Nondestructive active surface wave testing of soils and pavements: modeling, testing, and inversion

Quality Control/Quality Assurance of Asphalt Mixtures Using Surface Wave MethodsShibin Lin, PhD Student

Jeramy Ashlock, Major Professor (PI)Christopher Williams (CoPI)Hosin (David) Lee (CoPI)

2013 Mid-Continent Transportation Research SymposiumDepartment of Civil, Construction, and Environmental EngineeringIOWA STATE UNIVERSITY#Significance of the Proposed StudyQualityDensity

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(Hanna, et al. 2008 )2/29the modulus or stiffness of the asphalt layer long-term durability and performance of asphalt pavements

#Significance of the Proposed StudyQualityStiffness or Moduluse.g. Arellano et al., 2003, from Texas DOTWilliams, et al., 2007, from ISU.Von Quintus et al., 2009, from ARA, INC.Structural propertyPerformance

Stress(Force)Strain (Displacement)Modulus (Stiffness)G=Vs2Shear modulus:3/29#OutlineEquipmentPaveTracker (dielectric constant Density)GeoGauge (mechanical impedance, force over deflection Stiffness)Custom-built surface wave testing equipment (wave speed G=Vs2)TestingBoone Central Iowa Expo project(36 base cores, 16 surface cores)ResultsDensityWave speedStiffnessCorrelationsPreliminary conclusionsFuture works4/29#GeoGauge(Humboldt)Equipment

PaveTracker(Troxler)Custom-built surface wave testing equipment (Lin&Ashlock)

5/29#Surface wave methodSurface 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.

FEM simulation of a transient impactDispersive nature of Rayleigh wavesPhase VelocityFrequency

Dispersion curve Layer thickness and stiffness6/29#

Surface wave methodBy measuring the experimental phase velocity versus frequency relation (termed the experimental dispersion curve or dispersion image), the material properties can be calculated in the form of layer thickness and moduli.7/29#Surface wave methodData acquisition and analysis system programmed in MATLAB

8/29#Surface wave method

joint between two lanesmiddle of one lane (2012, in HWY 61 Fort Madison)

The joint has lower wave speed and thus lower quality than the centerline .9/29#Testing

AsphaltBoone Central Iowa Expo project Base36 coresSurface16 cores10/29#Results: PaveTracker Density

36 base cores (4) from Boone

/7.410-42.510-33.710-43.410-4Hot = 1 to 3 hours after paving, Cold = next day (same locations)Increase in scatter and slight decrease in avg. density overnight11/29#

Results: SWM Wave speedSWM testing of Core 1-1

HOTCOLDRayleigh waves are faster in cold asphalt pavements than in hot ones12/29#Results: SWM Wave speed

36 base cores (4) from BooneThe dispersion images of cold asphalt pavements have wider frequency and velocity ranges than those of hot onesPick Rayleigh wave velocities at 230 Hz of hot dispersion images and at 2500 Hz of cold dispersion images for further studyHOTCOLD13/29#Results: SWM Wave speed

/ 7.2 10.0Velocity much more sensitive than density for assessing thermal effectsDue to large change of modulus w/temperature, Cold velocities should correspond to modulus from lab tests36 base cores (4) from Boone14/29#Results: Correlation between Lab Density Methods36 base cores (4) from BooneSSD density is highly correlated to CoreLok density15/29#Results: PT Density vs. Lab DensityHOTCOLD36 base cores (4) from BooneHigh correlation between hot PT density and Lab densityLow correlation between cold PT density and Lab density16/29#Results: SWM Velocity vs. Field/Lab DensityHOTCOLDVs = (G/)1/2COLDVery small correlation between PT density and wave speedLow correlation between PT density and wave speed17/29#Vs2 = G/Results: SWM Velocity vs. Lab DensityCOLD18/29#Results: Air voids, Temperature differenceAs air voids increases, wave speeds decreaseAs temperature differences increase, wave speed differences increasesAs temperature differences increase, density differences first decrease and then increase.

19/29#Results: PaveTracker Density16 surface cores (2) from BooneHot = 4 to 7 hours after paving, Cold = next day (same locations)Increase in scatter and slight decrease in avg. density overnight

/1.710-49.510-41.610-420/29#Results: PT Density vs. Lab Density16 surface cores (2) from BooneHOTCOLDLow correlation between hot PT density and Lab densityVery small correlation between cold PT density and Lab density21/29#

Results: SWM Wave speed16 surface cores (2) from Boone/1.96.7

Velocity much more sensitive than density for assessing thermal effectsDue to large change of modulus w/temperature, Cold velocities should correspond to modulus from lab tests22/29#Results: SWM Velocity vs. Field/Lab Density16 surface cores (2) from BooneHOTCOLDVery small correlation between Field/Lab density and wave speed23/29#Results: SWM Velocity vs. Lab Density16 surface cores (2) from BooneCOLD24/29#Results: GeoGauge stiffness16 surface cores (2) from Boone

/0.460.74Stiffness much more sensitive than density for assessing thermal effects25/29#Results: SWM Velocity vs. GeoGauge stiffness16 surface cores (2) from BooneHOTCOLDThe correlation between SWM velocity and GeoGauge stiffness of cold asphalt is higher than the correlation between SWM velocity and GeoGauge stiffness of hot asphalt.26/29#Results: Temperature difference16 surface cores (2) from BooneDensity difference has the lowest correlation to temperature differenceAs temperature differences increase, wave speed and stiffness differences increases

27/29#Preliminary conclusionsDensity slightly decreases overnight as pavement coolsStiffness and wave speed significantly increase overnight, due to setup causing increase in stiffness/modulusWave speed is not good indicator of density due to stronger dependence on modulus, which varies by orders of magnitudeWave speed can be a useful quantitative index for QA/QC based on pavement stiffness/modulus:Vs highly sensitive to modulus, temperatureClear differences found in pavement joints vs. centerline28/29#Future workTests 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.29/29#Thanks!Questions?#