Gypsum decay simulation: Risco de las cuevas case study, Madrid, Spain

Abstract

Since troglodyte population has excavated their dwellings in the gypsum escarpment of the Risco de las Cuevas of Perales de Tajuña (Spain), atmospheric processes have preferentially sculptured the rockwall. This weathering has a negative effect on the future of the monument, and to preserve it, it is important to investigate how the different content of clay in the gypsum that constitute the escarpment, respond to the weathering. Three types of gypsum, with different amounts of clay, material that constitute El Risco de las Cuevas, were subjected to accelerated ageing tests in laboratory (freezing/thawing and wetting/drying). In addition to laboratory observations, results from field observations and digital photogrammetry were obtained, serving to draw the geometry of the escarpment, comparing with old photographs, taken by neighbors of the village of Perales de Tajuña, in which images of the detached tape bock of gypsum can be seen, their dimensions and volume. All artificial accelerated ageing tests have leaded to gypsum caused decay, being the most aggressive the resistance to freezing in the gypsum specimens with the highest clay content.