Clay minerals in historic buildings

Although identified in heritage stones, clays are not always taken into full account in terms of negative effects due to their swelling ability (Delgado Rodrigues, Materiales de Construccin 51:183-195, 2001). The main purpose of this study is to identify clays in welded tuffs of three different historic monuments located in the city of Guanajuato, Mexico, and to establish the clays' contribution to the deterioration of the monuments by their swelling behavior. Thermal analysis, differential thermal analysis (DTA), thermogravimetry (TG), and dynamic mechanical analysis (DMA), as well as supplementing data with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM), have been used. Data suggest that clays present in welded tuffs of the historic monuments studied contribute to increased deterioration through osmotic swelling in two of the three monuments.