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Dynamic 4D imaging of foamed bitumen by X-ray micro ... · Dynamic 4D imaging of foamed bitumen by X-ray micro computed tomography Iwan JERJEN1,2, Biruk HAILESILASSIE3, Philipp SCHUETZ5,

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  • Dynamic 4D imaging of foamed bitumen by X-ray micro computed tomography Iwan JERJEN1,2, Biruk HAILESILASSIE3, Philipp SCHUETZ5, Mathieu PLAMONDON4, Alexander FLISCH4, Manfred PARTL3

    1) Institute for Biomedical Engineering, ETHZ, Gloriastrasse 35, CH-8092 Zurich, Switzerland

    2) Laboratory for Macromolecules and Bioimaging, Paul Scherrer Institut, CH-5232 Villigen-PSI, Switzerland

    3) Road Engineering/Sealing Components, Empa, Ueberlandstrasse 129, CH-8600 Duebendorf, Switzerland

    4) Center for X-ray Analytics, Empa, Ueberlandstrasse 129, CH-8600 Duebendorf, Switzerland

    5) Lucerne University of Applied Sciences and Arts, Technikumstrasse 21, CH-6048 Horw, Switzerland


    Experimental setup


    Foamed bitumen allows mixing and compacting warm asphalt at lower

    temperatures, therefore reducing energy consumption and costs [1]. By

    mixing a small quantity of water, typically 1- 6.0 w-%, with hot bitumen,

    a foam is formed, which has, at a given temperature, better wetting and

    coating capabilities than bitumen alone [1]. The amount of water, the

    bitumen temperature and additives influence the structure and dynamics

    of foamed bitumen, which determines its properties, like expansion ratio

    and half-life time [2, 3].

    Fast X-ray computed tomography (4 s per 3D CT) allows investigating

    the time-resolved morphology of foamed bitumen if a stabilizer* is added

    to slow down the collapse of the foam. * TEGO Addibit FS 725 A, EVONIK, Switzerland







    1) X-ray flat panel detector (Perkin Elmer, XRD 1621 CN3 ES)

    2) Rotation table (Micos, UPR-160 F air) 3) XYZ stages (Micos, LS-270)

    4) X-ray microfocus tube (XT9160-TXD) 5) Bitumen supply hose

    6) Plexiglas cylinder with bitumen foam (Ø 104 mm)

    Image analysis


    Reconstruction method

    By means of a fibre reinforced plastic hose, 180° hot foamed bitumen was

    injected into a Plexiglas cylinder mounted on the rotation table of the X-

    ray system. The microfocus X-ray source was operated at 80 kV

    acceleration voltage and 300 µA (i.e. 24 W). The X-ray detector was read

    out with ~14.5 frames/s. The rotation speed was between 90 °/s.

    No filter Mean filter

    (radius 3), final choice

    Median filter Non-local means

    filter [5] Gauss filter

    Mean filter

    (radius 5)

    The three-dimensional shape of the foamed bitumen was calculated from

    59 projection images acquired over 360° by a Feldkamp algorithm [3].

    Because of the low SNR of the projection images, different filters were

    applied on the projection images prior to the reconstruction:

    [1] J. W. Button, C. Estakhri, and A. Wimsatt, System 7, 94 (2007).

    [2] M. F. Saleh, Int. J. Pavement Eng. 8, 99 (2007).

    [3] B. W. Hailesilassie, P. Schuetz, I. Jerjen, M. Hugener, and M. N. Partl,

    J. Mater. Sci. 50, 79 (2014).

    [4] L. A. Feldkamp, L. C. Davis, and J. W. Kress, J. Opt. Soc. Am. A 1, 612 (1984).






    Even a low power (24 W) microfocus X-ray tube allows obtaining

    reasonable fast (4s) 3D CT measurements for visualizing the time-

    evolution of foamed bitumen:

    • The use of a high power X-ray source would improve the SNR and

    spatial resolution considerably.

    • A faster X-ray detector would help to reduce motion artefacts.

    • Optimized noise filters may improve the results.

    • A gantry CT scanner would eliminate the centrifugal force artefacts.

    The 3D CT data was inverted and filtered with a Gaussian blur filter

    (radius 4) using the freeware Fiji [6], then the bubbles were segmented

    and the surface data saved in STL file format [7] using a trial version of

    VGStudio MAX [8]. The final visualization was done with the GOM

    Inspect freeware [9].


    t = 0 s

    Result not reliable due to

    motion artefacts!

    Nevertheless, bubbles

    are fairly flat and have a

    preferential direction,

    probably due to the

    initial spraying.

    t = 14 s

    Bubbles as small as

    ~0.5 mm3 can be seen.

    The bitumen cooled

    down a bit and is

    therefore less viscous:

    The shape of the

    bubbles becomes


    t = 34 s

    The bitumen collapsed

    considerably and the

    surface approaches the

    ROI. The CT data

    indicates that the

    bitumen is less dense

    close to the surface.