Study of capillary absorption kinetics by X-ray CT imaging techniques: a survey on sedimentary rocks of Sicily

Tiziano Schillaci, Maria Brai, Antonio Cimino, Antonio Lo Casto, Fortunato Sorrentino

Abstract


Sedimentary rocks are natural porous materials with a great percent of microscopic interconnected
pores: they contain fluids, permitting their movement on macroscopic scale. Generally, these rocks
present porosity higher then metamorphic rocks. Under certain points of view, this feature represents
an advantage; on the other hand, this can constitute an obstacle for cultural heritage applications,
because the porosity grade can lead to a deterioration of the lapideous monument for water
capillary absorption.
In this paper, CT (Computerized Tomography) image techniques are applied to capillary absorption
kinetics in sedimentary rocks utilized for the Greek temples as well as baroc monuments, respectively
located in western and southeastern Sicily. Rocks were sampled near the archaeological
areas of Agrigento, Segesta, Selinunte and Val di Noto. CT images were acquired at different times,
before and after the water contact, using image elaboration techniques during the acquisition as well
as the post-processing phases. Water distribution into porous spaces has been evaluated on the
basis of the Hounsfield number, estimated for the 3-D voxel structure of samples. For most of the
considered samples, assumptions based on Handy model permit to correlate the average height of
the wetting front to the square root of time. Stochastic equations were introduced in order to
describe the percolative water behavior in heterogeneous samples, as the Agrigento one.
Before the CT acquisition, an estimate of the capillary absorption kinetics has been carried out by
the gravimetric method. A petrographical characterization of samples has been performed by stereomicroscope
observations, while porosity and morphology of porous have been surveyed by SEM
(Scanning Electron Microscope) images. Furthermore, the proposed methods have also permitted
to define penetration depth as well as distribution uniformity of materials used for restoration and
conservation of historical monuments.

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DOI: 10.6092/issn.1973-9494/1401

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Copyright (c) 2008 Tiziano Schillaci, Maria Brai, Antonio Cimino, Antonio Lo Casto, Fortunato Sorrentino

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