Análise comparativa das propriedades físicas, mecânicas e tecnológicas das rochas de uma pedreira em Itaara/RS

Abstract

Using rocks as building materials is an ancient practice of mankind. Its use is comprehensive even today, due to several factors: high qualities of durability, strength and generally low cost. For building uses that do not require aesthetic qualities (for example, rocks that are not going to be used for finishing and coatings) and use large volumes of rock, these rocks are usually sought close to the work. Therefore, it is important to study and analyze the properties of the rocks available around the project. This is done to make the best use possible, reducing costs of the work and possible errors. The present work seeks to make a comparative analysis of the physical, mechanical and technological properties of the rocks of the city of Itaara / RS, which serve the construction market of the central region of the state of Rio Grande do Sul. The rocks of the Brita Pinhal quarry were studied. Part of the city of Itaara / RS presents predominance of basic and acidic effusive rocks of the Serra Geral formation: basalts and rhyolites. The Brita Pinhal Quarry is on the edge of the flows that make up the occurrences of these effusive rocks. In this context, one of the objectives, besides the analysis of the rocks for use as building materials is to identify the reasons why the Brita Pinhal quarry rocks have high absorption (when compared to rocks from other quarries in the same region). For this, technical visits, geotechnical tests, as well as preparation of thin sections and petrographic analyzes were carried out.As for the results, values of actual and apparent specific mass, absorption, apparent porosity and degree of compactness for 3/8 "(9.5 mm) gravel sizes were obtained. By the graphs corresponding to these tests, it was observed that, for bench 2, inflection points are verified, indicating counterintuitive variability in the results, being verified higher values in the scope of the degree of compactness, and lower values for absorption and apparent porosity. This behavior can be explained by the types of rocks that make up this bench, these being the least altered rocks of the mining front. Another possibility is that these rocks have a smaller amount of glass. When integrating the petrographic analysis, the study of the regional geology with technological tests for the characterization of the rock mass, it was possible to recognize that the rocks closer to the top of the mining front have a greater absorption, these also possessing more glass and greater alterability. As a result, they absorb more water. As a secondary conclusion, it was verified that the upper rocks are basalts and the lower rocks of a dacite.