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

Research output: Contribution to journalArticleResearchpeer-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 languageEnglish
Pages (from-to)39-45
JournalRILEM Technical Letters
Volume3
Publication statusPublished - 2 Nov 2018

Fingerprint

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

Keywords

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

Cite this

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, Vol. 3, 02.11.2018, p. 39-45.

Research output: Contribution to journalArticleResearchpeer-review

@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",
month = "11",
day = "2",
language = "English",
volume = "3",
pages = "39--45",
journal = "RILEM Technical Letters",
issn = "2518-0231",
publisher = "RILEM Publications SARL",

}

TY - JOUR

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

M3 - Article

VL - 3

SP - 39

EP - 45

JO - RILEM Technical Letters

JF - RILEM Technical Letters

SN - 2518-0231

ER -