The use of Raman spectroscopy to monitor phase changes in concrete following high temperature exposure

Concrete is one of the most widely used construction materials, having excellent mechanical properties, but may fail in a catastrophic manner post fire. In this study, we present non-destructive Raman testing of concrete walls post fire to track temperature exposure based on the decomposition of the calcium silicate hydrate (CSH) phase. The use of Raman spectroscopy is contrasted with X-ray diffraction to demonstrate its competence in evaluating thermal damage to concrete. It was found that Raman spectroscopy was more adept at identifying the hydrated phases than XRD. Principal component analysis was applied to the Raman data to demonstrate the ability of Raman spectroscopy to distinguish concrete exposed to different temperatures. The decomposition of Calcium silicate hydrate could be followed by Raman monitoring the shifts at 1081, 709 and 278 cm−1. At the highest temperature in this study (950 °C) Raman spectra showed the disappearance of these bands with formation of a new one at 1007 cm−1 attributed to the formation of gehlenite following the matrix decomposition