1,721,050 research outputs found
Archaeometric reconstruction of Nuragic ceramics from Sant’Imbenia (Sardinia, Italy). Technological evolution of production process
No full textRicostruzione archeometrica delle ceramiche da S. Imbenia, AlgheroArchaeometric reconstruction of Iron Age pottery from S. Imbenia
Composición de los dorados en la fachada de la sacristía de la iglesia de S. Maria del Carmine (Pavía, Italia)
No full textTechnological features of glazed Protomajolica ware from Benevento (Italy)
No full textThe production of glazed ceramics in Italy started in 13th century, following Islamic tradition and techniques. Protomajolica samples from two medieval archaeological sites in Benevento were analyzed from mineralogical and petrographical points of view to identify and characterize the local production of fine glazed wares. Samples are represented by jugs, amphorae, bowls and dishes finely decorated and covered by thin inner and/or outer glazed surfaces. The colour of almost all the investigated sherds varies from creamy to orange even though, from the same archaeological levels, dark grey coloured ceramic fragments likely affected by overburning of the paste (kiln refuses) were collected.Optical microscopy observations, chemical (XRF) and physical (XRD) analyses allowed to reconstruct the steps of the manufacture process, and to identify a homogeneous group of samples likely belonging to a local production area of Protomajolica, a ceramic class widespread over the Central-Southern Italy between the 13th and the 15th century
Characterization of the pore system of commercial bricks for restoration: a new perspective combining 2D and 3D imaging and traditional methods.
No full textCharacterization of the pore system of commercial bricks for restoration: a new perspective combining 2D and 3D imaging and traditional methods.
No full textDuring the firing of bricks, mineralogical and textural transformations produce an artificial aggregate characterised by significant porosity. Particularly as regards pore-size distribution and the interconnection model, porosity is an important parameter to evaluate and predict the durability of bricks. The pore system is in fact the main element, which correlates building materials and their environment (especially in cases of aggressive weathering, e.g., salt crystallisation and freeze-thaw cycles) and determines their durability. Four industrial bricks with differing compositions and firing temperatures were analysed with ?direct? and ?indirect? techniques, traditional methods (mercury intrusion porosimetry, hydric tests, nitrogen adsorption) and new analytical approaches based on digital image reconstruction of 2D and 3D models (back-scattered electrons and computerised X-ray micro-Tomography). The comparison of results from different analytical methods in the ?overlapping ranges? of porosity and the careful reconstruction of a cumulative curve, allowed overcoming their specific limitations and achieving better knowledge of the pore system of bricks
CLAYS WITH NO CARBONATES IN BRICK MANUFACTURING: LINK MICROSTRUCTURAL AND MINERALOGICAL EVOLUTION TO FIRING CONDITIONS
Full text linkArchaeometric investigation and evaluation of the decay of ceramic materials from the church of Santa Maria del Carmine in Pavia, Italy.
