The potential of in situ Raman spectroscopy in the study of the health of cement-based materials of modern buildings during restoration works

Although Raman spectroscopy is a common technique for the analysis of cement-based materials in the research studies or in the field of Cultural Heritage to carried out multianalytical studies, it is not generally used as unique technique of a research or to carry out analysis during ordinary restoration works of modern urban buildings affected by environmental stressors. The disadvantages associated with Raman spectroscopy as fluorescence limits its implementation beyond research studies, more in the case of in situ equipment. However, the technological development allows high-quality results with in situ equipment, so its use could be useful during restoration works. Thus, this work demonstrates how the implementation of the correct methodology could lead to useful and fast results during restoration works. The proposed methodology is based on the use of in situ analysis (screening) on the scaffolding, followed by the sampling of layers based on the previous screening and a posterior exhaustive laboratory analysis. The research has been conducted during the restoration works of a reinforced concrete building in which the attack of atmospheric acid gases (CO2, SO2, and NOx) was identified as the main affection suffered, and the fixed sulfates were the most important intermediary compounds of decaying processes. Many of the pollutants and decaying compounds were even identified during the in situ analysis, improving the anticipation and responsiveness. Therefore, this methodology allows the understanding of the chemistry of the materials to evaluate its health state in a fast and reliable way.