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NDOR Research Conference: Dr. Cho


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Nebraska Department of Roads Conference 2012
Presented by Dr. Yong K. Cho

Published in: Automotive, Technology, Business
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NDOR Research Conference: Dr. Cho

  1. 1. Non-nuclear Methods for HMA and Soil Density Yong K. Cho, Ph.D. Associate ProfessorDurham School of Architectural Engineering and Construction
  2. 2. Outlines• Hot Mix Asphalt (HMA) Testing – Objective – Data Analysis – Error Modeling – Conclusion and Recommendations• Soil Testing – Objective – Literature on Gauges – Data Analysis – Conclusion ad Recommendations• Economic Analysis
  3. 3. HMA Testing: Objective• Main research objective is to study effectiveness of non-nuclear gauge (PQI 301) with the nuclear gauge (Troxler) and develop methods to improve non-nuclear gauge’s performance for Quality Control and Quality Assurance – 13 sites were investigated for two years – Data size: 150 cores + more for calibration – SP4 and SPR used for the top layer of pavements
  4. 4. Gauge Test Results• The densities of two gauges were compared to corresponding core densities• Average density error with cores: – Pavement Quality Indicator: 1.89 lb/cu.ft – Nuclear: 1.07 lb/cu.ft• Site average ( 2) – Pavement Quality Indicator: (r =0.63, 2 =0.4) – Nuclear: (r=0.88, 2=0.78 )
  5. 5. Data Reliability (Core sample vs.Maximum Theoretical Density)• Core samples compared to the MTD (%) – Distribution of when exactly it is appropriate to reasonable accept gauge readings This is important information when cores are selected to calibrate PQI at first place
  6. 6. Data Reliability (Both Gauges vs.Maximum Theoretical Density)• PQI and Nuclear densities compare to the MTD (%)
  7. 7. Error Modeling to Improve PQIAccuracy Using Core Samples inCalibration Process
  8. 8. Summary of PQIImprovement Process
  9. 9. Soil Testing: Objective• Research objective is to investigate the effectiveness of: Troxler’s Nuclear Gauge, Humboldt’s Electrical Density Gauge, Durham Geo’s Moisture and Density Indicator and Zorn’s Light Weight Deflectometer vs. Traditional Methods• Research team followed: – Nuclear Method (ASTM D2922, AASHTO T-310, for Field and Lab Tests – Known soil curves provided by NDOR – The Standard Test Method for density of soil in place by the Drive-Cylinder Method (ASTM D2937-10) – Shelby Tube – Standard Proctor Compaction Test – Water content determination by Dry-Oven Method
  10. 10. Electrical Density Gauge(EDG)• Provides density, % compaction, moisture content• Needs a soil model to “calibrate” device• Requires use of mold
  11. 11. Light Weight Deflectometer(LWD)• Measures stiffness of the soil• Used by the Minnesota Department of Transportation for QA
  12. 12. Two Sites• Highway 370 by Gretna, NE• Platteview intersection site near Plattsmouth, NE• Total of 118 spots were measured
  13. 13. Test Results
  14. 14. LWD Test Analysis• Issue in comparison: Deflection vs. Density• A test is deemed passed or failed when the measured density is within 95% of the maximum density along with moisture requirements• Passes or fails for LWD using target value methodology adopted by MnDOT
  15. 15. Test Status Analysis
  16. 16. Economic Analysis • Nuclear Gauge Costs
  17. 17. Economic Analysis
  18. 18. Economic Analysis (BreakEven Point)
  19. 19. New Non-nuclear Technologies
  20. 20. Framework for EvaluatingHMA Gauges
  21. 21. Framework for EvaluatingSoil Gauges
  22. 22. Conclusions• Overall, the nuclear gauge shows higher accuracy and correlation than non-nuclear Hot Mix Asphalt and soil gauges• Methodologies to improve PQI’s performance were developed and presented• When cores and PQI had a higher density (%), statically PQI had higher accuracy than the nuclear gauge• The trend line error modeling method showed the accuracy improvement when more cores were used for calibration• LWD shows promising test results• Great cost savings can be expected when non-nuclear method is adopted
  23. 23. CREDITS Yong K. Cho, Ph.D. Associate ProfessorDurham School of Architectural Engineering and Construction Slide design © 2009, Mid-America Transportation Center. All rights reserved.