The Application of Various Indicators for the Estimation of Carbonation and <i>p</i>H of Cement Based Materials

Mitchell, M. R.; Link, RE; Yu, Myoung-Youl; Lee, Jae Yong; Chung, Chul-Woo

doi:10.1520/jte102382

Cited by 13 publications

(3 citation statements)

References 8 publications

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“…For that, thymolphthalein solution was prepared by dissolving 0.04 gr of thymolphthalein in 50 mL of 95% ethanol, diluted to 100 mL of deionized water. The prepared thymolphthalein solution was sprayed on the two freshly broken mortar surfaces so the depth at pH 9-10 was determined [8]. The carbonation depth was determined from the average of 8 measurements of the depth of color change (4 measurements for each exposed surface).…”

Section: Methodsmentioning

confidence: 99%

“…Common methods to determine the pH in concrete are destructive, do not provide continuous information over time and have limited spatial resolution [6,7]. The most established method in practice is based on spraying an indicator solution [8], such as phenolphthalein or thymolphthalein, on a freshly exposed concrete surface. This test indicates the depth of carbonation, which is defined as the depth at which the pH gradient meets the indicator's characteristic pH.…”

Section: Introductionmentioning

confidence: 99%

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PH-monitoring in mortar with thermally-oxidized iridium electrodes

2017

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The pH of the concrete pore solution plays a vital role in protecting the reinforcing steel from corrosion. Here, we present results from embeddable pH sensors that permit the continuous, in-situ monitoring of the pH in the concrete pore solution. These are potentiometric sensors, based on thermallyoxidized iridium/iridium oxide (IrO x ) electrodes. We propose an iterative calculation algorithm taking into account diffusion potentials arising from pH changes, thus permitting the reliable, non-destructive determination of the pore solution pH over time. This calculation algorithm forms an essential part of the method using IrO x electrodes. Mortar samples were exposed to accelerated carbonation and the pH was monitored at different depths over time. Comparative tests were also performed using thymolphthalein pH-indicator. The results from the pH sensors give insight in the carbonation process, and can, in contrast to thermodynamic modelling and titration experiments, provide insight in kinetic processes such as transport and phases transformations. It was found that the front at which the pH is decreased from initially 13-14 down to 12.5 can be significantly ahead of the common carbonation front corresponding to pH 9-10. This has major implications for laboratory testing and engineering practice.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

PH-monitoring in mortar with thermally-oxidized iridium electrodes

2017

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“…Several authors have proposed more accurate methods (18)(19). For instance, ASTM International (20) suggested the use of thymolphthalein as a good substitute. Thymolphthalein turns from blue to colorless within an approximate pH range of 9.3 to 10.5, while phenolphthalein turns from red-violet to colorless between a pH range of 8.9 to 9.8.…”

Section: Indicatorsmentioning

confidence: 99%

A review of sample preparation and its influence on pH determination in concrete samples

Manso

Aguado

2017

Mater. construcc.

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SUMMARY:If we are to monitor the chemical processes in cementitious materials, then pH assays in the pore solutions of cement pastes, mortars, and concretes are of key importance. However, there is no standard method that regulates the sample-preparation method for pH determination. The state-of-the-art of different methods for pH determination in cementitious materials is presented in this paper and the influence of sample preparation in each case. Moreover, an experimental campaign compares three different techniques for pH determination. Its results contribute to establishing a basic criterion to help researchers select the most suitable method, depending on the purpose of the research. A simple tool is described for selecting the easiest and the most economic pH determination method, depending on the objective; especially for researchers and those with limited experience in this field. RESUMEN:Revisión sobre la preparación de muestras de hormigón y su influencia sobre la determinación del pH. Determinar el pH de la fase acuosa de los poros de pastas de cemento, morteros y hormigones tiene gran importancia en el monitoreo de los procesos químicos que tienen lugar en los materiales cementiceos. Sin embargo, no existe una normativa que regule el método de preparación de la muestra para la determinación de su pH. Este artículo presenta un estado del conocimiento de diferentes metodologías para la determinación del pH de materiales cementiceos y la influencia del método de preparación según el objetivo. Además, se presenta una campaña experimental comparando tres técnicas diferentes. Dicha campaña contribuye a establecer un criterio simple que ayude al investigador en la selección del método más adecuado dependiendo del objeto de studio. Este artículo tiene por objetivo ser una herramienta sencilla para seleccionar la metodología más fácil y económica para determiner el pH dependiendo del objetivo, especialmente para investigadores noveles o aquellos con escasa experiencia.

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Monitoring pH in corrosion engineering by means of thermally produced iridium oxide electrodes

Femenias

Angst

Elsener

2017

Materials & Corrosion

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Funding information Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen ForschungA pH sensor to be used in highly alkaline media under continuous long-term immersion conditions is crucial in various engineering applications. This work develops the production protocol and posterior conditioning of thermally oxidized iridium (IrO x ) electrodes to be used as potentiometric pH sensors embedded in highly alkaline environments such as concrete or cathodically protected steel in soil. The main investigated aspects for the desired applications are the potential-pH response, its reproducibility, accuracy, and oxygen dependency. The stability during long-term immersion is also studied in detail. The studied IrO x electrodes responded to pH changes with slopes between −50 and −68 mV/pH unit, even after continuous immersion in alkaline solutions for almost 2 years. Additionally, the electrodes response did not show oxygen dependency. Our results highlight the importance of sufficient conditioning in alkaline media prior to use. When properly produced, conditioned, and pre-calibrated the electrodes reproducibly permit measuring the pH with a maximum error of 0.5 pH units over a range of at least pH 9-13.5. Preliminary results show that the studied electrodes are promising sensors for monitoring pH changes in concrete.

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The Application of Various Indicators for the Estimation of Carbonation and pH of Cement Based Materials

Cited by 13 publications

References 8 publications

PH-monitoring in mortar with thermally-oxidized iridium electrodes

PH-monitoring in mortar with thermally-oxidized iridium electrodes

A review of sample preparation and its influence on pH determination in concrete samples

Monitoring pH in corrosion engineering by means of thermally produced iridium oxide electrodes

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