Avaliação das cinzas de carvão mineral produzidas em usina termelétrica para construção de camadas de pavimentos

Abstract

The use of residues produced in thermoelectric plants can represent an alternative for the construction of economical and environmentally sustainable pavements. This research aims to evaluate the use of mineral coal ashes from a thermoelectric plant in granular layers of pavements, from laboratory studies and mechanistic-empirical analysis. Initially, the heterogeneity of the ashes arranged in a landfill was investigated from a 32-hole drilling and physical, chemical and environmental characterization tests, as well as mechanical tests on all collected samples. Due to the heterogeneity, the mechanical results obtained and the environmental necessity to inert the residue, a regional soil and a chemical stabilizer were selected to produce in laboratory stabilized mixtures that presented adequate mechanical and hydraulic properties for granular layers of pavements. Thus, mixtures of soil-ash (50% soil + 50% ash), ash-lime and soil + ash + lime were produced, in the proportion of 1%, 3% and 5% of the chemical stabilizer. For these mixtures, Proctor, CBR (California Bearing Ratio), MR (Resilience Module), RCS (Simple Compression Resistance) and RTCD (Tensile Strength by Diametral Compression) tests were carried out at different curing times (0, 7, 14 and 28 days). In addition, bituminous prime coat quality tests were conducted. It was verified, from the tests performed, that M3 (50% soil + 50% ash), M4 (95% ash + 5% lime) and M5 (47,5% ash + 47,5% soil + 5% lime) showed compatible mechanical behavior for use in layers of pavements. For these mixtures, Permanent Deformation tests and environmental tests were performed on samples in the loose state (leaching and solubilization) and in the compacted state (leaching in Column). Subsequently, pavement structures were designed by a mechanistic-empirical method, for different volumes of traffic, with the best mixtures investigated, proceeding a comparative cost analysis. It was concluded that the reutilization of thermoelectric residues in paving is feasible from the technical-financial and environmental point of view, representing potential alternative for proposing a more economical and sustainable pavement structural design.