Abstract
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.
Highlights
RESUMEN: Influencia del ácido cítrico en el comportamiento al fuego de revestimientos de yeso de elementos constructivos y estructurales
The Technical Building Code [1] includes the normalized time-temperature curve defined in the UNE-EN 1363-1 standard [16], which has been referenced in numerous studies on the fire behavior of construction materials [17,18,19,20]
A previous X-ray diffraction (XRD) study carried out on the powdered gypsum confirmed the presence of bassanite (CaSO4·1⁄2H2O) as the main mineral phase with a much lower presence of anhydrite or anhydrous calcium sulfate (CaSO4), calcite (CaCO3) and dolomite (CaMg(CO3)2) (Figure 3)
Summary
RESUMEN: Influencia del ácido cítrico en el comportamiento al fuego de revestimientos de yeso de elementos constructivos y estructurales. Gypsum has been widely used in construction because, among other reasons, it is an inexpensive and abundant material It is one of the most environmentally acceptable binders because it requires relatively low firing temperatures to obtain the hydraulically active form (bassanite or calcium sulphate hemihydrate). The first scientific results on the thermal behavior of gypsum did not appear until the middle of the 20th century [3, 4] At this time too, the first fire tests on gypsum plasters were carried out, becoming the first comparisons with other types of construction materials (aerated concrete or cement mortar, among others) [2], even the first studies using perlite, vermiculite and sand are reported in the literature [5]. The Technical Building Code [1] includes the normalized time-temperature curve defined in the UNE-EN 1363-1 standard [16], which has been referenced in numerous studies on the fire behavior of construction materials [17,18,19,20]
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