Avaliação da heterogeneidade de cinzas de carvão mineral advindas da termelétrica energia pecém e sua aplicação em camadas granulares de pavimentos

Abstract

In the face of a global scenario in which the development of an environmental ethic and eco-efficient industrial systems is encouraged, the use of wastes as new construction materials is imperative. Considering this challenge, this study investigated the use of mineral coal ash from a thermoelectric power plant as granular layers in pavements. It was evaluated the heterogeneity of the ashes stored in a sedimentation basin. Thirty-two samples were collected and had physical (gradation and limits of liquidity / plasticity tests), chemical and environmental (solubilization and leaching tests) characteristics tested, as well as mechanical characteristics by compaction and CBR tests that were carried out for all the samples. Chemical dangerousness was observed in six samples, being the others classified as class II-A (non-inert) waste. Optimal moisture values were obtained between 22.5% and 57%, with an average of 38%. Variation was also observed in CBR tests, from 1% to 46%, with about 80% of the samples presenting values below the minimum required for use in subbase layers. Expansion values oscillated from 0.23% to 8.60%, showing that 50% of the collected samples did not meet the minimum requirement granular layers. As observed a significant heterogeneity from the original material, mixes of ashes from various points of collection with regional soil were produced as an alternative to improve the mechanical behavior of the material and make it suitable for the expected use. A mechanic-empirical method was used to design a pavement with the investigated mixes and a comparative cost analysis was performed. The mixes proved to be feasible in a technical, economic and environmental point of view for use in pavement layers. It was concluded that the use of ashes in pavements represents an important engineering solution to give a technical and environmentally correct purpose to the wastes from thermoelectric power plants.