Desenvolvimento de rocha aglomerada com matriz polimérica a partir de resíduos da mineração de opala de Pedro II-PI

Abstract

Opal mining in Pedro II, Piauí, is a traditional activity that generates large amounts of waste, usually discarded with no proper management or reuse. This study proposes the development of an agglomerated stone produced from this waste combined with epoxy resin, targeting applications in civil construction. The waste was comminuted, classified into three particle size ranges, and used to produce plates molded by uniaxial compression, with a composition of 20% epoxy resin and 80% waste, following a Simplex-Lattice experimental design. Waste characterization was carried out using X-ray diffraction (XRD) and X-ray fluorescence (XRF), while the molded specimens were tested for apparent density, porosity, water absorption, and three-point flexural strength, in accordance with ABNT NBR 15845-2 (2015) and UNE-EN 14617-1 (2013). In addition, Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) was performed on specimens with the highest (composition 7) and lowest (composition 3) flexural strength, to investigate the morphology and distribution of the polymeric matrix constituents. The results revealed high silica and alumina contents, as well as the presence of quartz, albite, and kaolinite. Compositions 2, 7, 8, and 9 met the requirements of ABNT NBR 15844 (2015), with porosity ≤ 1.0% and water absorption ≤ 0.4%, confirming their technical feasibility for use as coatings. SEM-EDS images corroborated the minerals identified by XRD, showing improved compaction and particle distribution in composition 7 compared to composition 3. The latter exhibited greater loss of properties due to manual processing, as evidenced by resin irregularities and poorly integrated grains. This heterogeneity explains its lower mechanical performance. Overall, the findings indicate a sustainable alternative for reusing mining waste, contributing to regional development. They also highlight the material’s technical potential and reinforce the importance of practices that promote circular economy and sustainability, while adding value to a mineral residue abundant in the region.