Study by Thermal Analysis of Mortars Belonging to Wall Paintings Corresponding to Some Historical Buildings of Sevillian Art

Abstract

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 hydRaúlic, so much by results from ratios between mass loss due to CO2 and H2O, hydRaúlic 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.