PSI - Issue 64

Jian-Neng Wang et al. / Procedia Structural Integrity 64 (2024) 1605–1612 / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 7. (a) Transmission spectra of sensing different pHs of the standard solutions; (b) Enlarged Transmission spectra of sensing different pHs of the standard solutions (500-800 nm).

Fig. 8. Plot of the maximum intensity (counts) versus different pHs of the standard solutions.

4. Conclusion and recommendation 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. We have constructed an optical fiber Mach-Zehnder interferometer (MZI) sensing platform for monitoring chloride ion concentrations as well as an optical fiber pH system using UV-NIR spectrometer for sensing the pH of concrete structures, respectively. 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 range from 0.015% to 12.5% (150~125000 ppm) 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 (fiber type: VIS-NIR and fiber core diameter: 400 μ m), a CUV-UV cuvette holder, a broadband light source (200 ― 1100 nm), an UV-NIR spectrometer (HR 4000 UV-NIR), and a personal computer for data acquisition. We measured different pHs of the standard solution with different pHs of 1, 4.08, 4.95, 5.99, 7.09,