Authors:J. L. Perez-Rodriguez, A. Duran, and L. A. Perez-Maqueda
In this study, the decomposition behaviour of unaltered and altered dolomitic rock samples used in Cultural Heritage buildings was studied by simultaneous TG–DTA experiments at different atmospheres, X-ray diffraction in a high-temperature chamber, and evolved gas analysis. The components of dolomite rock samples and hydrated calcium oxalate formed during the alteration processes of the rocks were characterized, and the decomposition mechanisms of these components were determined. The TG–DTA experiments carried out at CO2 atmosphere were used to determine the carbonate compounds in the rock samples. The TG–DTA study characterized the presence of organic compounds formed during the biological degradation of the rock samples, possibly responsible of the hydrated calcium oxalate formation.
Authors:A. Duran, L. Perez-Maqueda, J. Poyato, and J. Perez-Rodriguez
Roman ancient mortars have been widely studied, in connection with both diagnosis and application required for restoring.
Thermoanalytical experiments performed on mortars from Pompeii and Herculaneum provided a very good understanding of the technology
employed. The mortars from Pompeii were obtained by the proper mixing of lime and marble grains while mortars of Herculaneum
by lime and silicates compounds. The position of the endothermic peak of calcite decomposition showed important variations
in the different samples studied, which was assigned to the different crystallinity and particle sizes. Experiments under
CO2 flow confirmed the presence of magnesium calcium carbonates.
Authors:A. Duran, M. Robador, M. Jimenez de Haro, and Veronica Ramirez-Valle
Mortars taken from the walls of three historical buildings in Seville: Pond of Patio de las Doncellas in Real Alcazar of Seville,
the Monastery of Santa Maria de las Cuevas and the Church of El Salvador were investigated.
The techniques employed were thermogravimetry (TG), differential thermal analysis (DTA), XRD, FTIR, SEM with EDAX, Bernard
calcimeter, granulometry, mercury intrusion porosimetry and mechanical strength tests.
The majority of the studied mortars consist of calcite and silica. Gypsum was detected in samples of four mortars from the
Santa Maria de las Cuevas Monastery and two from the El Salvador Church, whose samples were taken from the upper layers of
the walls, but gypsum was not detected in the internal mortars layers. Only in two of the samples of the Monastery, the presence
of cellulosic material as an organic additive was detected.
All the studied mortars could be regarded hydraulic, so much by results from ratios between mass loss due to CO2 and H2O, hydraulic module and assays of compressive strength. The values obtained by these three techniques are related, providing
good agreements between them.
These results give useful information that aids in understanding the technology of historic mortars, and how to plan the restoration
of these wall paintings.
Authors:M. Franquelo, M. Robador, V. Ramírez-Valle, A. Durán, M. Jiménez de Haro, and J. Pérez-Rodríguez
Roman ceramics of two hydraulic mortars used to build the pond and water channel of Mithraeum house from Mérida (Spain) have
been studied. The sizes of the ceramic fragments found were different in both of the samples studied, showing different behaviour
in the reactions with the lime. The X-ray diffraction of the ceramic shows the presence of quartz, mica (biotite), anorthite
and hematite accompanied by amorphous phase, being observed scarce vitrification. The presence of mica confirms a firing temperature
for manufacturing the ceramic below 900°C. In one of the ceramics studied, X-ray diffraction did not show calcite. However,
in the FTIR appear bands that could be assigned to carbonates absorptions and likewise, carbonates were identified in the
DTA-TG curves. Ca and small quantities of Si and Al were also identified by SEM-EDX on the surface of the pores that could
be due to an amorphous phase formed in the reaction of lime with the Si and Al of the ceramic. On the other hand, in other
ceramic samples carbonates (about 10%) were detected. The carbonates have been found filling the pores, sometimes accompanied
by a new calcium-aluminium-silicate phase produced by the reaction between the lime and the amorphous phase of the ceramic.
The carbonates and the new phases formed inside the pores are responsible for the decrease of the porosity and for the formation
of new phases during the heating of the ceramics.
Authors:V. Ramírez-Valle, M. Jiménez de Haro, M. Avilés, L. Pérez-Maqueda, A. Durán, J. Pascual, and J. Pérez-Rodríguez
Static and dynamic heating
of vermiculite samples from Santa Olalla, Huelva, Spain, saturated with different
cations, i.e. Na+, Cs+,
Ca2+, Ba2+ and Al3+,
have been studied. The characterization of the phases formed during heating
has been carried out by X-ray diffraction. The phases formed depend on the
cation present in the interlamellar position and the heating process. The
phases identified in the vermiculite samples saturated with different cations
and heated at different temperatures are the following: enstatite, forsterite,
spinel, cordierite, anorthite, pollucite, nepheline, coesite, celsian and
others various mixed silicates; also some dehydrated and amorphous phases
have been observed. On static heating, at the maximum temperature reached
in this work, the phases formed appear mixed with a glassy phase.