Caracterização e estudo do potencial de uso do residuo de gesso para a fabricação de gesso acartonado (drywall)

Abstract

Gypsum is an industrial mineral produced worldwide. It is estimated that the generation of gypsum waste exceeds the amount of 15 million tons, which are dumped in landfills; furthermore, there are many other environmental impacts related to its production, usage and dumping. In view of the growing inclusion and influence of sustainability in the civil industries, the National Environment Council - CONAMA Resolution 307/2002), reclassified the plaster waste to Class B - waste that can be recycled to other destinations. In this way, this work proposes to investigate a new alternative for the reuse of gypsum residues, from the production of a drywall sealing element, without calcination, evaluating physical, mechanical, and microstructural properties. The raw materials used were kraft paper, plaster glue, commercial gypsum, and gypsum waste. The residue was comminuted and processed in a disc mill. The powders were characterized by XRF, XRD and laser granulometer. The XRF revealed the percentage of SO3 and CaO, which have limits determined by the standard. The XRD revealed to us the phases both qualitatively and quantitatively, indicating the quality of the material that resulted in the waste as well as the hydration process. The granulometry helped to determine the water/gypsum ratio for making the boards, which had the following variables: thickness of 9.5 and 15.0 mm, weight of 0 and 70 kg during molding, and curing temperature at 25° C and 50°C. The different boards were analyzed according to their geometric and visual characteristics, surface density, flexural strength, and SEM/EDS. The geometric and visual characteristics exposed the character of shrinkage, which was associated with the appearance of defects and influence on the boards interface. The surface density indicated to us how much the grain size of the gypsum residue (7,98 μm) can influence this characteristic, as well as the flexural strength. In the SEM/EDS analysis, it was observed the interface and its adhesion, the microstructure of the plaster residue resembling that of the commercial plaster, and also indicated the concentration of the components along the boards, mainly sulfur (S) and calcium (Ca), which are the main elements of the composition of plaster and gypsum. All these results indicate the possibility of reusing plaster waste with low energy expenditure.