Abstract

Concrete during its service lifetime, is exposed to and also interacts with the environment (such as CO2, SO42- & Cl-), which would trigger deterioration mechanisms and subsequent durability degradation. Recent decades have witnessed an increased worldwide interest in the development and application of built-in sensor networks for the purpose of continuous Structural Health Monitoring (SHM) of concrete structures. However, the existing sensors face some challenges such as the limited long-term stability and impossibility of recalibration of some optical fibre sensors. Raman spectroscopy is a vibrational technique, demonstrating unique advantages of ‘spectroscopic fingerprint’, fast response and nondestructive nature. During the past more than 10 years, the authors have been taking the initiative to explore the potential of developing a Raman spectroscopy based optical fibre sensor system for monitoring and assessing the concrete durability on site. Two bespoke optical fibre Raman systems have been successively established, which are capable of monitoring cement chemistry and concrete durability. Furthermore, built upon the success from Portland cement-based systems, the authors have also recently extended the work to novel low-carbon cementitious materials. The minerals of the cutting edge Sulphosilicate cement, and the hydration products, especially the unique carbonation behaviour, of magnesium phosphate cement (MPC), have been systematically investigated, which has shown a great potential for recognising the hydration and carbonation mechanisms of low-carbon cementitious materials. Based on the results obtained so far, the potential of developing a Raman spectroscopy based optical fibre system for monitoring the durability of concrete structure is fully verified.

Keywords

cement, concrete, durability, novel cementitious materials, optical fibre Raman spectroscopy.

DOI

10.5703/1288284318149

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Optical Fibre Raman Spectroscopy: A Potential Novel Sensor System for Monitoring the Durability of Concrete Structure

Concrete during its service lifetime, is exposed to and also interacts with the environment (such as CO2, SO42- & Cl-), which would trigger deterioration mechanisms and subsequent durability degradation. Recent decades have witnessed an increased worldwide interest in the development and application of built-in sensor networks for the purpose of continuous Structural Health Monitoring (SHM) of concrete structures. However, the existing sensors face some challenges such as the limited long-term stability and impossibility of recalibration of some optical fibre sensors. Raman spectroscopy is a vibrational technique, demonstrating unique advantages of ‘spectroscopic fingerprint’, fast response and nondestructive nature. During the past more than 10 years, the authors have been taking the initiative to explore the potential of developing a Raman spectroscopy based optical fibre sensor system for monitoring and assessing the concrete durability on site. Two bespoke optical fibre Raman systems have been successively established, which are capable of monitoring cement chemistry and concrete durability. Furthermore, built upon the success from Portland cement-based systems, the authors have also recently extended the work to novel low-carbon cementitious materials. The minerals of the cutting edge Sulphosilicate cement, and the hydration products, especially the unique carbonation behaviour, of magnesium phosphate cement (MPC), have been systematically investigated, which has shown a great potential for recognising the hydration and carbonation mechanisms of low-carbon cementitious materials. Based on the results obtained so far, the potential of developing a Raman spectroscopy based optical fibre system for monitoring the durability of concrete structure is fully verified.