Beside traditionali binders – Portland cement  and blended cements, the binders of type alkali activated  slag (AAS) and geopolymer can represent efficient matrices for immobilization of noxious substances.

                The present paper brings informations regarding the phisical and chemical processes at the hardening of alkali-activated slag and geopolymer, in which a waste with Pb content  was immobilised. Geopolymer binder was prepared using a fly ash and as activator – a mixture of  Na₂O.nSiO₂ and NaOH with silica modulus of 1.12. Alkali activated slag binders,were prepared with the same alkali-activator.

                This type of binders have a good immobilization capacity of the glass waste resulted from discarded cathode ray tube (CRT) with Pb content, added in amounts corresponding to 0.18-10% Pb. The inclusion of Pb²⁺ ions into the binding systems determines a certain retarding influence on the hardening processes, the effect being more intense for shorter periods of hardening and for higher amounts of Pb. The X-ray difraction data sugests the formation of a complex aluminosilicate with Pb content.