Influence of citric acid on the fire behavior of gypsum coatings of construction and structural elements

[ENG] To improve the workability in gypsum plasters, additives are sometimes used, including citric acid, which provides acceptable setting times for low w/g ratios, maximizing the mechanical properties of the material. The influence of citric acid on the fire response of gypsum coatings is not well known, and so our aim was to analyze the effects that citric acid produces on the behavior of gypsum plasters exposed to fire. Temperature measurements were made with sensors and thermal imaging cameras while other instrumental techniques, including SEM, XRD and TG, were used to characterize the microstructure and composition of gypsum materials subjected to the action of fire. The fire had a greater effect on gypsum plasters containing citric acid as revealed by the cracking patterns and heat propagation profiles observed. Likewise, micro-cracks were observed in gypsum specimens, containing and non-containing citric acid, exposed to fire. In all cases, the alterations were consistent with the temperature profiles and chemical composition of the faces whether exposed to fire or not. [SPA] Influencia del ácido cítrico en el comportamiento al fuego de revestimientos de yeso de elementos constructivos y estructurales. Habitualmente, para mejorar la trabajabilidad del yeso se utilizan aditivos, entre ellos el ácido cítrico, que proporciona tiempos de fraguado aceptables para relaciones a/y bajas, potenciando al máximo las propiedades mecánicas de este material. La influencia del ácido cítrico en la respuesta frente al fuego de revestimientos de yeso no se conoce bien. El objetivo de este trabajo consiste en analizar los efectos que produce el ácido cítrico en el comportamiento frente al fuego del yeso. Para ello se usaron medidas de temperatura con sensores, cámara termográfica y otras técnicas instrumentales (SEM, XRD y TG) para caracterizar la microestructura y composición de los materiales de yeso sometidos a la acción del fuego. El fuego tuvo mayor efecto en yesos que co