THE INFLUENCE OF HEAVY-METALS ON THE HYDRATION OF BINDERS OF INTEREST FOR CHEMICAL GYPSUM STABILIZATION

The effects of the presence of some heavy metals on the hydration processes of binders useful for waste stabilisation have been investigated. The specific types of waste to which our attention has been directed are the chemical gypsums formed as by-products in a number of industrial processes. Experiments have been carried out with hydratory model systems containing a binder (blast-furnace slag or fly ash-lime mixture), pure gypsum and a heavy metal compound (Cr(OH)3, K2CrO4, Mn(OH)3, Fe(OH)3, Ni(OH)2, Cu(OH)2, Cd(OH)2 or Zn(OH)2). The results have shown that in most cases the hydration processes are substantially unchanged or even favourably influenced. Retarding effects were only observed in the presence of Zn and (to a lesser extent) Cu. © 1990.