Verificação do potencial de ativação alcalina de rochas vulcânicas ácidas: um estudo de desempenho mecânico e caracterização do ligante

Abstract

Alkali-activated ligands are produced from the reaction between aluminosilicate precursors and an alkaline activating solution. Despite the current development of these used as supplemental cementitious materials precursors of the Portland cement industry, alternative natural sources can be explored. One of these sources is constituted by the acid volcanic resources of the Paraná Magmatic Province (PMP), which present a favorable chemical and mineralogical composition for the production of binders. However, due to the scarcity of studies alluding to their use, the gap addressed with the aim of investigating the relationship between the development of alkali-activated ligands and the chemical-mineralogical characterization of acidic volcanic rocks with a vitreous character, found south of the PMP, is outlined . Three rocks were used and quantitatively characterized for chemical and mineralogical composition, geological formation and physical form after comminution. In order to assess its potential, different activation conditions were used: with and without addition of extra soluble silicates, with and without addition of CaO and two hydrothermal curing temperatures. Activation susceptibility was evaluated by mechanical development, geopolymerization consolidation, X-ray diffraction and efflorescence appearance analysis. The results showed that the activation potential of rocks is influenced by the chemical composition of the amorphous fraction of the precursors. It was noticed that the matrices are improved with the insertion of the CaO source due to the mechanical behavior and consolidation of geopolymerization, however, with regard to efflorescence, larger outcrops were identified with the addition of CaO. As for the temperature, it was noticed that this does not influence the consolidation of geopolymerization, but induces better mechanical performance. The source of soluble silicates leads to better mechanical strength, but does not contribute to the consolidation of activation, indicating the formation of unstable products that do not represent geopolymers. Finally, it can be seen that it is possible to produce stable matrices from the studied rocks, indicating better results with the superposition of the effects of the temperature of 80 °C in the cure and addition of CaO.