is applied. • Any user supplied flat scraper or stiff brush can be used.

43. Brush Away Loose Material • Can be used instead of scraper plate. • Use brush to quickly remove loose material. • Do not ‘pick’ or remove protruding attached stones or disturb material.

44. Container of Wet Sand • Use fine, well-graded & clean manufactured sand that has good adhesion when wet. • Often called masonry or mortar sand. • 10 to 15% moisture is ideal.

45. Place Wet Sand • A small handful is generally all that is required for freshly compacted material. • Drop onto the surface. • Sand may not be required if ring-foot pattern is clearly visible without sand, which indicates soil is soft enough to conform to ring-foot for complete contact.

46. Small Handful of Wet Sand

47. Firmly Hand-Pack Wet Sand • Spread the sand to a pad shape about 150mm dia. & no more than 6mm thick. • Use more sand for a thicker pad when required where surface is rough. • Pack firmly, equal & smooth.

48. Always Use Wet Sand • Ensures Full & Equal Annular Contact • Repeatability • Thin layer of sand has no influence • Well-Graded, Fine Mortar or Masonry Sand • Provides good adhesion • 10 to 20% moisture • Sand may not be required if, without sand, a complete 360 degree ring-foot pattern is clearly visible, which indicates soil is soft enough to conform to ring-foot for complete contact.

49. Place GeoGauge • Rest GeoGauge ring-foot on center of sand pad. • No addition downward force.

50. Twist One/Quarter Turn • With both hands on side of GeoGauge, apply a one-quarter turn or twist only, to complete the seating. • Do not apply additional downward force. • Most critical step in seating the GeoGauge.