Estudo da alterabilidade de um basalto com argilomineral, na região de Toledo, Paraná

Abstract

The study of rock alteration is of great importance to evaluate the behavior of rocky material as a building material. Although much research has been developed in this area, the environment is constantly changing and its balance with engineering works must be considered for durability and safety reasons. However, since 2013 many national regulations were canceled and no replacements so far, among them are those related to investigation of the alterability of rocky aggregates. In this sense, this work had as objective to present a routine of field and laboratory tests to identify the variety and degree of expansibility of a clay minerals present in the rocky matrix of a basalt of the region of Toledo, Paraná. The composition identification of the basalt and the secondary mineral present in the rock matrix were performed by tactile-visual analysis, petrography and by the Scanning Electron Microscopy (MEV/EDS). The alterability and expansibility characterization of basalt were performed by means of expansion pressure test, natural and accelerated cycling (water-greenhouse and ethylene glycol). With the chemical and mineralogical composition analysis of the basalt under study, it is believed that the clay mineral is of the chlorite species, which has low expansibility through exposure to water and reactive expansion to ethylene glycol. In this way, it explains the reason why both the natural and accelerated cycling with water-greenhouse material alteration was minimal (weight loss less than 3%), unlike the cycling test with ethylene glycol (weight loss greater than 45%). In relation to the expansion pressure test, there was only an increase in volume for the samples submitted to ethylene glycol, and its expansion potential was considered to be very low (less than 2%). Thus, although classified as low alterability in the natural environment, there is the potential for rock disintegration in more aggressive environments and for its use in engineering works it is necessary to list the anthropic and weathering agents and to assess the potential risks for each situation.