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

doi:10.21809/rilemtechlett.2018.72

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

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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.

Original language	English
Pages (from-to)	39-45
Journal	RILEM Technical Letters
Volume	3
DOIs	https://doi.org/10.21809/rilemtechlett.2018.72
Publication status	Published - 2 Nov 2018

Keywords

optical pH sensors
pH-sensitive dyes
concrete carbonation
bio-corrosion

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10.21809/rilemtechlett.2018.72Licence: CC BY 4.0

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@article{e0e31df189c149ada8a8f44b9623fd69,

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. ",

keywords = "optical pH sensors, pH-sensitive dyes, concrete carbonation, bio-corrosion",

author = "Bernhard M{\"u}ller and Cyrill Grengg and Viktor Schallert and Marlene Sakoparnig and Christoph Staudinger and Johanna Breininger and Florian Mittermayr and Birgit Ungerb{\"o}ck and Sergey Borisov and Martin Dietzel and Torsten Mayr",

year = "2018",

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doi = "10.21809/rilemtechlett.2018.72",

language = "English",

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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

PY - 2018/11/2

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

U2 - 10.21809/rilemtechlett.2018.72

DO - 10.21809/rilemtechlett.2018.72

M3 - Article

SN - 2518-0231

VL - 3

SP - 39

EP - 45

JO - RILEM Technical Letters

JF - RILEM Technical Letters

ER -

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

Abstract

Keywords

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