Unitary Portland cement, as well as mixed silicates binders derived from it, can constitute effective matrices for the immobilization of some hazardous substances containing heavy metals. The efficiency evaluation of the inertization procedure of noxious wastes/substances with heavy metals content in binding matrices should be considered according to the capacity of solidification/stabilization of heavy metal into the binders in which there are embedded, and also to the influences exerted toward the hardened system. Based on that, the controlled disposal of hazardous wastes might be assured through their solidification/stabilization into binding matrices, or eventually, the concretes which contain them could be used for roads infrastructure. This paper presents data regarding the influence of zinc, added as salts, onto the properties of some binding systems based on Portland cement and Portland cement with 30% granulated blast furnace slag.