High-resolution optical pH imaging of concrete exposed to chemically corrosive environments

Grengg, Cyrill; Müller, Bernhard; Staudinger, Christoph; Mittermayr, Florian; Breininger, Johanna; Ungerböck, Birgit; Borisov, Sergey M.; Mayr, Torsten; Dietzel, Martin

doi:10.1016/j.cemconres.2018.10.027

Cited by 35 publications

(37 citation statements)

References 15 publications

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“…Another improvement of the method is the application of an alternative reference material. Cr-GAB was used, since it shows a better spectral overlap with the pH sensitive dyes (figure 2), compared to the previously used Egyptian Blue [21]. As Cr-GAB inhibits a lower brightness than Egyptian Blue, four times the amount was used.…”

Section: Improvement Of the Imaging Methodsmentioning

confidence: 99%

“…The used set-up has been recently described by Grengg & Müller et al [21]. In brief, a sensor foil is soaked in 150 mM NaCl solution and placed on a planar concrete surface (figure 1).…”

Section: Measurement Set-upmentioning

confidence: 99%

“…For each calibration point the sensor foil was soaked in buffer, placed under the camera on a black background within the focus of the lens, and pictures were taken. Data processing is done as described by Grengg & Müller et al [21]. The mean ratiometric value of each picture is plotted against the appropriate pH value and the resulting curve is fitted using the Boltzmann equation equation 1to gain the calibration function:…”

Section: Calibration Background Evaluation and Measurementsmentioning

confidence: 99%

“…The diagnostic bands were characterized in solution (artificial pore solution + T F PLPT and PHPHT) at various pH levels via transmittance spectroscopy prior to the measurement. Understanding the potential of optical pH imaging on cementitious materials, we were able to report on a pH imaging system based on timedomain dual lifetime referencing (t-DLR) [20] utilizing aza-BODIPYs as fluorescent pH indicator dyes [21]. This methodology used a SensiCam from PCO (https://www.pco.de/) for read-out, a red excitation source and an inert, phosphorescent, reference pigment (Egyptian Blue).…”

Section: Introductionmentioning

confidence: 99%

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

Müller¹,

Grengg²,

Schallert³

et al. 2018

RILEM Tech Lett

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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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Section: Improvement Of the Imaging Methodsmentioning

confidence: 99%

“…The used set-up has been recently described by Grengg & Müller et al [21]. In brief, a sensor foil is soaked in 150 mM NaCl solution and placed on a planar concrete surface (figure 1).…”

Section: Measurement Set-upmentioning

confidence: 99%

Section: Calibration Background Evaluation and Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Müller¹,

Grengg²,

Schallert³

et al. 2018

RILEM Tech Lett

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“…e hydration process of concrete mixed with fly ash is as follows: First, cement clinker hydration precipitates Ca(OH) 2 diffuse to the surface of fly ash spherical vitreous bodies through liquid phase diffusion [45]. Subsequently, chemisorption and erosion occur, producing Ca(OH) 2 , ettringite (AFt), and CSH gel randomly.…”

Section: Scanning Electron Microscopy (Sem)mentioning

confidence: 99%

Experimental Investigation of Neutralisation of Concrete with Fly Ash as Fine Aggregate in Freeze-Thaw Environment

Zhang

Mao

Yang

et al. 2019

Advances in Civil Engineering

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To study the durability of concrete with fly ash as fine aggregate under alternate freeze-thaw and carbonation, freeze-thaw and carbonation cyclic tests are conducted to explore variation characteristics such as relative dynamic modulus of elasticity and neutralisation depth. The influence coefficient (λC) of carbonation on concrete freeze-thaw damage and the influence coefficient (λF) of freeze-thaw on concrete neutralisation are introduced. In addition, scanning electron microscopy is performed to reveal the deterioration mechanism of the alternating effect. Finally, through a regression analysis of test data, the mathematical expression of the composite damage coefficient kF under alternate freeze-thaw and carbonation is obtained. Based on these findings, a prediction model of the neutralisation depth of concrete is established with number of freeze-thaw cycles and water-cement ratio as parameters. The values calculated through this model and the values measured in the tests are highly correlated. This provides a theoretical reference and basis for the analysis of concrete durability in a multifactor environment.

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Optical sensors for the durability assessment of cement‐based infrastructure

Grengg,

Müller,

Zögl

et al. 2023

ce papers

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The corrosion‐related damages on concrete infrastructure account globally for several billion US dollars annually. Up to 38 % of these costs could be saved by the application of optimized materials and/or more efficient monitoring technologies. In this contribution a novel sensor technology is presented, based on luminescent pH sensitive dyes, to quantitatively determine the pH distribution in cement‐based construction materials. Different sensor platforms were explored resulting in high‐resolution imaging techniques, as well as in miniaturized sensor probes for field application and in situ monitoring. To this point, pH sensors were successfully applied for cementitious materials to (i) quantitatively characterize the carbonation state in the lab, (ii) gain further understanding on phase assemblages and internal pH evolution related to carbonation, (iii) reveal that the actual pH at the inflection point of phenolphthalein may strongly vary depending on physicochemical material properties, (iv) monitor the pH evolution during the early hydration of different cementitious materials, and (v) measure carbonation depths using miniaturized sensor probes adopted for field applications.

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High-resolution optical pH imaging of concrete exposed to chemically corrosive environments

Cited by 35 publications

References 15 publications

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

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

Experimental Investigation of Neutralisation of Concrete with Fly Ash as Fine Aggregate in Freeze-Thaw Environment

Optical sensors for the durability assessment of cement‐based infrastructure

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