[en] To solve the actual environmental problems, one solution is to reuse industrial residues in other areas as the civil construction. The EVA is a residue from footwear industry that can be used in civil construction as lightweight aggregate in mortar mixtures to use in nonstructural parts. However, studies have shown a reduction of mechanical strength when the EVA is added if compared to conventional mixtures. To solve the problem, the use of natural fibers as the piassava is considered. This paper describes an application of Fourier analysis in the micro-tomographic images for the characterization of the lightweight mortar mixtures. Using the Fourier spectrum, considering the amplitude, the positions of the peaks and the histograms, is possible to identify the presence of the aggregates in the mixtures. These results have allowed to consider, Fourier analysis as a material characterization tool that's not depends on geometrical parameters. (author)