Raman microspectroscopic imaging of binder remnants in historical mortars reveals processing conditions.

Dariz, Petra (2019). Raman microspectroscopic imaging of binder remnants in historical mortars reveals processing conditions. Heritage, 2(2), pp. 1662-1683. MDPI 10.3390/heritage2020102

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

Item Type:

Journal Article (Original Article)

Division/Institute:

Bern University of the Arts
Bern University of the Arts > Institute Materiality in Art and Culture

Name:

Dariz, Petra

Subjects:

Q Science > Q Science (General)
Q Science > QD Chemistry
Q Science > QE Geology

Publisher:

MDPI

Language:

English

Submitter:

Petra Dariz

Date Deposited:

05 Feb 2021 11:55

Last Modified:

05 Feb 2021 11:55

Publisher DOI:

10.3390/heritage2020102

Uncontrolled Keywords:

cement clinker remnants; polymorphic transitions; striations; remelted belite; high-fired gypsum; thermal anhydrite; pyrometamorphism; spectroscopic imaging; Raman microscopy

ARBOR DOI:

10.24451/arbor.13638

URI:

https://arbor.bfh.ch/id/eprint/13638

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