EAF slag could be re-utilized as alternative stone material only if they are chemically stable in contact with water. The presence of hydraulic phases as larnite (2CaO.SiO2) could imply the releasing of dangerous elements into environment. Chemical treatment seems to be the only way to assure completely stable structure, especially for long-term application. Efficiency of silica addition during the deslagging period is presented in this study. Microstructural characterization of modified slag is performed by SEM and XRD analysis. Elution tests have been performed according to EN 12457-2 standard and the obtained results have been compared with and without silica addition. The obtained results demonstrate the reliability of the proposed process.