Ferruginous phases in 19th century lime and cement mortars: A Raman microspectroscopic study.

Dariz, Petra; Schmid, Thomas (2017). Ferruginous phases in 19th century lime and cement mortars: A Raman microspectroscopic study. Materials Characterization, 129, pp. 9-17. https://doi.org/10.1016/j.matchar.2017.04.009

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Raman microscopic imaging was just recently introduced into the analysis of residual Roman and Portland cement grains in 19th century cement stone, displaying evidence of the experimental adaptation of contemporary technological knowledge and practice to local circumstance. Beyond calcium ferrites, this study deals with ferruginous clinker phases that are atypical compared to present-day commercial conditions of manufacture, such as iron oxides, clinopyroxenes or pyroxenoids. Analog, microtexture, mineralogy and chemical composition of pulverized ferrosilicate slag used in the course of the 19th century as mineral additive in lime mortar reflect local resource utilization, recording the melting history within the furnace and the effectiveness of the reduction process of a single smelting event. In the case of the discussed example, chemical imaging by Raman microscopy allowed deducing a lime-rich, low-silica melt exposed to fairly reducing conditions because of the detection of the pyrometallurgic phases fayalite (Fe2SiO4), kirschsteinite (CaFeSiO4) and calcioolivine (Ca2SiO4) in zoned olivine laths and (with the melilite gehlenite, Ca2Al2SiO7) in the interstitial matrix, cross-cut by dendritic wuestite (FeO). The presented analytical approach faces the high spatial complexity of such mortar samples by microspectroscopic imaging with micrometer lateral resolution and their chemical complexity by extracting the rich chemical information content from Raman spectra. Intensity maps of marker bands provide spatial phase distributions. Furthermore, maps of peak positions can give access to the dissemination of spectroscopically similar phases of solid solution series (e.g., olivine and calcium aluminate ferrite) as well as varying amounts of incorporated foreign cations (e.g., in hematite).

Item Type:	Journal Article (Further Contribution)
Division/Institute:	Bern Academy of the Arts Bern Academy of the Arts > Institute Materiality in Art and Culture
Name:	Dariz, Petra and Schmid, Thomas
Language:	English
Submitter:	Service Account
Date Deposited:	25 Feb 2020 11:12
Last Modified:	07 Oct 2020 10:41
Publisher DOI:	https://doi.org/10.1016/j.matchar.2017.04.009
Related URLs:	Publication
ARBOR DOI:	10.24451/arbor.7155
URI:	https://arbor.bfh.ch/id/eprint/7155