Raman Microspectroscopic Imaging of Binder Remnants in Historical Mortars Reveals Processing Conditions
Thomas Schmid|Petra Dariz
Binder remnants in historical mortars represent a record of the connection between raw materials that enter kiln, process parameters, and end product calcination. Raman microspectroscopy combines high structural sensitivity with micrometre to sub-micrometre spatial resolution compatibility conventional thin-sectional samples an almost unique fashion, making it interesting complementary extension existing methodological arsenal for mortar analysis. spectra are vibrational fingerprints crystalline amorphous compounds, contain marker bands specific minerals their polymorphic forms. Relative intensities related same species change according crystal orientations, band shifts can be caused by incorporation foreign ions into lattices, as well stoichiometric changes within solid solution series. Finally, variations crystallinity affect widths. These effects demonstrated based on analysis three samples: micrometric distribution maps phases polymorphs, compositional series unreacted clinker grains Portland cement two 19th century castings, crystallinities thermal anhydrite clusters high-fired medieval gypsum measure applied burning temperature were successfully acquired.
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