Nuclear vs. Non-nuclear Testing and Transition – Development of curves

1. Nuclear vs. Non-nuclear Testing and Transition – Development of curves Mark Lindemann NDOR Geotechnical Engineer

2. Outline • Background on previous field testing • Research – Non-nuclear field testing • Cost Savings of Going Non-Nuclear • Fundamentals of LWD • LWD Correlation • Field Implementation

3. Density and Moisture Testing • Volumemeasure Test Method

4. Density and Moisture Testing • Nuclear Density & Moisture Gauge (NDG)

5. NON-NUCLEAR DENSITY TESTING • Why fix what isn’t broken? • Nuclear Gauges – • Regulations • Licensing • Storage and transport • Training • Costs add up • Have 84 gauges needing replacement • Possible Fines • Approximately $250,000/ year Falls in Line with Every Day Counts Initiative Innovative Technologies

6. Non-Nuclear Research • University of Nebraska – Dr. Yong K. Cho • Non-Nuclear Methods for HMA and Soil Density • Historical research • Field Research: PQI (HMA) • Compare to Nuclear Density Gauge • Bulk Specific Gravity of Asphalt Cores (AASHTO T166)

7. Asphalt Non-Nuclear • PQI (Pavement Quality Indicator) • Measures the change in electromagnetic field as current is sent through the material. • Calibrated with average of 5 core densities and average of 5 PQI densities.

8. Asphalt Non-Nuclear • Results: • Both Nuclear and PQI provided results very close to asphalt core values • Nuclear gauge closer to asphalt core values (+1.07 lb/ft3) • PQI gauge values -1.89 lb/ft3 to asphalt core values.

9. Asphalt Non-Nuclear

10. Asphalt Non-Nuclear

11. Non-Nuclear Research

12. Non-Nuclear Research - Soils • Field Research: EDG, M+DI, LWD • Compared to Nuclear Moisture Density Gauge • Density of Soil from Shelby Tubes (ASTM D2937) • Water Content via Oven Dry Method

13. Soils Non-Nuclear • Electrical Density Gauge (EDG) • Uses high radio frequency waves to electrical dielectric properties of soil. • Requires complex correlation of expected field density & moisture values ahead of time. • Need to perform some other test method for density and moisture in the field first. • Results: Density, % Moisture, % Compaction • For each soil type – Need a Soil Model

15. Soils Non-Nuclear Nuclear Results: • Average difference of 1.71 pcf compared to standard for density. • Average difference of 0.22% for moisture. EDG Results: • Average difference of 9.86 pcf compared to standard for density • Average difference of 1.66% for moisture.

16. Soils Non-Nuclear • M+DI (Moisture Density Indicator) • Uses Time Domain Reflectometry to send electromagnetic pulse through soil • Requires correlation of several points from Proctor tests • Takes 15 to 20 minutes per test. • Had trouble with device at beginning • Removed from testing

21. Soils Non-Nuclear • Light-Weight Deflectometer (LWD) • Measures soil surface deflection • Provides Modulus, Deflection, Velocity • No moisture content results

22. Soils Non-Nuclear LWD Results: • Compared Pass/Fail results based on 95% compaction of devices to standard (lab) • Nuclear Gauge: 72% correlation • LWD: 54% correlation • Overall – best correlation of new devices • Suggest better way to determine target value (not density)

23. Benefits/Limits of Density Testing • Widely Accepted QA/QC Method • Indirect Parameter of Strength • Small Variations – Result Large Variation in Stiffness • Compaction Lab vs. Compaction Field • Costs/Regulations of Nuclear • Results are Material dependent based on a small sample compared to that in the field.

24. Benefits/Limits of Stiffness Testing • Non-Nuclear • Good Correlation to FWD Technology • Poor Correlation to Lab Modulus Results • Variations between LWD Models • Not Really “Lightweight” • Results are Material and Device dependent • Need to use the same device for all testing • Greater Precision • Promotes Uniformity • Goal is uniform moisture and stiffness • Agreement between construction QA and pavement design. • Soil Stiffness – direct measurement that can be used to determine structural capacity of a soil (rutting). Longer pavement life. • No moisture testing capability.

