Sensitivity of ordinary rock weathering tests to acid rock drainage

It is well known that Acid Rock Drainage (ARD) is a major environmental concern for the mining and civil industry, due to water quality deterioration. Another important issue related to ARD is the integrity of the civil structures percolated by these effluents, especially concrete structures, rock fillings and rock filter/drainage layers. It is expected that the acidic nature of ARD can lead to accelerated weathering processes, reducing the time lifespan of these structures. In the present research we propose to evaluate the sensitivity of two of the most common laboratory rock weathering tests to acidic conditions, the Soxhlet Extractor and Soundness Test. Firstly, three different rock samples were characterized for mineralogy, petrography, and chemical composition. After, they were submitted to Soxhlet Extractor and Soundness (immersion) weathering tests, using ARD, distilled-deionized water (DDW) in the Soxhlet Extractor and ARD, DDW and sulfate as percolating/immersion solutions for the Soundness Test. The results showed that under the ordinary conditions used in these tests, no significant weather variation was observed among all the rocks samples and solutions. Thus, the hypotheses of more intense weathering due to the ARD influence was not corroborated.