EXAMINING THE REACTIVITY OF VOLCANIC ASH IN ANCIENT MORTARS BY USING A MICRO-CHEMICAL APPROACH

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S. Raneri
S. Pagnotta
M. Lezzerini
S. Legnaioli
V. Palleschi
S. Columbu
N.F. Neri
P. Mazzoleni

Abstract

A micro-chemical study of ancient mortars has been performed with the aim to evaluate merits and


potential of Laser-Induced Breakdown Spectroscopy (LIBS) technique in determining composition of


mixtures and evaluating the reactivity of volcanic aggregates, taking advantages from its micro-destructivity


and no sample preparation requirements.


LIBS maps have been acquired on areas of about 25 mm2 on a set of mortars suitable characterised by the


occurrence of volcanic rock fragments with a relevant range in grain size. Na, Mg, Al, Si and Ca have been


detected and raw maps have been processed using appropriate image processing and statistical methods


(i.e.: PCA, false colour images, self-organized maps).


The compositional images have been evaluated and interpreted in the light of the supporting data


obtained by classical optical microscope and SEM-EDS methods. Results evidenced the possibility to employ


LIBS for a preliminary micro-chemical characterization of mortars, revealing also the potentiality of the


method to provide compositional and spatial distribution data on aggregate grains and hydraulic phases.

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