Full text linkWe performed an archaeometric study of the ceramic materials from the façade of the church of Santa Maria del Carmine in Pavia (Italy). We obtained useful information about the firing temperatures, the provenance of raw materials and the type of oven used. The ceramics used in the façade are mineralogically rich in quartz, feldspar and phyllosilicates, and newly formed calcium silicate phases were detected in some samples. Microtextural observations revealed the presence of incipient reaction rims, phyllosilicate sintering and partial vitrification of the matrix. Ceramics show high porosity (32 to 45%) and pore sizes of between 0.4 and 1.3 µm. Our study of the different types of decay collected on the façade of the church (green and black patinas and efflorescences) revealed the presence of gypsum, whewellite, thenardite and moolooite.Se ha llevado a cabo un estudio arqueométrico de los materiales cerámicos de la fachada de la iglesia de Santa Maria del Carmine en Pavía (Italia). Se han obtenido valiosas informaciones sobre las temperaturas de cocción, la procedencia de las materias primas arcillosas y el tipo de hornos utilizados. Mineralógicamente, las cerámicas utilizadas en la iglesia son ricas en cuarzo, feldespato y filosilicatos y en algunas muestras se han detectado silicatos de calcio de neoformación. Las observaciones microtexturales han revelado la presencia de incipientes bordes de reacción, la sinterización de los filosilicatos y la parcial vitrificación de la matriz. Las cerámicas poseen una porosidad elevada (del 32 al 45%) y radio de poros comprendido entre 0,4 y 1,3 μm. El estudio de los diferentes tipos de deterioro muestreados en la fachada de la iglesia (pátinas verdes y negras y eflorescencias) ha revelado la presencia de yeso, whewellita, thenardita e moolooita
Firing and post-firing dynamics of Mg- and Ca-rich bricks used in the built heritage of the city of Padua (northeastern Italy)
Full text linkDiverse types of bricks from monuments in the city of Padua (northeastern Italy) were studied using
a multi-analytical approach based on spectrophotometry, X-ray fluorescence (XRF), X-ray powder diffraction
(XRPD), polarized-light optical microscopy (POM) and/or high-resolution scanning electron microscopy with
coupled energy-dispersive X-ray spectroscopy (HRSEM-EDS). The most representative bricks were yellow or
beige and in well-preserved condition. The results showed that they were made of Mg- and Ca-rich illitic clays,
were fired at high temperatures (from 900 to over 950 C), and achieved an incipient vitrification. Two main
processes took place during firing: (i) the development of a Ca-aluminosilicate amorphous phase where very
abundant pyroxene-type crystals were nucleated and (ii) the transformation of the pristine Mg-rich clayey grains
into Mg-silicate mineral phases. The analyses suggest a firing dynamic within a highly reactive and supersaturated
unstable system, particularly rich in calcium and magnesium. There are also signs of the rapid heating
and/or soaking of the bricks and the irregular heat distribution and/or different residence times inside the kilns.
The formation of zeolite and calcite secondary phases was also observed. The former was largely promoted by
the high calcium content of the bodies and the very humid conditions, while the latter was mainly precipitated
from Ca-rich solutions. The preservation of the bricks was enhanced by processes that took place both during
and after firing. Firstly, the significant development of a Ca-rich amorphous phase and of high-temperature
pyroxene-type crystals has provided strength to the bricks. Secondly, the porosity yielded by the firing of the
carbonate-rich clays was almost filled by secondary calcite, which acted as a cementing agent. The information
attained has increased the knowledge of (i) the mineralogical and microstructural changes that take place during
the firing over 900 C of Ca- and Mg-rich illitic clays and (ii) the formation of secondary phases within highly
calcareous bricks laid in very humid environments and affected by Ca-rich solutions. The key role of the Ca- and
Mg-rich raw clays and of the high firing temperatures, in producing high-quality bricks, and of the secondary calcite,
which increased their durability, is highlighted. All these factors have contributed to the better preservation
of the built heritage of the city
The use of mineralogical indicators for the assessment of firing temperature in fired-clay bodies
No full textFired-clay bricks are frequently object of conservative actions aimed at the preservation of cultural heritage. Information on firing conditions is relevant for the production of custom made replacement bricks, since, as a widely accepted principle, they should be close match to the pre-existing ones. In this work, the mineralogical and microstructural evolution of fired-clay bodies is described using a combination of analytical techniques, and an approach for the assessment of firing temperature using calibration curves built from the results of X-ray powder diffraction quantitative phase analysis with the Rietveld method, is presented. The weight fractions of hematite, mullite and the amorphous fraction, from two raw clays fired in the laboratory at different temperatures, have been used to assess the firing temperature of two industrially produced bricks. The values derived applying these three methods were in good agreement with the nominal temperatures of the industrial cycles. This approach might be of interest for the assessment of the firing conditions of a broader range of historical/archaeological fired-clay materials
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