Caracterización físico-química de pigmentos minerales aplicados a soportes elaborados con componentes ancestrales, mediante análisis instrumental

Abstract

The use of current aesthetic coating products in earthen buildings has generated structural problems due to their low permeability, since a gas exchange is generally required to avoid the accumulation of internal humidity. Therefore, the use of paints based on mineral pigments is considered more appropriate, since it provides adequate permeability and avoids damage to the structure. For this reason, this project aims to analyze the coupling of mineral paint and coating or finishes in earthen structures. For this purpose, the structure of an earthen wall was imitated by placing the revoque, pañete and calcium carbonate or lime as a conditioning base in a container. Subsequently, a visual analysis was performed during and after the application of the mineral paint, in addition, instrumental techniques such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet Visible Spectroscopy (UV-vis) were used in order to determine the physical-chemical characteristics of the pigment, in addition, a pH analysis was incorporated. The results obtained showed that, on calcium carbonate surfaces, the mineral paint has a good finish compared to lime surfaces. Among the components of the applied paint, quartz, alumina (Al2O3), kaolinite, hematite, calcium carbonate and goethite were identified by XRD, OH groups, silicates, Si-O, Fe-O and quartz by FTIR, hematite in the form of elongated rods by SEM and by UV-vis it was established that the chromophore group causing the red color in this mineral pigment is produced by iron minerals, such as hematite. The pH analysis identified a value of 7.12 close to neutral in carbonate supports, while in lime it was 11.04 alkaline with the formation of Ca(OH)2.