Durability of Functionalized Carbon Structures with Optical Fiber Sensors in a Highly Alkaline Concrete Environment

Abstract

The paper presents an investigation into the durability of functionalized carbon structures (FCS) in a highly alkaline concrete environment. First, the suitability of optical fibers with different coatings-i.e., acrylate, polyimide, or carbon-for the FCS was investigated by subjecting fibers with different coatings to micro/macro bending and a 5% sodium hydroxide (NaOH) (pH 14) solution. Then, the complete FCS was also subjected to a 5% NaOH solution. Finally, the effects of spatial variation of the fiber embedded in the FCS and the bonding strength between the fiber and FCS was evaluated using different configurations -i.e., fiber integrated into FCS in a straight line and/or with offsets. All three coatings passed the micro/macro bending tests and show degradation after alkaline exposure, with the carbon coating showing least degradation. The FCS showed relative stability after exposure to 5% NaOH. The optimum bonding length between the optical fiber and the carbon filament was found to be ≥150 mm for adequate sensitivity.

Fiber Optic Sensors Embedded in Textile-Reinforced Concrete for Smart Structural Health Monitoring: A Review

“…The water in the pores of Portland cement is alkaline with a pH in the range between 12.5 and 13.5 [ 96 ]. Therefore, when functionalized TRCs are embedded into concrete, the highly alkaline environment might degrade the mechanical properties of both the optical glass fiber and the textile filaments as well as the bond between the two components, thus limiting the life-span and operation of the combined sensing and reinforcement structure.…”

“…Therefore, when functionalized TRCs are embedded into concrete, the highly alkaline environment might degrade the mechanical properties of both the optical glass fiber and the textile filaments as well as the bond between the two components, thus limiting the life-span and operation of the combined sensing and reinforcement structure. Therefore, the impact of highly alkaline concrete environments on the functionalized textile-based carbon reinforcement structure was investigated in [ 96 ]. In this study, the resistance of the functionalized textile-based reinforcement structure against the highly alkaline environments was explored depending on the coating of the optical glass fiber (acrylate, polyimide and carbon) and the tex-number of the textile filament (400, 800 and 1600 tex) of 300 mm long one-dimensional structures that have been fabricated according to the technique described in Section 4.1 [ 96 ].…”

“…Therefore, the impact of highly alkaline concrete environments on the functionalized textile-based carbon reinforcement structure was investigated in [ 96 ]. In this study, the resistance of the functionalized textile-based reinforcement structure against the highly alkaline environments was explored depending on the coating of the optical glass fiber (acrylate, polyimide and carbon) and the tex-number of the textile filament (400, 800 and 1600 tex) of 300 mm long one-dimensional structures that have been fabricated according to the technique described in Section 4.1 [ 96 ]. Moreover, in order to simulate the highly alkaline concrete environment, a 5% NaOH solution (pH 14) was used in this study and the samples were exposed to this solution over a period of three months.…”

“…Moreover, in order to simulate the highly alkaline concrete environment, a 5% NaOH solution (pH 14) was used in this study and the samples were exposed to this solution over a period of three months. From the investigation in [ 96 ], the authors deduced that optical glass fibers with carbon coating showed the best resistance against highly alkaline pore water [ 96 ]. Moreover, since PVA is used for the fabrication of the functionalized textile-based reinforcement structures (which is relatively inert against chemicals), the functionalized reinforcement structures are relatively stable against alkaline pore water attack in general [ 96 ].…”

Editorial on Special Issue “Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication”

“…For example, Bremer et al [1] reported an investigation on the feasibility of utilizing Mode Division Multiplexing (MDM) for simultaneous measurement of Surrounding Refractive Index (SRI) and temperature using a single sensor element based on an etched OM4 Graded Index Multi Mode Fiber (GI-MMF) with an integrated fiber Bragg Grating (BG). In another research article by Bremer et al [2], the durability of functionalized carbon structures (FCS) that are equipped with fiber optic sensors in a highly alkaline concrete environment are investigated. In their investigation, the suitability of optical fibers with different coatings as well as different integration techniques for the FCS were analyzed.…”