Wide-range optical pH imaging of cementitious materials exposed to chemically corrosive environments

Bernhard Müller, Cyrill Grengg, Viktor Schallert, Marlene Sakoparnig, Christoph Staudinger, Johanna Breininger, Florian Mittermayr, Birgit Ungerböck, Sergey Borisov, Martin Dietzel, Torsten Mayr

Publikation: Beitrag in einer FachzeitschriftArtikelForschungBegutachtung

Abstract

The pH of concrete‐based material is a key parameter for the assessment of its stability and durability, since a change in pH is usually associated with major types of chemical degradation such as carbonation, leaching and acid attacks. Conventional surface pH measurements with potentiometric flat surface electrodes have low spatial resolution, whereas optical pH visualization with indicator dyes (phenolphthalein) only indicates the areas with higher or lower pH than the pKa of the indicator. In this regard, it is key to develop wide‐range imaging systems, enabling accurate and spatially resolved determination of pH variability for an advanced knowledge of degradation mechanisms. This contribution presents the enhancements made for a high‐resolution optical pH imaging system based on fluorescent aza‐BODIPY indicator dyes. The measurement range was increased to 6 pH units (pH 6.5 to pH 12.5) by a combination of two indicator dyes. Moreover, background scattering effects were sufficiently eliminated. With the improved sensor foils steep pH gradients (up to 3 pH units within 2 mm) were successfully recorded in various concrete specimens using a macro lens reaching a resolution of down to 35 μm per pixel.
Originalspracheenglisch
Seiten (von - bis)39-45
FachzeitschriftRILEM Technical Letters
Jahrgang3
PublikationsstatusVeröffentlicht - 2 Nov 2018

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Caustics
Coloring Agents
Imaging techniques
Imaging systems
Phenolphthalein
Degradation
Carbonation
Metal foil
Leaching
Macros
Lenses
Durability
Visualization
Pixels
Concretes
Scattering
Electrodes
Acids
Sensors

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    Wide-range optical pH imaging of cementitious materials exposed to chemically corrosive environments. / Müller, Bernhard; Grengg, Cyrill; Schallert, Viktor; Sakoparnig, Marlene; Staudinger, Christoph; Breininger, Johanna; Mittermayr, Florian; Ungerböck, Birgit; Borisov, Sergey; Dietzel, Martin; Mayr, Torsten.

    in: RILEM Technical Letters, Jahrgang 3, 02.11.2018, S. 39-45.

    Publikation: Beitrag in einer FachzeitschriftArtikelForschungBegutachtung

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    title = "Wide-range optical pH imaging of cementitious materials exposed to chemically corrosive environments",
    abstract = "The pH of concrete‐based material is a key parameter for the assessment of its stability and durability, since a change in pH is usually associated with major types of chemical degradation such as carbonation, leaching and acid attacks. Conventional surface pH measurements with potentiometric flat surface electrodes have low spatial resolution, whereas optical pH visualization with indicator dyes (phenolphthalein) only indicates the areas with higher or lower pH than the pKa of the indicator. In this regard, it is key to develop wide‐range imaging systems, enabling accurate and spatially resolved determination of pH variability for an advanced knowledge of degradation mechanisms. This contribution presents the enhancements made for a high‐resolution optical pH imaging system based on fluorescent aza‐BODIPY indicator dyes. The measurement range was increased to 6 pH units (pH 6.5 to pH 12.5) by a combination of two indicator dyes. Moreover, background scattering effects were sufficiently eliminated. With the improved sensor foils steep pH gradients (up to 3 pH units within 2 mm) were successfully recorded in various concrete specimens using a macro lens reaching a resolution of down to 35 μm per pixel.",
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    T1 - Wide-range optical pH imaging of cementitious materials exposed to chemically corrosive environments

    AU - Müller, Bernhard

    AU - Grengg, Cyrill

    AU - Schallert, Viktor

    AU - Sakoparnig, Marlene

    AU - Staudinger, Christoph

    AU - Breininger, Johanna

    AU - Mittermayr, Florian

    AU - Ungerböck, Birgit

    AU - Borisov, Sergey

    AU - Dietzel, Martin

    AU - Mayr, Torsten

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    Y1 - 2018/11/2

    N2 - The pH of concrete‐based material is a key parameter for the assessment of its stability and durability, since a change in pH is usually associated with major types of chemical degradation such as carbonation, leaching and acid attacks. Conventional surface pH measurements with potentiometric flat surface electrodes have low spatial resolution, whereas optical pH visualization with indicator dyes (phenolphthalein) only indicates the areas with higher or lower pH than the pKa of the indicator. In this regard, it is key to develop wide‐range imaging systems, enabling accurate and spatially resolved determination of pH variability for an advanced knowledge of degradation mechanisms. This contribution presents the enhancements made for a high‐resolution optical pH imaging system based on fluorescent aza‐BODIPY indicator dyes. The measurement range was increased to 6 pH units (pH 6.5 to pH 12.5) by a combination of two indicator dyes. Moreover, background scattering effects were sufficiently eliminated. With the improved sensor foils steep pH gradients (up to 3 pH units within 2 mm) were successfully recorded in various concrete specimens using a macro lens reaching a resolution of down to 35 μm per pixel.

    AB - The pH of concrete‐based material is a key parameter for the assessment of its stability and durability, since a change in pH is usually associated with major types of chemical degradation such as carbonation, leaching and acid attacks. Conventional surface pH measurements with potentiometric flat surface electrodes have low spatial resolution, whereas optical pH visualization with indicator dyes (phenolphthalein) only indicates the areas with higher or lower pH than the pKa of the indicator. In this regard, it is key to develop wide‐range imaging systems, enabling accurate and spatially resolved determination of pH variability for an advanced knowledge of degradation mechanisms. This contribution presents the enhancements made for a high‐resolution optical pH imaging system based on fluorescent aza‐BODIPY indicator dyes. The measurement range was increased to 6 pH units (pH 6.5 to pH 12.5) by a combination of two indicator dyes. Moreover, background scattering effects were sufficiently eliminated. With the improved sensor foils steep pH gradients (up to 3 pH units within 2 mm) were successfully recorded in various concrete specimens using a macro lens reaching a resolution of down to 35 μm per pixel.

    KW - optical pH sensors

    KW - pH-sensitive dyes

    KW - concrete carbonation

    KW - bio-corrosion

    M3 - Article

    VL - 3

    SP - 39

    EP - 45

    JO - RILEM Technical Letters

    JF - RILEM Technical Letters

    SN - 2518-0231

    ER -