Ciclagem acelerada de agregados de basalto em água saturada por dióxido de carbono

Abstract

Carbonation is a phenomenon resulting from the interaction between atmospheric carbon dioxide and water, forming carbonic acid and reacting with rock minerals, resulting in carbonates. In this sense, the present work seeks to quantify the changes in particle size and physical indices of the rock (density, porosity and water absorption), from laboratory cycling with water saturated by CO2 gas. Aggregates of particle size fraction between 6.3 and 9.5 mm were used, with three basalt compositions, which are: (i) massive gray basalt (BMC); (ii) massive basalt with the presence of clay minerals in its matrix (BMA); (iii) mixed field composition (CMC), consisting of 85% BMC sample and 15% BMA sample. The cycling tests were carried out using 12 cycling batteries, each battery lasting for 30 days with CO2 brine saturation, with weekly monitoring of pH, electrical conductivity and redox potential parameters, and 15 days of drying in the sun. Saturation water was obtained by bubbling CO2 gas into distilled water (20 minutes at 5 psi). BMA type aggregates were more susceptible to changes, with greater loss of mass, release of ions into water, depreciation of physical indices and became more friable to the touch in the last batteries. Massive basalt (BMC) also influenced particle size and physical indices, even if to a lesser extent. In general, three main issues can be verified, namely: (i) In the application of basalt as aggregates, especially for granular filters, it is necessary to consider the influence of CO2 in the alteration of the granulometry and in the geotechnical parameters of the rock; (ii) For the application of the rock in rockstone techniques, the presence of clay minerals is positive, as it accelerates the carbonation reactions; (iii) When the rocky material is destined for gas storage, with the objective of minimal impact on the rocky material, the presence of clay minerals should be investigated, as they are more susceptible to carbonation reactions.