Desenvolvimento de concretos sustentáveis através da aplicação do pó das escamas da tilápia do Nilo

Abstract

Up to 70% of a fish's total weight is discarded during processing; 5% of this consists of scales—composed primarily of collagen and hydroxyapatite—which possess adsorptive properties and can serve as raw material for various useful products. Incorporating fish scale powder into cementitious materials can contribute to the sustainability of both the fishing and construction industries by enhancing properties such as mechanical strength; the scales' adsorption characteristics may facilitate slower internal curing of the concrete. This study aimed to characterize Nile tilapia scale powder and to evaluate the fresh-state consistency and compressive strength of concrete mixes containing this additive. The concrete specimens were subjected to two curing methods—dry (air) and wet (water-submerged)—and tested at 7, 28, and 91 days. Scales were collected from a fish processing plant in the Itaporã (MS) region, washed, dried, and ground in a knife mill to produce a fine powder. The powder underwent loss-on-ignition and X-ray diffraction (XRD) analyses. Concrete specimens (10x20 cm) were produced using a reference mix ratio of 1:2.1:2.92 (cement:sand:coarse aggregate) and a water/cement ratio of 0.7, without admixtures; scale powder was added at levels of 0%, 2.5%, 5%, 7.5%, and 10% by weight of cement. The results indicated that water-cured concrete consistently outperformed air-cured concrete. Additions of up to 5% scale powder resulted in increased mechanical compressive strength at 28 days compared to the reference sample; air-cured concretes showed a 2.5% gain, while water cured concretes showed an increase of 3.34%. Although the powder addition reduces the consistency and workability of fresh concrete, utilizing this waste would offer environmental benefits by reducing the volume of waste discarded by the fish processing industry. It was concluded that incorporating Nile tilapia scale powder into cementitious materials could be an interesting and viable alternative for producing sustainable concrete; however, it is important to note that this area of research is still evolving. Therefore, further studies are needed to evaluate the effectiveness and safety of this technique for large-scale application in civil construction.