25. Cost / Savings • LWD Initial Costs: $8,257 • Thermal Paper: $20/ Year • Maintenance/ Calibration: $300

26. Cost / Savings • Net Present Worth of Costs (NPW)= Initial Costs + Yearly Costs (P/A, 15 yrs, 10%) • NPW of Nuclear Gauge= $10,873 + $2,155(P/A, 15yrs, 10%) = $27,264 • NPW of LWD = $8,257 + $320(P/A, 15yrs, 10%) = $10,690

27. LWD Technology • Dynamic non-destructive testing tool • Measure layer/surface modulus (stiffness) • How it works • Transient Load on Loading Plate • Accelerometer within the device measures the deflection of the ground due to the load • Soil Modulus back-calculated based on deflection and assumed Poisson’s ratio. • Results taken as an immediate indication of the materials strength (ability to support roadway) http://www.youtube.com/watch?v=6WGgosXlHss

28. Modulus Calculation: Eo = f x (1-u2) xsox a / do Eo = Modulus f = Plate Rigidity factor (2) u = Poisson’s Ratio (0.35) so= Maximum contact stress a = Plate Radius do= Maximum deflection

29. LWD Models • Zorn • Keros • Dynatest • Prima • Loadman • ELE

30. LWD Test Method • ASTM E 2835-11 for LWD without Load Cell • ASTM E2583-07 for LWD with Load Cell • Plate Size • Drop Height • Falling Weight • Type and location of Sensors • Significant variability between manufacturers • Seating Load (3 Drops) • Testing Load (3 Additional Drops)

31. Other LWD Research • MnDot Research – Beginning 1997 • NCHRP – 382 & 456 • Colorado DOT • Vermont DOT • US Army Corps of Engineers • UK – Fleming, Frost, and Lambert • Virginia Transportation Research Council • Kansas DOT • Louisiana Transportation Research Center

32. Zorn LWD • Several LWD models with variety of differences • Steel spring buffer and accelerometer in plate • Critical to use same device with same plate diameter, drop height, and falling mass • Hand-held recording instrument • SD card memory • Graphical and numerical results • Printout of results • GPS capability

33. Typical Deflection Plot

34. Deflection Results Normal Result For unbound materials

35. Deflection Results Rebound Common for Bound materials If rebound is >20% Of Peak Re-seat and retest

36. Deflection Results Variable May be poor Compaction

37. Deflection Results

38. Testing • Recipe for Good Compaction • Know Soil Type • Moisture Control • Limit Lift Thickness • Compaction Testing • Stiffness/ Strength of materials • Target = Minimum Modulus or Maximum Deflection • Based on Material Type • Moisture Content • May Require A Test Strip

39. Field Testing • Side by Side LWD Tests & Nuke Tests • Bag Samples for Lab • Determine NGI & Moisture • Compare Deflection vs % Compaction for each Soil Type (NGI)

40. PI= 20 LL = 45 % Ret.= 50 Chart 2 = 3.5 NGI = 7 Chart 1 = 3.5

41. Ave. Velocity vs % Compaction

42. Dynamic Modulus vs % Compaction

43. Ave. Deflection vs % Compaction

44. Modulus Requirement • Modulus in Laboratory is complicated, expensive, and time consuming. • Test methods have continually changed over the years • NDOR – Resilient Modulus Research based on Nebraska Soil Types (NGI) • Correlate well with FWD • Do not correlate with LWD

45. Resilient Modulus Correlation to NGI

46. Deflection Requirement • Deflection is easy to understand • Two Specifications • 1. Provide Target Value for each NGI • 2. Perform Test Strip / Calibration Area

47. Field Specification 1 • Maximum Deflection based on Nebraska Group Index (PI, LL, #200) • First – Make sure moisture is within Spec. • Refer to Chart for Deflection Requirements

48. Goal: Maximum Deflection for Each NGI Soil Type Target Value = Max Deflection 1.2 mm For Equivalent to 95% Compaction 1.2

49. NGI = 7 Under Concrete Top 3’ NGI = 7 Under Asphalt Below 3’

50. Field Specification 2 • Deflection Data for Soil Type not available • Perform a Test Strip/ Calibration Area • First Test Moisture • Size of Test Strip – 200’ Length x Width of Embankment, Two-8” Lifts • 3 LWD Tests/ Roller Pass – Random Locations