Efeito da utilização de resíduos sólidos de rochas ornamentais do Seridó potiguar nas propriedades de argamassa autonivelante

Abstract

The mineral industry focused on the extraction of dimension stones has a positive impact on the economy of Seridó Norte Rio Grande. However, because it is a mineral extraction, a non-renewable natural resource, there is a paradox between keeping the economy functioning and, in turn, the environment in balance for present and future generations, as provided for in the Federal Constitution. Knowing that in the process of extracting and processing this raw material, solid waste is generated, including rock dust, this research seeks to mitigate the environmental impacts through the reuse of this waste; using it in the production of self-levelling mortar, in line with the 2030 Agenda through the Sustainable Development Goals. Self-levelling mortars are cementitious composites with particular spreading characteristics through their own weight, with high viscosity, low segregation and no exudation. In this context, the effect of adding 10, 20 and 30% of ornamental rock powder residue (RPRO), resulting from the improvement process as a raw material for self-levelling mortars, was evaluated, particularly in its rheological, physical-mechanical and microstructural properties . The RPRO used comes from the municipality of Parelhas-RN, which, after being collected, the sample was prepared for the physical-chemical and microstructural characterization through X-ray fluorescence tests (FRX), laser granulometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), fineness index, specific surface area, pore volume and pozzolanic activity index with Portland cement; as well as the characterization of the binder and fine aggregate. Subsequently, the pozzolanic activity index of the residue that was added was analyzed through its initial characterizations and the pozzolanic activity index test with Portland cement at 28 days. Tests were carried out with and without addition of residue, characterizing them through their rheological (fresh state), physical-mechanical and microstructural (hardened state) properties. For the first one, the mini slump, mini funnel-V, box L and flow retention were evaluated. Already in the hardened state, specific mass, water absorption by capillarity, water absorption by immersion, voids index, compressive strength, XRD and SEM. As a result, the residue – ornamental rock dust – acted as a filler in the self-levelling mortar, improving workability, viscosity and fluidity in the fresh state, having the characteristic of a viscosity modifier. In the hardened state, the compositions showed low water absorption by capillarity and by immersion, reduction in the voids index and high compressive strength, with the mixes with addition of 10%p. and 20%p. classified as of high mechanical resistance for floors, according to NBR 11801:2012, with values greater than 40Mpa. Thus, the research obtained a self-leveling mortar with the addition of RPRO with potential for application in the civil construction industry, with emphasis on the addition of 10% p. which obtained the best results; in addition to contributing to sustainable development.