Geotechnical characterization of coal ash and its use as waterproofing barriers

ABSTRACT

In order to adapt to the reality of contemporary society, the organization of any and all productive processes should include waste management plans, which seek to find technical, economic and environmentally viable alternatives to the by-products arising from its operation. Under this premise the companies Energia Pecém and Eneva, which manage the Porto Pecém I and II thermoelectric plants, entered into a partnership with the Federal University of Ceará, aiming at the development of a scientific project that aimed to provide adequate destinations for the residues arising from the burning of coal in the thermoelectric plants. The result was the development of several works that evaluated alternatives for the use of ashes. The present study verified the possibility of using the ashes in layers of waterproofing barriers of landfills (liners). Several geotechnical tests were carried out in order to characterize the material and verify if it has the necessary properties for the proposed use, such as hydraulic conductivity, which for this purpose should be less than 10^-7 cm/s. However, significant variability was observed in the values of the studied parameters, which led to the need to analyze the use of a composite material, mixtures of soil (clayey sand) and composite ash in different proportions, which presented more consistent results, reaching hydraulic conductivity values close to those required for use as a liner. Among the mixtures of soil and ash analyzed, a mixture called S70C30 (70% soil mass and 30% ash mass) had a saturated permeability coefficient of 4.26x10^-7 cm/s which together with other geotechnical characteristics, was adequate for the proposed use.

Key-words
Ash; geotechnics; waterproofing barriers; permeability