[en] The mechanical and structural characterization of the radioactive waste conditioning matrix is very important during the final disposal stage in the radioactive waste management cycle. The conditioning products should be a monolith with acceptable mechanical, chemical and physical properties that are maintained over an appropriate time such that the release of radioactivity from the waste form in the environment is minimized. The aim of this work is the XRD application for the phase identification of matrix that simulates the conditioned radioactive waste and the correlation with mechanical performance. The selected matrices for the study are normal cement with iron precipitates (hydroxide and phosphate), mineral additives (bentonite and volcanic tuff) and complexing agents (tartaric, citric and oxalic acids). The results obtained by this analysis give information about the chemical reactions between the radioactive precipitates and the hydrates, hydrolysis products of the cement. (author)