Avaliação dos ciclos de alteração acelerada da NBR 12696:1992 para rocha basáltica

Abstract

Rocks are widely used in civil engineering works such as aggregates for concrete, rockfill, paving, railroad, among others. Often, the rock material is directly exposed to the environment, and durability studies are necessary to evaluate its resistance against weathering. Changes in the geotechnical properties of the rock are expected to occur over time. In this sense, the objective of this work was to present a routine of laboratory tests for the identification of the cycle time of samples of basaltic lithotypes, based on NBR 12696:1992, NBR 12697:1992 and the Water Absorption method adapted from Hamrol (1961). With the analysis of different times of water-greenhouse cycles for basaltic lithotypes, it was observed that the weight loss of the material was minimal (less than 4%), compared to the accelerated cycle test with Ethylene glycol (approximately 37%). Thus, it was possible to identify that the water-greenhouse cycle test was not representative to identify the alterability of the rock material, in contrast, the test with Ethylene glycol allowed to verify that even blocks of rock with good physical-mechanical qualities have undergone alteration throughout the time, especially those that presented clay minerals in their composition.