Resumo:
With a focus on the circular economy, this study used commercial gypsum and sludge from the treatment of wastewater from mining processes at Nexa Resoures as the main materials. The technical and economic feasibility of reusing the sludge in the form of a blend (mixture of sludge and commercial gypsum) as a coating for civil construction were evaluated. The studies developed with this material consisted of evaluating the physical-chemical and mechanical properties of mixtures of sludge and commercial gypsum, with mass percentages of sludge in relation to pure commercial gypsum (control material) that varied between 10%, 20%, 30%, 40% and 50%. In order to delay the setting time of the blend, the additive Blok gypsum was used and subsequently citric acid, which indicated efficiency as a setting retardant, and was also cheaper than the additive. The samples were characterized in powder form through thermal, mineralogical and granulometric analyses. In the fresh state through analysis of the setting times. And in the hardened state through compression and tensile strength tests. The economic feasibility analysis was carried out by the junior company FEA Junior of USP - SP, which, through specialists, carried out the plaster market study, considering the market in Peru. The results suggest that all the mixes were within ASTM C28/C28M for compression strength, and within NBR 13528-2 and EN 13279-1 for tensile adhesion strength. Although the 30% mix without additives met these standards, there were difficulties during the tests due to the short setting time. When applying the blend to the wall, according to the considerations of the hired applicator, the blends were easy to apply, but with apparently fast drying, which according to the professional is an advantage over commercial plaster. All the results suggest that the use of the blend as a wall covering in civil construction is technically feasible, however, for large-scale use, adjustments may be necessary. According to the economic feasibility analysis carried out by FEA Junior, the results indicate a promising market to direct the production of the blend, however, according to the studies, the application of the blend as an alternative product to plaster should not be limited to wall coverings only. The hypotheses of application in the production of Drywall and in the cement industry should also be considered, thus adding value to the product produced.
