A fiber Bragg grating sensor for detection of liquid water in concrete structures

Concrete structures rely greatly on the integrity of their supporting rebars to remain serviceable for their intended purposes. Unfortunately, rebars are vulnerable to corrosion due to the ingress of water from the environment, which often also carries a multitude of ionic particles that encourage corrosion. Liquid phase water may enter the structure through cracks that may not be obvious to human observation. Thus, a fiber Bragg grating sensor was designed that is able to detect (i.e. ‘on‐off’) the presence of liquid water in order to provide an early warning signal for the ingress of water. Two tests were conducted to verify the functionality of the sensor: the first experiment tested the repeatability of the sensor to cyclic input of various volumes of water, and the second tested the sensor’s response to flooding conditions. The sensor showed a good repeatability, with fast response times (<10 min to reach a level guaranteeing the presence of water) and a recovery time of 11‐15 h, depending on the input volume. The flooding test showed similar performance and viability of the sensor during flooding conditions. (Some figures may appear in colour only in the online journal)

[1]  W. Doane,et al.  A Practical Process for the Preparation of Super Slurper, a Starch‐Based Polymer with a Large Capacity to Absorb Water , 1977 .

[2]  Quan Zhou,et al.  Porous fiber-optic sensor for high-sensitivity humidity measurements , 1988 .

[3]  Otto S. Wolfbeis,et al.  Optical sensors, 13: fibre-optic humidity sensor based on fluorescence quenching , 1988 .

[4]  F. Mitschke.  Fiber-optic sensor for humidity. , 1989, Optics letters.

[5]  Swelling and Shrinking Processes of Sodium Polyacrylate-Type Super-Absorbent Gel in Electrolyte Solutions , 1990 .

[6]  Yoshiro Sakai,et al.  Optical humidity sensing characteristics of Nafion—dyes composite thin films , 1992 .

[7]  G. Lindner,et al.  PVDF-excited resonance sensors for gas flow and humidity measurements , 1994 .

[8]  Eric Udd,et al.  An overview of fiber‐optic sensors , 1995 .

[9]  G. Visscher,et al.  Standard psychrometers: a matter of (p)references , 1995 .

[10]  Enrico Traversa,et al.  Ceramic sensors for humidity detection: the state-of-the-art and future developments , 1995 .

[11]  M. Haruta,et al.  Humidity-sensitive optical absorption of Co3O4 film , 1996 .

[12]  Joseph R. Stetter,et al.  Comparison of conductometric humidity-sensing polymers , 1997 .

[13]  Jörg-Uwe Meyer,et al.  Thick-film humidity sensor based on porous material , 1997 .

[14]  Karol Nitsch,et al.  Thick-film humidity sensors , 1997 .

[15]  Mohd Nasir Taib,et al.  Extending the range of a fibre-optic relative-humidity sensor , 1997 .

[16]  T. Taguchi,et al.  A Novel Fiber-Optic Gas Sensing Arrangement Based on an Air Gap Design and an Application to Optical Detection of Humidity , 1998 .

[17]  Mingzhu Liu,et al.  Preparation and swelling properties of crosslinked sodium polyacrylate , 2001 .

[18]  F. Hua,et al.  Synthesis of self-crosslinking sodium polyacrylate hydrogel and water-absorbing mechanism , 2001 .

[19]  Kangsheng Chen,et al.  Fiber optic Bragg grating sensor based on hydrogels for measuring salinity , 2002 .

[20]  Z. M. Rittersma,et al.  Recent achievements in miniaturised humidity sensors—a review of transduction techniques , 2002 .

[21]  Shufang Luo,et al.  Applications of LPG fiber optical sensors for relative humidity and chemical-warfare-agents monitoring , 2002, SPIE/COS Photonics Asia.

[22]  S. James,et al.  Optical fibre long-period grating sensors: characteristics and application , 2003 .

[23]  Masayuki Morisawa,et al.  A plastic optical fibre sensor for real-time humidity monitoring , 2003 .

[24]  Dukjoon Kim,et al.  Theoretical and experimental investigation of the swelling behavior of sodium polyacrylate superabsorbent particles , 2003 .

[25]  Simultaneous monitoring of the corrosion activity and moisture inside aircraft lap joints , 2004 .

[26]  Sean G. Calvert,et al.  Implementing fiber optic sensors to monitor humidity and moisture , 2004, SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[27]  T. L. Yeo,et al.  Characterisation of a polymer-coated fibre Bragg grating sensor for relative humidity sensing , 2005 .

[28]  Kenneth T. V. Grattan,et al.  Demonstration of a fibre-optic sensing technique for the measurement of moisture absorption in concrete , 2006 .

[29]  Kenneth T. V. Grattan,et al.  Monitoring Ingress of Moisture in Structural Concrete Using a Novel Optical-Based Sensor Approach , 2006 .

[30]  Kefa Cen,et al.  Low-cost relative humidity sensor based on thermoplastic polyimide-coated fiber Bragg grating , 2007 .

[31]  T. L. Yeo,et al.  Fibre-optic sensor technologies for humidity and moisture measurement , 2008 .

[32]  Polymer-Coated Fiber Bragg Grating Sensors for Simultaneous Monitoring of Soluble Analytes and Temperature , 2009 .

[33]  Chuji Wang,et al.  Fiber Loop Ringdown — a Time-Domain Sensing Technique for Multi-Function Fiber Optic Sensor Platforms: Current Status and Design Perspectives , 2009, Sensors.

[34]  Chamini Herath,et al.  High-sensitivity fiber-loop ringdown evanescent-field index sensors using single-mode fiber. , 2010, Optics letters.

[35]  Malik Kaya,et al.  Reproducibly reversible fiber loop ringdown water sensor embedded in concrete and grout for water monitoring , 2013 .