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Quality Control/Quality Assurance of Asphalt Mixtures Using Surface Wave Methods

Quality Control/Quality Assurance of Asphalt Mixtures Using Surface Wave Methods. Shibin Lin, PhD Student Jeramy Ashlock , Major Professor (PI) Christopher Williams ( CoPI ) Hosin (David) Lee ( CoPI ) 2013 Mid-Continent Transportation Research Symposium.

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Quality Control/Quality Assurance of Asphalt Mixtures Using Surface Wave Methods

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  1. Quality Control/Quality Assurance of Asphalt Mixtures Using Surface Wave Methods Shibin Lin, PhD Student JeramyAshlock, Major Professor (PI) Christopher Williams (CoPI) Hosin (David) Lee (CoPI) 2013 Mid-Continent Transportation Research Symposium Department of Civil, Construction, and Environmental Engineering IOWA STATE UNIVERSITY

  2. Significance of the Proposed Study Density Quality (Hanna, et al. 2008 ) Density change overnight after paving: slight increase for seven projects, slight decrease for three projects. (Hanna, et al. 2008 from University of Wisconsin-Madison) Density

  3. Significance of the Proposed Study Shear modulus: G=ρVs2 Structural property Performance Modulus (Stiffness) Quality Stress (Force) e.g. Arellano et al., 2003, from Texas DOT Williams, et al., 2007, from ISU. Von Quintus et al., 2009, from ARA, INC. Stiffness or Modulus Strain (Displacement)

  4. Outline • Equipment • PaveTracker (dielectric constant  Density) • GeoGauge (mechanical impedance, force over deflection  Stiffness) • Custom-built surface wave testing equipment (wave speed  G=ρVs2) • Testing • Boone Central Iowa Expo project(36 base cores, 16 surface cores) • Results • Density • Wave speed • Stiffness • Correlations • Preliminary conclusions • Future works

  5. Equipment PaveTracker (Troxler) GeoGauge (Humboldt) • Custom-built surface wave testing equipment (Lin&Ashlock)

  6. Surface wave method Dispersive nature of Rayleigh waves FEM simulation of a transient impact Phase Velocity Frequency Layer thickness and stiffness Dispersion curve Surface wave methods make use of the dispersive nature of Rayleigh waves, which means that different frequency components of a wave travel at different phase velocities.

  7. Surface wave method By measuring the experimental phase velocity versus frequency relation (termed the experimental dispersion curve ordispersion image), the material properties can be calculated in the form of layer thickness and moduli.

  8. Surface wave method Data acquisition and analysis system programmed in MATLAB

  9. Surface wave method joint between two lanes middle of one lane • The joint has lower wave speed and thus lower quality than the centerline. (2012, in HWY 61 Fort Madison)

  10. Testing

  11. Results: PaveTracker Density 36 base cores (4”) from Boone • Hot = 1 to 3 hours after paving, Cold = next day (same locations) • Increase in scatter and slight decrease in avg. density overnight

  12. Results: SWM Wave speed SWM testing of Core 1-1 COLD HOT • Rayleigh waves are faster in cold asphalt pavements than in hot ones

  13. Results: SWM Wave speed 36 base cores (4”) from Boone COLD HOT • The dispersion images of cold asphalt pavements have wider frequency and velocity ranges than those of hot ones • Pick Rayleigh wave velocities at 230 Hz of “hot” dispersion images and at 2500 Hz of “cold” dispersion images for further study

  14. Results: SWM Wave speed 36 base cores (4”) from Boone • Velocity much more sensitive than density for assessing thermal effects • Due to large change of modulus w/temperature, “Cold” velocities should correspond to modulus from lab tests

  15. Results: Correlation between Lab Density Methods 36 base cores (4”) from Boone • SSD density is highly correlated to CoreLok density

  16. Results: PT Density vs. Lab Density 36 base cores (4”) from Boone HOT • High correlation between • “hot” PT density and Lab density COLD • Low correlation between “cold” PT density and Lab density

  17. Results: SWM Velocity vs. Field/Lab Density Vs = (G/ρ)1/2 COLD HOT • Very small correlation between PT density and wave speed COLD • Low correlation between PT density and wave speed

  18. Results: SWM Velocity vs. Lab Density Vs2 = G/ρ COLD

  19. Results: Air voids, Temperature difference • As air voids increases, wave speeds decrease • As temperature differences increase, wave speed differences increases • As temperature differences increase, density differences first decrease and then increase.

  20. Results: PaveTrackerDensity 16 surface cores (2”) from Boone • Hot = 4 to 7 hours after paving, Cold = next day (same locations) • Increase in scatter and slight decrease in avg. density overnight

  21. Results: PT Density vs. Lab Density HOT 16 surface cores (2”) from Boone • Low correlation between • “hot” PT density and Lab density COLD • Very small correlation between “cold” PT density and Lab density

  22. Results: SWM Wave speed 16 surface cores (2”) from Boone • Velocity much more sensitive than density for assessing thermal effects • Due to large change of modulus w/temperature, “Cold” velocities should correspond to modulus from lab tests

  23. Results: SWM Velocity vs. Field/Lab Density HOT 16 surface cores (2”) from Boone • Very small correlation between Field/Lab density and wave speed COLD

  24. Results: SWM Velocity vs. Lab Density 16 surface cores (2”) from Boone COLD

  25. Results: GeoGauge stiffness 16 surface cores (2”) from Boone • Stiffness much more sensitive than density for assessing thermal effects

  26. Results: SWM Velocity vs. GeoGauge stiffness 16 surface cores (2”) from Boone HOT COLD • The correlation between SWM velocity and GeoGauge stiffness of cold asphalt is higher than the correlation between SWM velocity and GeoGauge stiffness of hot asphalt.

  27. Results: Temperature difference 16 surface cores (2”) from Boone • Density difference has the lowest correlation to temperature difference • As temperature differences increase, wave speed and stiffness differences increases

  28. Preliminaryconclusions • Density slightly decreases overnight as pavement cools • Stiffness and wave speed significantly increase overnight, due to setup causing increase in stiffness/modulus • Wave speed is not good indicator of density due to stronger dependence on modulus, which varies by orders of magnitude • Wave speed can be a useful quantitative index for QA/QC based on pavement stiffness/modulus: • Vs highly sensitive to modulus, temperature • Clear differences found in pavement joints vs. centerline

  29. Futurework Tests on 24 more cores from four highways in Iowa. More data for verifying preliminary conclusions for different pavement types (CIR, FDR, overlay, modified binders). Modulus measurement in laboratory and correlation to field velocity (at same temperature). More sophisticated SWM testing equipment and software. Quantitative quality index based on wave speed.

  30. Thanks! Questions?

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