Determination of the pH and the free alkali metal content in the pore solution of concrete: Review and experimental comparison

Plusquellec, Gilles; Geiker, Mette Rica; Lindgård, Jan; Duchesne, Josée; Fournier, Benoît; Weerdt, Klaartje De

doi:10.1016/j.cemconres.2017.03.002

Cited by 201 publications

(66 citation statements)

References 37 publications

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“…Common methods to determine the pH in concrete used in science and engineering of concrete durability are destructive and can thus not provide continuous information at a certain location . The most established method in practice is based on spraying an indicator solution on a freshly exposed concrete surface .…”

Section: Application In Research and Engineeringmentioning

confidence: 99%

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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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Section: Application In Research and Engineeringmentioning

confidence: 99%

“…The accuracy is roughly one pH unit. Other approaches to determine the pH of concrete are based on crushing concrete samples and exposing them to a leaching agent . While this may yield more finely graded results than the indicator spray test, the methods are laborious and time‐consuming.…”

Section: Application In Research and Engineeringmentioning

confidence: 99%

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

Femenias

Angst

Elsener

2017

Materials & Corrosion

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“…However, this approach is laborious. Other methods to determine the pH of concrete are pore solution expression or crushing concrete samples and exposing them to a leaching agent [6,7]. While these approaches may provide more accurate results than indicator tests, they are time consuming and present difficulties at low moisture levels as well as in the presence of sharp pH gradients, where limitations regarding the minimum sample volume needed render the application of these methods impossible.…”

Section: Introductionmentioning

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.…”

Section: Introductionmentioning

confidence: 99%

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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“…The pH of Portland cement concrete is usually in the range of 12.5 to 13.8 [9][10][11][12][13][14]. Under this high alkalinity environment, the rebar surface can form a passive film that prevents the rebar from corroding.…”

Section: Introductionmentioning

confidence: 99%

Pore Solution pH for the Corrosion Initiation of Rebars Embedded in Concrete under a Long-Term Natural Carbonation Reaction

Liu¹,

Niu²,

Li³

et al. 2018

Applied Sciences

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Featured Application: The work presented in this paper is suitable for application to the evaluation of existing reinforced concrete structures in buildings, brides, and tunnels.Abstract: This paper presents an in-situ inspection and experimental investigation on the pore solution pH of concrete cover for the corrosion initiation of rebars under a long-term natural carbonation reaction. A 77-year-old steel mill was inspected, and 35 concrete column cover samples were collected to test the pH of the pore solution and phase compositions layer by layer. The variation in pH and phase compositions of the concrete along the cover depth was studied. The in-situ inspection results indicate that the rebar embedded in concrete had begun to corrode when the carbonation depth was almost less than one-third of the cover depth. The corrosion initiation of rebars embedded in concrete can occur when the pH is between 11.3 and 12.1. The pore solution pH test results and X-ray diffraction (XRD) analysis indicated that there is a semi-carbonated zone between the fully carbonated zone and the rebar. The pH of a fully carbonated zone is in a range of 8.0-9.5, and the pH of a semi-carbonated zone is between 9.5 and 12.1.

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Determination of the pH and the free alkali metal content in the pore solution of concrete: Review and experimental comparison

Cited by 201 publications

References 37 publications

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

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

PH-monitoring in mortar with thermally-oxidized iridium electrodes

Pore Solution pH for the Corrosion Initiation of Rebars Embedded in Concrete under a Long-Term Natural Carbonation Reaction

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