Determining Aggregate Determining Aggregate Characteristics of HMA: Characteristics of HMA:

3D Processing of X3D Processing of X--ray CT Images ray CT Images

M. Emin Kutay, Ph.D.M. Emin Kutay, Ph.D.Asphalt Mixture Scientist / Lab ManagerAsphalt Mixture Scientist / Lab ManagerTurnerTurner--Fairbank Highway Research CenterFairbank Highway Research Center

Muhammed.Kutay@fhwa.dot.govMuhammed.Kutay@fhwa.dot.gov

Acknowledgements:Acknowledgements:Nelson Gibson, Ph.D.Nelson Gibson, Ph.D.Jack Youtcheff, Ph.D.Jack Youtcheff, Ph.D.Rick Meininger, P.E.Rick Meininger, P.E.Edith Arambula, Ph.D.Edith Arambula, Ph.D.

Effect of aggregate propertiesEffect of aggregate properties

•• Fine Fine graded HMA mixgraded HMA mix–– CoarseCoarse AggrAggr: Little or no contact points: Little or no contact points–– FineFine AggrAggr: Very important: Very important

•• Coarse Coarse graded HMA mixgraded HMA mix–– CoarseCoarse AggrAggr: Some contact points: Some contact points–– FineFine AggrAggr: Important: Important

•• SMA SMA MixMix–– CoarseCoarse AggrAggr: Many contact points: Many contact points–– FineFine AggrAggr: Less important: Less important

Steps of ImageSteps of Image--based Aggregate Extractionbased Aggregate Extraction

Varying aggregate type, Varying aggregate type, compaction characteristicscompaction characteristics

Specimen Prep.Specimen Prep.(Lab compacted / (Lab compacted /

field core)field core)

Measurement of 3D Measurement of 3D internal geometryinternal geometry XX--ray CT imagingray CT imaging

Rigorous image Rigorous image processing & analysisprocessing & analysis

Separation of aggregatesSeparation of aggregates

Individual aggregate props:Individual aggregate props:3D orientation, angularity, 3D orientation, angularity, Specific surface area Specific surface area ……etc.etc.

Calculation of contact Calculation of contact pointspoints

XX--ray Computed Tomography setupray Computed Tomography setup

X-Ray Source

Detector

Specimen

AlgorithmsCT# (in)

CT# (Out)

Vertical shift

Direct measurement of Direct measurement of aggregateaggregatecharacteristics: characteristics: 3D image3D image analysisanalysis

X-ray CT

Characteristics of Characteristics of aggregatesaggregatespackedpacked in an in an asphaltasphalt mixturemixture

–– 3D 3D Contact pointsContact points (or (or influence zone)influence zone)

–– 3D 3D OrientationOrientation–– SegregationSegregation: :

••Spatial distribution of Spatial distribution of different sizesdifferent sizes

–– 3D 3D AngularityAngularity, , sphericitysphericity, , specific specific surface areasurface area and and texturetexture

Aggregate contact pointsAggregate contact points•• Given : Given : ggradation and compaction radation and compaction

levellevel–– Variation of Variation of contact pointscontact points for for

different aggregates: different aggregates: rectangularrectangular, , flat , elongated and roundflat , elongated and round

•• Locking pointLocking point

•• Effect of number of Effect of number of contact pointscontact pointson HMA on HMA performanceperformance

•• Mix design Mix design consideringconsidering contact contact points points andand packingpacking

Challenge in Challenge in experimentationexperimentation: : separation of aggregatesseparation of aggregates

IdealIdeal RealReal

ThresholdingThresholding and labeling and labeling (2D description)(2D description)

Intensity Distribution

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0 255

Grayscale imageGrayscale image ThresholdedThresholded binary imagebinary image

ThresholdingThresholding and labelingand labeling(2D description)(2D description)

Binary imageBinary image Labeled imageLabeled image

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Original Gaussian smoothed Hmax filtered

Watershed transformed imageInverted Watershed lines

Filtered watershed transformation

Original Gaussian smoothed Hmax filtered

Watershed transformed image

Watershed transformed image

Watershed transformed image

Not good Not good Good

ThresholdingThresholding and labelingand labeling

Intensity Distribution

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Image after watershedImage after watershed Labeled imageLabeled image

NoThresholdingThresholding &&labelinglabeling

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3D 3D HmaxHmaxfilteringfiltering

3D Gaussian 3D Gaussian smoothingsmoothing

Original 3D imageOriginal 3D image

3D Watershed 3D Watershed surfaces (lines)surfaces (lines)

Separation of aggregates:Separation of aggregates:3D image processing steps3D image processing steps

ThresholdingThresholding IsuesIsues……Different intensitiesDifferent intensities

Dynamic Dynamic thresholdingthresholding in 2Din 2D

0 100 200 3000

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peak

# of

pix

els

Grayscale intensity

Dynamic Dynamic thresholdingthresholding in 3Din 3D

0 100 200 3000

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Intensity histogram

peak

# of

pix

els

Grayscale intensity

Calculation of aggregate properties

– 3D Contact points – 3D Orientation– 3D Volume,

Angularity, Specific surface area

– Segregation: • Spatial distribution

of different sizes

Calculation of contact points

Shortest distance between surface

voxels

Example calculationsExample calculations

0 1 2 3 40

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ulat

ive

dist

ribut

ion

(%)

Specific Surface Area (1/mm)

AggregatesSphere equivalent

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Specific Surface Area (1/ mm)

Cum

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ive

dist

ribut

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AggregatesSphere Equivalent

N160

N35

N160

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Example calculationsExample calculations

0 10 20 300

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EquivDiameter

Cum

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ive

dist

ribut

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(%)

N35N160

N160

N35

XX--ray CT Image 3D Analysis Toolray CT Image 3D Analysis Tool

Thank You!Thank You!Try to catch the rotating snake with your eye!Try to catch the rotating snake with your eye!

The EndThe EndM. Emin Kutay, Ph.D.M. Emin Kutay, Ph.D.

Asphalt Mixture Scientist / Lab ManagerAsphalt Mixture Scientist / Lab ManagerTurnerTurner--Fairbank Highway Research CenterFairbank Highway Research Center

mkutay@fhwa.dot.govmkutay@fhwa.dot.gov