PSI - Issue 64

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000–000 Available online at www.sciencedirect.com Procedia Structural Integrity 64 (2024) 1605–1612

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www.elsevier.com/locate/procedia

SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Optical fiber sensing for monitoring chloride ion concentration and pH in concrete structures SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Optical fiber sensing for monitoring chloride ion concentration and pH in concrete structures

Jian-Neng Wang a,1 , Pei-Hsuan Wu a Jian-Neng Wang a,1 , Pei-Hsuan Wu a

a National Yunlin University of Science and Technology, Douliou, Taiwan (Republic of China)

a National Yunlin University of Science and Technology, Douliou, Taiwan (Republic of China)

Abstract This paper presents the development and assessment of two individual optical fiber sensing systems either for monitoring chloride concentration or pH range in structural health monitoring of concrete structures. Excessive chloride ions possess the ability to corrode the steels of reinforced concrete structures that affect the safety and health of concrete structures. In addition, the pH of concrete structures decreases to a value close to 9.5 that externally exhibits carbonation and durability problems. The optical fiber Mach-Zehnder interferometer (MZI) sensing platform setup for chloride ion concentrations and the spectral responses of the MZI for the aqueous samples of fresh concrete supernatant (W/C = 0.35 and W/C = 0.65) with salt water solutions in different concentration ranges from 0.015% to 12.5% were measured. An optical fiber pH sensing system is proposed to implement structural health monitoring of concrete especially in pH measurement, which is composed of a fiber optical sensing system with a Visible-NIR bifurcated fibers, a CUV-UV cuvette holder, a broadband light source, a HR 4000 UV-NIR spectrometer, and a personal computer for data acquisition. We measured different pHs of the standard solutions with different pHs of 1, 4.08, 4.95, 5.99, 7.09, 8.07, 9.75. The optical fiber MZI sensing platform has shown the capacity for monitoring of chloride ion concentrations in the ranges from 150 ppm to 125000 ppm. A linear fit (adj. R-Square = 0.87207 and 0.97876 for fresh concrete supernatant with W/C = 0.35 and W/C = 0.65, respectively) for the graph of sensing response, light intensity or transmission loss, as a function of the chloride solution concentration for this 8-cm MZI sensor. Furthermore, based on the optical fiber pH sensing results, we found a linear increase in the maximum intensity (counts) as the pH of standard solution increased from1 to 9.75 (adj. R-Square = 0.91367). © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers Keywords: optical fiber; chloride ion concentration; Mach-Zehnder interferometer; pH; concrete Abstract This paper presents the development and assessment of two individual optical fiber sensing systems either for monitoring chloride concentration or pH range in structural health monitoring of concrete structures. Excessive chloride ions possess the ability to corrode the steels of reinforced concrete structures that affect the safety and health of concrete structures. In addition, the pH of concrete structures decreases to a value close to 9.5 that externally exhibits carbonation and durability problems. The optical fiber Mach-Zehnder interferometer (MZI) sensing platform setup for chloride ion concentrations and the spectral responses of the MZI for the aqueous samples of fresh concrete supernatant (W/C = 0.35 and W/C = 0.65) with salt water solutions in different concentration ranges from 0.015% to 12.5% were measured. An optical fiber pH sensing system is proposed to implement structural health monitoring of concrete especially in pH measurement, which is composed of a fiber optical sensing system with a Visible-NIR bifurcated fibers, a CUV-UV cuvette holder, a broadband light source, a HR 4000 UV-NIR spectrometer, and a personal computer for data acquisition. We measured different pHs of the standard solutions with different pHs of 1, 4.08, 4.95, 5.99, 7.09, 8.07, 9.75. The optical fiber MZI sensing platform has shown the capacity for monitoring of chloride ion concentrations in the ranges from 150 ppm to 125000 ppm. A linear fit (adj. R-Square = 0.87207 and 0.97876 for fresh concrete supernatant with W/C = 0.35 and W/C = 0.65, respectively) for the graph of sensing response, light intensity or transmission loss, as a function of the chloride solution concentration for this 8-cm MZI sensor. Furthermore, based on the optical fiber pH sensing results, we found a linear increase in the maximum intensity (counts) as the pH of standard solution increased from1 to 9.75 (adj. R-Square = 0.91367). © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers Keywords: optical fiber; chloride ion concentration; Mach-Zehnder interferometer; pH; concrete © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers

1 * Corresponding author. Tel.: +886-5-534260-4723; fax: +886-5-5312049. E-mail address: wangjn@yuntech.edu.tw 1 * Corresponding author. Tel.: +886-5-534260-4723; fax: +886-5-5312049. E-mail address: wangjn@yuntech.edu.tw

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers 10.1016/j.prostr.2024.09.415 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers