Nature and origin of white efflorescence on bricks, artificial stones, and joint mortars of modern houses evaluated by portable Raman spectroscopy and laboratory analyses.

Bricks and mortar currently constitute one of the most important building materials used in the construction of most modern facades. The deterioration of these materials is caused primarily by the impact of numerous external stressors, while poor manufacturing quality, particularly of mortars, can also contribute to this process. In this work, the non-invasive Raman spectroscopy technique was used to identify the recently formed deterioration compounds (primarily sulfates and nitrates) in bricks, artificial stones, and joint mortars from detached houses in the Bilbao metropolitan area (Basque Country, North of Spain), as well as to investigate the deterioration processes taking place in these materials. Additionally, to confirm and in some cases complement the results obtained with Raman spectroscopy, SEM-EDS and XRD measurements were also carried out.